The AZEK Company Inc. (AZEK) 10-K29 Nov 232023 FY Annual reportFinancial data

Company Profile

Cover Page

Cover Page - USD ($) $ in Thousands	12 Months Ended
Cover Page - USD ($) $ in Thousands	Sep. 30, 2023	Oct. 31, 2023	Mar. 31, 2023
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2023
Document Period End Date	Sep. 30, 2023
Current Fiscal Year End Date	--09-30
Entity Registrant Name	AZEK Co Inc.
Entity Central Index Key	0001782754
Entity File Number	001-39322
Entity Tax Identification Number	90-1017663
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Incorporation, State or Country Code	DE
Entity Emerging Growth Company	false
Entity Address, Address Line One	1330 W Fulton Street, Suite 350
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60607
City Area Code	877
Local Phone Number	275-2935
Title of 12(b) Security	Class A Common Stock, par value $0.001 per share
Trading Symbol	AZEK
Security Exchange Name	NYSE
Entity Public Float			$ 2,796,678,033
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Auditor Name	PricewaterhouseCoopers LLP
Auditor Firm ID	238
Auditor Location	Chicago, Illinois
Common Class A [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		147,699,313
Common Class B [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		100

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Current assets:
Cash and cash equivalents	$ 278,314	$ 120,817
Trade receivables, net of allowances	57,660	90,159
Inventories	221,101	299,905
Prepaid expenses	13,595	17,212
Other current assets	12,300	2,501
Total current assets	582,970	530,594
Property, plant and equipment, net	501,023	517,913
Goodwill	994,271	993,995
Intangible assets, net	199,497	245,835
Other assets	87,793	94,754
Total assets	2,365,554	2,383,091
Current liabilities:
Accounts payable	56,015	48,987
Accrued rebates	60,974	50,479
Accrued interest	260	4,436
Current portion of long-term debt obligations	6,000	6,000
Accrued expenses and other liabilities	71,994	72,589
Total current liabilities	195,243	182,491
Deferred income taxes	56,330	65,195
Long-term debt — less current portion	580,265	584,879
Other non-current liabilities	104,073	106,083
Total liabilities	935,911	938,648
Commitments and contingencies (Note 17)
Stockholders’ equity:
Preferred stock, $0.001 par value; 1,000,000 shares authorized and no shares issued and outstanding at September 30, 2023 and September 30, 2022, respectively
Additional paid-in capital	1,662,322	1,630,378
Accumulated deficit	(45,047)	(113,002)
Accumulated other comprehensive income (loss)	1,878
Treasury stock, at cost, 8,268,423 shares at September 30, 2023 and 4,116,570 shares at September 30, 2022	(189,666)	(73,088)
Total stockholders’ equity	1,429,643	1,444,443
Total liabilities and stockholders’ equity	2,365,554	2,383,091
Common Class A [Member]
Stockholders’ equity:
Common stock	$ 156	$ 155

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2023	Sep. 30, 2022
Preferred stock, par value per share	$ 0.001	$ 0.001
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Treasury stock, shares	8,268,423	4,116,570
Common Class A [Member]
Common stock, par value per share	$ 0.001	$ 0.001
Common stock, shares authorized	1,100,000,000	1,100,000,000
Common stock, shares issued	155,967,736	155,157,220
Common stock, shares outstanding	147,699,313
Common Class B [Member]
Common stock, par value per share	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	100	100
Common stock, shares outstanding	100	100

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net sales	$ 1,370,316	$ 1,355,586	$ 1,178,974
Cost of sales	932,663	946,266	789,023
Gross profit	437,653	409,320	389,951
Selling, general and administrative expenses	305,162	279,889	244,205
Other general expenses	1,065		2,592
Loss on disposal of plant, property and equipment	249	496	1,025
Operating income	131,177	128,935	142,129
Other expenses:
Interest expense, net	39,293	24,956	20,311
Total other expenses	39,293	24,956	20,311
Income (loss) before income taxes	91,884	103,979	121,818
Income tax expense	23,929	28,754	28,668
Net income	67,955	75,225	93,150
Other comprehensive income:
Unrealized gain due to change in fair value of derivatives, net of tax	1,878
Total other comprehensive income	1,878
Comprehensive income	$ 69,833	$ 75,225	$ 93,150
Net income per common share:
Basic	$ 0.45	$ 0.49	$ 0.61
Diluted	$ 0.45	$ 0.49	$ 0.59
Weighted average shares used in calculating net income per common share:
Basic	150,162,256	153,510,110	153,777,859
Diluted	150,849,896	154,517,843	156,666,394

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Class A [Member]	Common Class B [Member]	Common Stock [Member] Common Class A [Member]	Common Stock [Member] Common Class B [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Sep. 30, 2020	$ 1,303,888				$ 155			$ 1,587,208	$ (283,475)
Beginning balance (in shares) at Sep. 30, 2020					154,637,240
Beginning balance (in shares) at Sep. 30, 2020						100
Adoption of Accounting Standard Update (ASU) \| ASU 2016-02 [Member]		$ 2,098								$ 2,098
Net Income (Loss)	93,150								93,150
Stock-based compensation	22,250							22,250
Vesting of restricted stock (in shares)					14,681
Exercise of vested stock options	5,988							5,988
Exercise of vested stock options (in shares)					260,338
Cancellation of restricted stock awards (in shares)					(45,946)
IPO costs	(210)							(210)
Ending balance at Sep. 30, 2021	1,427,164				$ 155			1,615,236	188,227
Ending balance (in shares) at Sep. 30, 2021					154,866,313
Ending balance (in shares) at Sep. 30, 2021						100
Net Income (Loss)	75,225								75,225
Stock-based compensation	17,971							17,971
Exercise of vested stock options	5,995							5,995
Exercise of vested stock options (in shares)					260,649
Cancellation of restricted stock awards (in shares)					(16,425)
Issuance of common stock under employee stock plan, net of shares withheld for taxes	(429)							(429)
Issuance of common stock under employee stock plan, net of shares withheld for taxes (in shares)					46,683
Treasury stock purchases	(81,483)						$ (73,088)	(8,395)
Treasury stock purchases (in shares)							4,116,570
Ending balance at Sep. 30, 2022	1,444,443				$ 155		$ (73,088)	1,630,378	(113,002)
Ending balance (in shares) at Sep. 30, 2022					155,157,220
Ending balance (in shares) at Sep. 30, 2022			155,157,220	100			4,116,570
Ending balance (in shares) at Sep. 30, 2022						100
Net Income (Loss)	67,955								67,955
Other comprehensive income	1,878										$ 1,878
Stock-based compensation	18,518							18,518
Exercise of vested stock options	14,955				$ 1			14,954
Exercise of vested stock options (in shares)					650,138
Cancellation of restricted stock awards (in shares)					(19,306)
Issuance of common stock under employee stock plan, net of shares withheld for taxes	(1,528)							(1,528)
Issuance of common stock under employee stock plan, net of shares withheld for taxes (in shares)					179,684
Treasury stock purchases	(116,578)						$ (116,578)
Treasury stock purchases (in shares)							4,151,853
Ending balance at Sep. 30, 2023	$ 1,429,643				$ 156		$ (189,666)	$ 1,662,322	$ (45,047)		$ 1,878
Ending balance (in shares) at Sep. 30, 2023					155,967,736
Ending balance (in shares) at Sep. 30, 2023			155,967,736	100			8,268,423
Ending balance (in shares) at Sep. 30, 2023						100

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Operating activities:
Net Income (Loss)	$ 67,955	$ 75,225	$ 93,150
Adjustments to reconcile net income to net cash flows provided by (used in) operating activities:
Depreciation expense	86,206	67,996	51,802
Amortization expense	46,338	50,537	49,802
Non-cash interest expense	1,647	5,638	3,110
Non-cash lease expense	(251)	(275)	(88)
Deferred income tax expense (benefit)	(9,487)	19,684	25,529
Non-cash compensation expense	18,518	27,512	22,250
Loss on disposal of plant, property and equipment	2,220	496	1,025
Bad debt provision	731	290	342
Changes in operating assets and liabilities:
Trade receivables	31,768	(8,545)	(6,772)
Inventories	78,688	(97,459)	(58,819)
Prepaid expenses and other current assets	(3,675)	(4,300)	(5,892)
Accounts payable	22,596	(32,146)	16,071
Accrued expenses and interest	17,416	(1,345)	14,910
Other assets and liabilities	1,872	2,527	1,259
Net cash provided by operating activities	362,542	105,835	207,679
Investing activities:
Purchases of property, plant and equipment	(88,545)	(170,938)	(175,119)
Proceeds from sale of property, plant and equipment	202	649	46
Purchases of intangible assets		(1,500)
Acquisitions, net of cash acquired	(161)	(108,387)
Net cash provided by investing activities	(88,504)	(280,176)	(175,073)
Financing activities:
Proceeds under Revolving Credit Facility	25,000	40,000
Payments under Revolving Credit Facility	(25,000)	(40,000)
Payments of financing fees related to Term Loan Agreement			(939)
Payments of Term Loan Agreement	(6,000)	(467,654)
Proceeds from 2022 Term Loan Agreement		595,500
Repayments of finance lease obligations	(2,619)	(3,865)	(1,921)
Payments of INTEX contingent consideration	(5,850)
Payments of initial public offering related costs			(210)
Exercise of vested stock options	14,954	5,995	5,988
Cash paid for shares withheld for taxes	(1,528)	(429)
Purchases of treasury stock	(115,498)	(81,483)
Net cash provided by (used in) financing activities	(116,541)	44,622	2,918
Net increase (decrease) in cash and cash equivalents	157,497	(129,719)	35,524
Cash and cash equivalents at beginning of period	120,817	250,536	215,012
Cash and cash equivalents at end of period	278,314	120,817	250,536
Supplemental cash flow disclosure:
Cash paid for interest, net of amounts capitalized	41,728	14,899	17,119
Cash paid for income taxes, net	34,480	10,549	4,620
Supplemental non-cash investing and financing disclosure:
Capital expenditures in accounts payable at end of period	7,703	29,562	16,177
Right-of-use operating and finance lease assets obtained in exchange for lease liabilities	$ 3,830	33,400	$ 57,817
2022 Term Loan Agreement [Member]
Financing activities:
Payments of debt issuance costs		$ (3,442)

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ 67,955	$ 75,225	$ 93,150

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	12 Months Ended
Organization and Summary of Significant Accounting Policies	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Summary of Significant Accounting Policies	1. ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES a. Organization The AZEK Company Inc. (the “Company”) is a Delaware corporation that holds all of the limited liability company interests in The AZEK Group LLC (f/k/a CPG International LLC), the entity which directly and indirectly holds all of the equity interests in the operating subsidiaries and which changed its name from CPG International LLC to The AZEK Group LLC on August 1, 2023. The Company is an industry-leading designer and manufacturer of beautiful, low-maintenance and environmentally sustainable building products for residential, commercial and industrial markets. The Company’s products include decking, railing, trim, porch, moulding, pergolas, outdoor furniture, bathroom and locker systems, as well as extruded plastic sheet products and other non-fabricated products for special applications in industrial markets. The Company operates in various locations throughout the United States. The Company’s residential products are primarily branded under the brand names AZEK ® , TimberTech ® , VERSATEX ® , ULTRALOX ® , StruXure and INTEX ® , while the commercial products are branded under the Vycom ® brand names Celtec ® , Playboard ® , Seaboard ® , Flametec ® , Designboard ® , Corrtec, Timberline ® , and Scranton Products ® brand names including Aria Partitions ® , Eclipse Partitions ® , Hiny Hiders ® partitions, Tufftec Lockers ® and Duralife Lockers ® . Secondary Offerings On January 26, 2021, the Company completed an offering of 23,000,000 shares of Class A common stock, par value $ 0.001 per share, including the exercise in full by the underwriters of their option to purchase up to 3,000,000 additional shares of Class A common stock, at a public offering price of $ 40.00 per share. The shares were sold by certain of the Selling Stockholders. The Company did not receive any of the proceeds from the sale of the shares by those Selling Stockholders. In connection with the offering, the Company incurred approximately $ 1.2 million in expenses. On June 1, 2021, the Company completed an offering of 17,250,000 shares of Class A common stock, par value $ 0.001 per share, including the exercise in full by the underwriters of their option to purchase up to 2,250,000 additional shares of Class A common stock, at a public offering price of $ 43.50 per share. The shares were sold by certain of the Selling Stockholders. The Company did not receive any of the proceeds from the sale of the shares by those Selling Stockholders. In connection with the offering, the Company incurred approximately $ 1.1 million in expenses. During the three months ended June 30, 2023, the Company completed an offering of 16,100,000 shares of Class A common stock, par value $ 0.001 per share, including the exercise in full by the underwriter of its option to purchase up to 2,100,000 additional shares of Class A common stock, at a public offering price of $ 24.36 per share. The shares were sold by certain of the Selling Stockholders. The Company did not receive any of the proceeds from the sale of the shares by those Selling Stockholders. In connection with the offering the Company incurred approximately $ 1.1 million in expenses. In connection with the offering, the Company agreed to purchase from the underwriter 1,477,832 shares of its Class A common stock being sold by the Selling Stockholders to the underwriter at a price per share equal to the price being paid by the underwriter to the Selling Stockholders, resulting in an aggregate purchase price of approximately $ 36.0 million. b. Summary of Significant Accounting Policies Basis of Presentation The Company operates on a fiscal year ending September 30. The accompanying Consolidated Financial Statements and notes have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The Consolidated Financial Statements include the assets, liabilities and results of operations of the Company and its wholly owned subsidiaries. All material intercompany transactions and balances have been eliminated in consolidation. The Company’s financial condition and results of operations are affected by a number of factors, including, but not limited to, the cost to manufacture and distribute products, cost of raw materials, inflation, consumer spending and preferences, interest rates, the impact of any supply chain disruptions, economic conditions, and/or any adverse effects from global health pandemics, geopolitical conflicts and other factors beyond the Company’s control. Management cannot predict the degree to, or the period over, which the Company may be affected by such factors. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Significant estimates include revenue recognition, reserves for excess inventory, inventory obsolescence, inventory valuation, product warranties, customer rebates, stock-based compensation, litigation, income taxes, contingent consideration, goodwill and intangible asset valuation and accounting for long-lived assets. Management’s estimates and assumptions are evaluated on an ongoing basis and are based on historical experience, current conditions and available information. Actual results may differ from estimated amounts. Estimates are revised as additional information becomes available. Seasonality Although the Company generally has demand for its products throughout the year, its sales have historically experienced some seasonality. The Company has typically experienced higher levels of sales of its residential products in the second fiscal quarter of the year as a result of its “early buy” sales, which encourages dealers to stock its residential products. The Company has generally experienced lower levels of sales of residential products in the first fiscal quarter due to adverse weather conditions in certain markets during the winter season. Although its products can be installed year-round, weather conditions can impact the timing of the sales of certain products. In addition, the Company has experienced higher levels of sales of its bathroom partition products and its locker products during the second half of its fiscal year, which includes the summer months when schools are typically closed and therefore are more likely to undergo remodel activities. Revenue Recognition The Company sells its products to residential and commercial markets. The Company’s Residential segment principally generates revenue from the manufacture and sale of its premium, low-maintenance composite decking, railing, trim, moulding, pergolas and cabanas and accessories. The Company’s Commercial segment generates revenue from the sale of its partition and locker systems along with plastic sheeting and other non-fabricated products for special applications in industrial markets. The Company recognizes revenues when control of the promised goods is transferred to the Company’s customers in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods, at a point in time, when shipping occurs. Each product the Company transfers to the customer is considered one performance obligation. The Company has elected to account for shipping and handling costs as activities to fulfill the promise to transfer the goods. As a result of this accounting policy election, the Company does not consider shipping and handling activities as promised services to its customers. Shipping and handling costs billed to customers are recorded in net sales. The Company records all shipping and handling costs as “Cost of sales”. Customer contracts are typically fixed price and short-term in nature. The transaction price is based on the product specifications and is determined at the time of order. The Company does not engage in contracts greater than one year, and therefore does not have any incremental costs capitalized as of September 30, 2023 or September 30, 2022. The Company may offer various sales incentive programs throughout the year. It estimates the amount of sales incentive to allocate to each performance obligation, or product shipped, using the most-likely-amount method of estimation, based on sales to the direct customer or sell-through customer. The estimate is updated each reporting period and any changes are allocated to the performance obligations on the same basis as at inception. Changes in estimate allocated to a previously satisfied performance obligation are recognized as part of net revenue in the period in which the change occurs under the cumulative catch-up method. In addition to sales incentive programs, the Company may offer a payment discount, if payments are received within 30 days. The Company estimates the payment discount that it believes will be taken by the customer based on prior history and using the most-likely-amount method of estimation. The Company believes the most-likely-amount method best predicts the amount of consideration to which it will be entitled. The payment discounts are also reflected as part of net revenue. The total amount of incentives were $ 132.6 million , $ 105.8 million and $ 92.5 million for the years ended September 30, 2023, 2022 and 2021, respectively. The Company records deferred revenue when cash payments are received or due in advance of the Company’s performance. Earnings Per Share Basic net income per common share is computed based on the weighted average number of common shares outstanding. Potentially dilutive shares are included in the diluted per-share calculations using the treasury stock method for the periods in fiscal year 2020 when the effect of their inclusion is dilutive. Refer to Note 15 for additional information. Advertising Costs Advertising costs primarily relate to trade publication advertisements, cooperative advertising, product brochures and samples. Such costs are expensed as incurred and are included in “Selling, general and administrative expenses” within the Consolidated Statements of Comprehensive Income. Total advertising expenses were approximately $ 62.2 million , $ 52.5 million and $ 37.8 million for the years ended September 30, 2023, 2022 and 2021 , respectively. Research and Development Costs Research and development costs primarily relate to new product development, product claims support and manufacturing process improvements. Such costs are expensed as incurred and are included in “Selling, general and administrative expenses” within the Consolidated Statements of Comprehensive Income. Total research and development expenses were approximately $ 9.2 million , $ 9.5 million , and $ 7.4 million , for the years ended September 30, 2023, 2022 and 2021 , respectively. Cash and Cash Equivalents The Company considers cash and highly liquid investments with an original maturity of three months or less to be cash and cash equivalents. Cash and cash equivalents are stated at cost, which approximates or equals fair value due to their short-term nature. Concentrations and Credit Risk The Company’s financial instruments that are exposed to concentrations of credit risk consist primarily of cash and cash equivalents and trade accounts receivable. As of September 30, 2023, cash and cash equivalents were maintained at major financial institutions in the United States, and current deposits are in excess of insured limits. The Company believes these institutions have sufficient assets and liquidity to conduct their operations in the ordinary course of business with little or no credit risk to the Company. The Company has not experienced any losses in such accounts. Sales to certain Residential segment distributors accounted for 10 % or more of the Company’s total net sales in 2023, 2022 and 2021 were as follows: Years Ended September 30, 2023 2022 2021 Distributor A 18.7 % 19.3 % 23.3 % At September 30, 2023 , receivables from one customer represented 17.2 % of gross trade receivables. At September 30, 2022 , two customers each represented more than 10 % of gross trade receivables: Customer A was 10.6 % and Customer B was 14.8 %. For each year ended September 30, 2023, 2022 and 2021 , approximately 17 %, 16 % and 18 %, respectively, of the Company’s materials purchases were purchased from its largest supplier. Allowance for losses The Company routinely assesses the financial strength of its customers and believes that its trade receivables credit risk exposure is limited. The allowance for losses is our estimate of credit losses associated with trade receivables balances. An estimate of expected credit losses is recognized as a valuation allowance and adjusted each reporting period. The estimate is based on the current expected credit loss model and is determined by management in the course of regularly evaluating individual customer receivables. This evaluation takes into consideration a customer’s financial condition and credit history, as well as current economic conditions. Amounts are written-off if and when they are determined to be uncollectible. Inventories Inventories (mainly petrochemical resin in raw materials and finished goods), are valued at the lower of cost or net realizable value and are reduced for slow-moving and obsolete inventory. Management assesses the need for, and the amount of, obsolescence write-down based on customer demand of the item, the quantity of the item on hand and the length of time the item has been in inventory. Further, management also considers net realizable value in assessing inventory balances. Inventory costs include those costs directly attributable to products, including all manufacturing overhead but excluding costs to distribute. The inventories cost is recorded at standard cost, which approximates actual cost, on the first-in first-out basis (“FIFO”). During the fourth quarter of fiscal year 2022, the Company updated the process by which it estimates the value of its inventory. This included updating the assumptions that are used in determining and treating certain capitalized costs, primarily by incorporating the impacts of changes in the amount of recycled content introduced into the Company’s products since its last standard costing revaluation. Vendor Rebates Certain vendor rebates and incentives are earned by the Company only when specified levels of periodic purchases are achieved. These vendor rebates are recognized based on a systematic and rational allocation of the cash consideration offered in respect of each of the underlying transactions, provided the amounts are probable and reasonably estimable. The Company records the incentives as a reduction in the cost of inventory. The Company records such incentives during interim periods based on actual results achieved on a year-to-date basis and its expectation that purchase levels will be obtained to earn the rebate. Customer Rebates The Company offers rebates to customers based on total amounts purchased by each customer during each calendar year. The Company provides for the estimated cost of rebates at the time revenue is recognized based on rebate program rates and anticipated sales to each customer eligible for rebates and other available information. Management reviews and adjusts these estimates, if necessary, based on the differences between actual experience and historical estimates. Refer to Note 2 for additional information. Product Warranties The Company provides product assurance warranties of various lengths and terms to certain customers based on standard terms and conditions. The Company provides for the estimated cost of warranties at the time revenue is recognized based on management’s judgment, considering such factors as cost per claim, historical experience, anticipated rates of claims, and other available information. Management reviews and adjusts these estimates, if necessary, based on the differences between actual experience and historical estimates. Refer to Note 8 for additional information. Property, Plant and Equipment, Net Property, plant and equipment (“PP&E”) is recorded at cost, net of accumulated depreciation. Major additions and betterments are capitalized while repair and/or maintenance expenses are charged to operations when incurred. Construction in progress is also recorded at cost and includes capitalized interest, if material. Depreciation for financial reporting purposes is computed using the straight-line method over the following estimated useful lives of the assets: Land improvements 10 years Building and improvements 7 - 40 years Manufacturing equipment 1 - 15 years Office furniture and equipment 3 - 12 years Vehicles 5 years Computer equipment 3 - 7 years Leasehold improvements are recorded at cost and depreciated over the standard life of the type of asset or the remaining life of the lease, whichever is shorter. Equipment held under capital leases is stated at the lower of the fair value of the asset or the net present value of the future minimum lease payments at the inception of the lease. For equipment held under capital leases, depreciation is computed using the straight-line method over the shorter of the estimated useful lives of the leased assets or the related lease term and is included within depreciation expense. PP&E is evaluated for impairment at the asset group level. If a triggering event suggests that a potential impairment has occurred, recoverability of these assets is assessed by evaluating whether or not future estimated undiscounted net cash flows are less than the carrying amount of the assets. If the estimated cash flows are less than the carrying amount, the assets are written down to their fair value through an impairment loss recognized as a non-cash component of “Operating income (loss)” within the Consolidated Statements of Comprehensive Income. The Company did not record an impairment charge for the years ended September 30, 2023, 2022 and 2021. During the year ended September 30, 2023, 2022 and 2021, the Company recognized losses on disposal of fixed assets in the ordinary course of business of $ 0.2 million , $ 0.5 million and $ 1.0 million , respectively, the losses related to assets in the Residential segment. These losses are classified as “Loss on disposal of property, plant and equipment” in a separate caption within the Consolidated Statements of Comprehensive Income within “Operating income”. Leases Right-of-use (“ROU”) assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The discount rate used to calculate the present value represents our incremental borrowing rate and is calculated based on the treasury yield curve commensurate with the term of each lease, and a spread representative of our borrowing costs. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Leases may be classified as either operating leases or finance leases. We have made an accounting policy election to not include leases with an initial term of 12 months or less on the balance sheet. See Note 9—Leases for additional information. Goodwill The Company accounts for goodwill as the excess of the purchase price over the net amount of identifiable assets acquired and liabilities assumed in a business combination measured at fair value. The Company assigns goodwill to six reporting units based on which reporting unit is expected to benefit from the business combination as of the acquisition date. Goodwill is not subject to amortization; rather, the Company tests goodwill for impairment annually during the fourth fiscal quarter ended September 30 or more frequently if an event occurs or circumstances change in the interim that would more likely than not reduce the fair value of the asset below the carrying amount. The impairment evaluation may begin with a qualitative assessment of the factors that could impact the significant inputs used to estimate fair value to determine if it is more likely than not that the fair value of the reporting unit is less than its carrying amount or the Company may elect to bypass the qualitative assessment and proceed to a quantitative assessment to determine if goodwill is impaired. In quantitative impairment tests, if the estimated fair value of a reporting unit exceeds the carrying value, the Company considers that goodwill is not impaired. If the carrying value exceeds estimated fair value, there is an impairment of goodwill and an impairment loss is recorded. The Company calculates the impairment loss by comparing the fair value of the reporting unit less the carrying amount, including goodwill. Goodwill impairment would be limited to the carrying value of the goodwill. In performing the quantitative test, the Company measures the fair value of the reporting units to which goodwill is allocated using an income-based approach, a generally accepted valuation methodology, and relevant data available through the testing date. Under the income approach, fair value is determined using a discounted cash flow method, projecting future cash flows of each reporting unit, as well as a terminal value, and discounting such cash flows at a rate of return that reflects the relative risk of the cash flows. The key assumptions and factors used in this approach include, but are not limited to, revenue growth rates and profit margins based on internal Company forecasts, discount rates, perpetuity growth rates, future capital expenditures, and working capital requirements, among others, and a review of comparable market multiples for the industry segment as well as historical operating trends for the Company. The Company completed the annual goodwill impairment tests as of August 1, 2023, 2022 and 2021 , using a quantitative assessment for all six of the reporting units, a qualitative assessment for five reporting units and a quantitative assessment for one of the reporting units, and a qualitative assessment for three reporting units and a quantitative assessment for one of the reporting units, respectively. As a result of these respective annual assessments, the Company noted that the fair value of each reporting unit was determined to be in excess of the carrying value and as such, there were no impairment charges for the years ended September 30, 2023, 2022 and 2021 . Refer to Note 5 for additional information. Intangible Assets, Net Amortizable intangible assets include proprietary knowledge, trademarks, customer relationships and other intangible assets. The Company does not have any indefinite lived intangible assets other than goodwill. The intangible assets are being amortized on an accelerated basis using the sum of the years’ digits method over their estimated useful lives, which range from 3 to 20 years, reflecting the pattern in which the economic benefits are consumed or otherwise used up. The Company evaluates whether events or circumstances have occurred that warrant a revision to the remaining useful lives of intangible assets. In cases where a revision is deemed appropriate, the remaining carrying amounts of the intangible assets are amortized over the revised remaining useful lives. The Company evaluates amortizable intangible assets for potential impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be fully recoverable. If a triggering event suggests that a potential impairment has occurred, recoverability of these assets is assessed by evaluating the probability that future estimated undiscounted net cash flows will be less than the carrying amount of the long-lived assets. If the estimated cash flows are less than the carrying amount of the long-lived assets, the assets are written down to their fair value through an impairment loss recognized as a non-cash component of “Operating income (loss)”. The Company did not record an impairment charge for the years ended September 30, 2023, 2022 and 2021 . Refer to Note 5 for additional information. Deferred Financing Costs, Net The Company has recorded deferred financing costs incurred in conjunction with its debt obligations. The Company amortizes debt issuance costs over the remaining life of the related debt using the straight-line method for the Revolving Credit Facility and the effective interest method for other debt. Deferred financing costs, net of accumulated amortization, are presented as “Other assets” (non-current) in the Consolidated Balance Sheets, insofar as they relate to the Revolving Credit Facility. Deferred financing costs related to the 2022 Term Loan Agreement are recorded as a reduction of “Long-term debt – less current portion” in the Consolidated Balance Sheets. Refer to Note 7 for additional information. Stock-Based Compensation The Company determines the expense for all employee stock-based compensation awards by estimating their fair value and recognizing such value as an expense, on a straight-line, ratable or cliff basis, depending on the award, in the Consolidated Financial Statements over the requisite service period in which employees earn the awards. The Company estimates the fair value for service-based awards granted to employees using the Black Scholes pricing model. The fair value of performance-based awards that are expected to vest is recognized as compensation expense on a straight-line basis over the requisite service period. The fair value of service-based awards that are expected to vest is recognized as compensation expense on either (1) straight-line basis, (2) a ratable vesting basis or (3) a cliff vesting basis. The Company accounts for forfeitures as they occur. To determine the fair value of a stock-based award using Black Scholes models, the Company makes assumptions regarding the risk-free interest rate, expected future volatility, expected dividend yield and performance period. The risk-free rate is based on the U.S. treasury yield curve in effect at the time of grant. The Company estimates the expected volatility of the share price by reviewing the estimated post-IPO volatility levels of its common stock in conjunction with the historical volatility levels of public companies that operate in similar industries or are similar in terms of stage of development or size and then projecting this information toward its future expected volatility. The Company exercises judgment in selecting these companies, as well as in evaluating the available historical and implied volatility for these companies. Dividend yield is determined based on the Company’s future plans to pay dividends. The Company calculates the performance period based on the specific market condition to be achieved and derived from estimates of future performance. The Company calculates the expected term in years for each stock option using a simplified method based on the average of each option’s vesting term and original contractual term. The simplified method is used due to the lack of sufficient historical data available to provide a reasonable basis upon which to estimate the expected term of each stock option. Refer to Note 13 for additional information. Estimated Fair Value of Financial Instruments The carrying amounts for the Company’s financial instruments classified as current assets and liabilities, including cash and cash equivalents, trade accounts receivable and accrued expenses and accounts payable, approximate fair value due to their short maturities. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1—Quoted prices in active markets for identical assets or liabilities. Level 2—Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability . Refer to Note 10 for additional information. Derivatives The Company uses interest rate swap agreements to hedge its exposure to interest rate risk on its senior secured credit facilities. The Company designates derivatives that meet specific accounting criteria as qualifying hedges at inception. These criteria require the Company to have the expectation that the derivative will be highly effective at offsetting changes in the fair value or expected cash flows of the hedged exposure, both at inception of the hedging relationship and on an ongoing basis. The Company recognizes all derivative instruments at fair value and classifies them on the balance sheet as either Other current assets, Other assets, Accrued expenses and other liabilities or Other non-current liabilities. The interest rate swap agreements are designated as cash flow hedges. For cash flow hedges, the Company records the effective portion of the change in fair value of the derivative as part of Accumulated other comprehensive income and recognizes those changes in earnings in the period the hedged transaction affects earnings. The Company recognizes any ineffective portion of the change in the fair value of the derivative immediately in earnings. See Note 10 for additional information. Income Taxes Income taxes are provided on income reported for financial statement purposes, adjusted for permanent differences between financial statement reporting and income tax regulations. A valuation allowance is established whenever management believes that it is more likely than not that deferred tax assets may not be realizable. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the year in which the deferred tax assets or liabilities are expected to be realized or settled. The realization of the net deferred tax assets is primarily dependent on estimated future taxable income. A change in the Company’s estimate of future taxable income may require an increase or decrease in the valuation allowance. A liability for uncertain tax positions is recorded whenever management believes it is not more-likely than-not the position will be sustained on examination based solely on its technical merits. Interest and penalties related to underpayment of income taxes are classified as income tax expense. It is inherently difficult and subjective to estimate such amounts, as the Company has to determine the probability of various possible outcomes. The Company reevaluates these uncertain tax positions on a quarterly basis. This evaluation is based on factors including, but not limited to, changes in facts or circumstances, changes in tax law, effectively settled issues under audit, voluntary settlements and new audit activity. Such a change in recognition or measurement would result in the recognition of a tax benefit or an additional charge to the tax provision. Revision of Previously Filed Quarterly Reports During the fourth quarter of fiscal year 2023, the Company identified an error in its statement of cash flows related to classification of contingent consideration payments in connection with a recent acquisition. In the six and nine month periods ended March 31, 2023 and June 30, 2023, the Company classified such payments made more than three months from the date of the acquisition of $ 1.0 million and $ 5.8 million, respectively, within the operating activities section as opposed to within the financing activities section of the statement of cash flows. The Company evaluated the impact of the errors individually and in the aggregate on its previously issued financial statements, from both a qualitative and a quantitative perspective, and concluded that the errors were not material to any of the prior periods or to the current period financial statements. The Company determined that it will be appropriate to revise t

Revenue

Revenue	12 Months Ended
Revenue	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Revenue	2. REVENUE The Company sells its products to residential and commercial markets. The Company’s Residential segment principally generates revenue from the manufacture and sale of its premium, low-maintenance composite decking, railing, trim, moulding, pergolas and cabanas and accessories. The Company’s Commercial segment generates revenue from the sale of its partition and locker systems along with plastic sheeting and other non-fabricated products for special applications in industrial markets. The Company recognizes revenues when control of the promised goods is transferred to the Company’s customers in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods, at a point in time, when shipping occurs. Each product the Company transfers to the customer is considered one performance obligation. The Company has elected to account for shipping and handling costs as activities to fulfill the promise to transfer the goods. As a result of this accounting policy election, the Company does not consider shipping and handling activities as promised services to its customers. Customer contracts are typically fixed price and short-term in nature. The transaction price is based on the product specifications and is determined at the time of order. The Company may offer various sales incentive programs throughout the year. It estimates the amount of sales incentive to allocate to each performance obligation, or product shipped, using the most-likely-amount method of estimation, based on sales to the direct customer or sell-through customer. The estimate is updated each reporting period and any changes are allocated to the performance obligations on the same basis as at inception. Changes in estimate allocated to a previously satisfied performance obligation are recognized as part of net revenue in the period in which the change occurs under the cumulative catch-up method. In addition to sales incentive programs, the Company may offer a payment discount, if payments are received within thirty days. The Company estimates the payment discount that it believes will be taken by the customer based on prior history and using the most-likely-amount method of estimation. The Company believes the most-likely-amount method best predicts the amount of consideration to which it will be entitled. The payment discounts are also reflected as part of net revenue. The Company also engages in customer rebates, which are recorded in “Net sales” in the Consolidated Statements of Comprehensive Income and in “Accrued rebates” and “Trade receivables” in the Consolidated Balance Sheets. The Company recorded accrued rebates of $ 61.0 million , $ 50.5 million and $ 44.3 million as of September 30, 2023, 2022 and 2021, respectively, and contra trade receivables of $ 6.0 million , $ 6.1 million and $ 3.3 million as of September 30, 2023, 2022 and 2021 , respectively. The rebate activity was as follows (in thousands). As of September 30, 2023 2022 2021 Beginning balance $ 56,542 $ 47,648 $ 32,679 Rebate expense 106,762 88,057 76,763 Rebate payments ( 96,346 ) ( 79,163 ) ( 61,794 ) Ending balance $ 66,958 $ 56,542 $ 47,648 The Company records deferred revenue when cash payments are received or due in advance of the Company’s performance.

Inventories

Inventories	12 Months Ended
Inventories	Sep. 30, 2023
Inventory Disclosure [Abstract]
Inventories	. INVENTORIES Inventories are valued at the lower of cost or net realizable value, and are reduced for slow-moving and obsolete inventory. The inventories cost is recorded at standard cost, which approximates actual cost, on a first-in first-out (“FIFO”) basis. Inventories consisted of the following (in thousands): As of September 30, 2023 2022 Raw materials $ 67,330 $ 72,464 Work in process 37,038 39,829 Finished goods 116,733 187,612 Total inventories $ 221,101 $ 299,905 .

Property, Plant and Equipment -

Property, Plant and Equipment - Net	12 Months Ended
Property, Plant and Equipment - Net	Sep. 30, 2023
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment - Net	. PROPERTY, PLANT AND EQUIPMENT — NET Property, plant and equipment — net consisted of the following (in thousands): As of September 30, 2023 2022 Land and improvements $ 4,829 $ 3,350 Buildings and improvements 129,031 110,300 Manufacturing equipment 624,754 540,536 Computer equipment 32,300 28,198 Furnitures and fixtures 7,290 6,867 Vehicles 1,105 941 Total property, plant and equipment 799,309 690,192 Construction in progress 94,422 140,566 893,731 830,758 Accumulated depreciation ( 392,708 ) ( 312,845 ) Total property, plant and equipment – net $ 501,023 $ 517,913 Depreciation expense was approximately $ 81.2 million, $ 64.5 million and $ 50.6 million in the years ended September 30, 2023, 2022 and 2021, respectively. During the years ended September 30, 2023, 2022 and 2021 , $ 5.2 million, $ 5.6 million and $ 2.2 million of interest was capitalized, respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets - Net	12 Months Ended
Goodwill and Intangible Assets - Net	Sep. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets - Net	. GOODWILL AND INTANGIBLE ASSETS — NET Goodwill Goodwill consisted of the following (in thousands): Residential Commercial Total Goodwill before impairment as of September 30, 2022 $ 953,606 $ 72,589 $ 1,026,195 Accumulated impairment losses as of September 30, 2022 — ( 32,200 ) ( 32,200 ) Goodwill, net as of September 30, 2022 $ 953,606 $ 40,389 $ 993,995 Acquisitions 276 — 276 Goodwill before impairment as of September 30, 2023 $ 953,882 $ 72,589 $ 1,026,471 Accumulated impairment losses as of September 30, 2023 — ( 32,200 ) ( 32,200 ) Goodwill, net as of September 30, 2023 $ 953,882 $ 40,389 $ 994,271 Intangible assets, net The Company does no t have any indefinite lived intangible assets other than goodwill as of September 30, 2023 and 2022. Finite-lived intangible assets consisted of the following (in thousands): As of September 30, 2023 Lives in Gross Accumulated Net Propriety knowledge 10 — 15 $ 300,400 $ ( 253,608 ) $ 46,792 Trademarks 5 — 20 230,240 ( 164,759 ) 65,481 Customer relationships 12 — 19 176,852 ( 92,268 ) 84,584 Patents 9 — 10 8,500 ( 5,913 ) 2,587 Other intangible assets 3 — 15 4,076 ( 4,023 ) 53 Total intangible assets $ 720,068 $ ( 520,571 ) $ 199,497 As of September 30, 2022 Lives in Gross Accumulated Net Propriety knowledge 10 — 15 $ 300,400 $ ( 236,024 ) $ 64,376 Trademarks 5 — 20 230,240 ( 151,259 ) 78,981 Customer relationships 12 — 19 176,852 ( 78,015 ) 98,837 Patents 9 — 10 8,500 ( 4,950 ) 3,550 Other intangible assets 3 — 15 4,076 ( 3,985 ) 91 Total intangible assets $ 720,068 $ ( 474,233 ) $ 245,835 Amortization expense was approximately $ 46.3 million , $ 50.5 million and $ 49.8 million for the years September 30, 2023, 2022 and 2021, respectively. As of September 30, 2023 , the remaining weighted average amortization period for acquired intangible assets was 11.2 years. Amortization expense relating to these amortizable intangible assets as of September 30, 2023, is expected to be as follows (in thousands): 2024 $ 40,748 2025 35,204 2026 29,660 2027 24,115 2028 18,572 Thereafter 51,198 Total $ 199,497

Composition of Certain Balance

Composition of Certain Balance Sheet Accounts	12 Months Ended
Composition of Certain Balance Sheet Accounts	Sep. 30, 2023
Composition Of Certain Balance Sheet Accounts Disclosure [Abstract]
Composition of Certain Balance Sheet Accounts	. COMPOSITION OF CERTAIN BALANCE SHEET ACCOUNTS Allowance for Losses Allowance for losses consisted of the following (in thousands): As of September 30, 2023 2022 2021 Beginning balance $ 1,397 $ 1,109 $ 1,332 Provision 731 290 342 Bad debt write-offs ( 355 ) ( 2 ) ( 565 ) Ending balance $ 1,773 $ 1,397 $ 1,109 Accrued Expenses and Other Liabilities Accrued expenses consisted of the following (in thousands): As of September 30, 2023 2022 Employee related liabilities $ 34,313 $ 36,866 Taxes 6,959 142 Lease liability operating 4,180 5,223 Customer deposits 4,152 2,494 Marketing 3,868 4,272 Construction in progress 2,863 9,032 Lease liability finance 2,777 2,366 Warranty 2,739 2,900 Utilities 2,141 794 Professional fees 2,073 2,089 Freight 1,242 1,821 Commissions 991 1,032 Other 3,696 3,558 Total accrued expenses and other current liabilities $ 71,994 $ 72,589

Debt

Debt	12 Months Ended
Debt	Sep. 30, 2023
Debt Disclosure [Abstract]
Debt	. DEBT Debt consisted of the following (in thousands): As of September 30, 2023 2022 2022 Term Loan due April 28, 2029 — SOFR + 2.50 % + 0.1% ( 7.92 % at September 30, 2023 and 4.09 % at September 30, 2022) $ 594,000 $ 600,000 Revolving Credit Facility through March 31, 2026 - SOFR + 0.1 % — — Total 594,000 600,000 Less unamortized deferred financing fees ( 3,996 ) ( 4,712 ) Less unamortized original issue discount ( 3,739 ) ( 4,409 ) Less current portion ( 6,000 ) ( 6,000 ) Long-term debt — less current portion and unamortized $ 580,265 $ 584,879 As of September 30, 2023, the Company scheduled fiscal year debt payment on the 2022 Term Loan Agreement as follows (in thousands): 2024 $ 6,000 2025 6,000 2026 6,000 2027 6,000 2028 6,000 Thereafter 564,000 Total $ 594,000 Term Loan Agreements The term loan agreement, as amended and restated from time to time (the “Term Loan Agreement”), was a first lien term loan originally entered into on September 30, 2013 by the Company’s wholly-owned subsidiary, The AZEK Group LLC (as successor-in-interest to CPG Merger Sub LLC), as the initial borrower with a syndicate of lenders party thereto. On April 28, 2022, the obligations under the Term Loan Agreement were paid off in full and the Term Loan Agreement was terminated. On April 28, 2022, The AZEK Group LLC entered into a new $ 600.0 million first lien term loan credit agreement (the “2022 Term Loan Agreement”), the proceeds of which were applied, among other uses, to prepay the obligations of the Term Loan Agreement in full. The 2022 Term Loan Agreement is a first lien term loan and will mature on April 28, 2029 , subject to acceleration or prepayment. The 2022 Term Loan Agreement will amortize in equal quarterly installments of 0.25 % of the aggregate principal amount of the loans outstanding, subject to reduction for certain prepayments. The loans thereunder bear an interest rate equal to (i) in the case of ABR borrowings, the highest of (a) the Federal Funds Rate plus 0.50 %, (b) the Prime Rate as in effect on such day and (c) the one-month Term Secured Overnight Financing Rate ("SOFR") plus 1.00 % per annum, provided that in no event will the alternative base rate be less than 1.50 % per annum, plus an applicable margin of 1.50 % and (ii) in the case of SOFR borrowings, the Term SOFR rate for the applicable interest period, in each case, plus an applicable margin of 2.50 %. As of September 30, 2023 and 2022 , The AZEK Group LLC had $ 594.0 million and $ 600.0 million outstanding under the 2022 Term Loan Agreement. The obligations under the 2022 Term Loan Agreement are secured by a first priority security interest in the membership interests of The AZEK Group LLC owned by the Company, the equity interests of The AZEK Group LLC’s domestic subsidiaries, other than certain immaterial subsidiaries and other excluded subsidiaries, and all remaining assets not constituting Revolver Priority Collateral (as defined below and subject to certain exceptions) of the Company, The AZEK Group LLC and the subsidiaries of The AZEK Group LLC that are guarantors under the 2022 Term Loan Agreement (the “Term Loan Priority Collateral”), and a second priority security interest in the Revolver Priority Collateral. The obligations under the 2022 Term Loan Agreement are guaranteed by the Company and the wholly owned domestic subsidiaries of The AZEK Group LLC other than certain immaterial subsidiaries and other excluded subsidiaries. Loans under the 2022 Term Loan Agreement may be voluntarily prepaid in whole, or in part, in each case without premium or penalty, subject to certain customary conditions. The 2022 Term Loan Agreement also requires mandatory prepayments of loans under the 2022 Term Loan Agreement from the proceeds of certain debt issuances and certain asset dispositions (subject to certain reinvestment rights) and, commencing with the fiscal year ended September 30, 2023, a percentage of excess cash flow (subject to step-downs upon The AZEK Group LLC achieving certain leverage ratios and other reductions in connection with other debt prepayments). The 2022 Term Loan Agreement contains affirmative covenants, negative covenants and events of default, which are broadly consistent with those in the Revolving Credit Facility (with certain differences consistent with the differences between a revolving loan and term loan) and that are customary for facilities of this type. The 2022 Term Loan Agreement does not have any financial maintenance covenants. The 2022 Term Loan Agreement also includes customary events of default, including the occurrence of a change of control. In connection with the April 28, 2022 refinancing, the Company recognized $ 5.1 million in interest expense in the year ended September 30, 2022, of which $ 0.5 million is related to the write-off of unamortized debt discount and debt issuance costs and $ 4.6 million is related to third-party costs of debt modification. The Company incurred $ 4.5 million in lender fees which, together with $ 1.8 million in remaining unamortized debt discount and debt issuance costs and $ 3.4 million in third-party costs for new lenders, have been recorded as a reduction of long-term debt and are being amortized over the remaining contractual life of the 2022 Term Loan Agreement using the effective interest method. As of September 30, 2023 and 2022 , unamortized deferred financing fees related to the 2022 Term Loan Agreement were $ 4.0 million and $ 4.7 million. Revolving Credit Facility The AZEK Group LLC has also entered into a revolving credit facility, as amended and restated from time to time (the “Revolving Credit Facility”), with certain of our direct and indirect subsidiaries and certain lenders party thereto. The Revolving Credit Facility provides for maximum aggregate borrowings of up to $ 150.0 million, subject to an asset-based borrowing base. The borrowing base is limited to a set percentage of eligible accounts receivable and inventory, less reserves that may be established by the administrative agent and the collateral agent in the exercise of their reasonable credit judgment. The AZEK Group LLC had no outstanding borrowings under the Revolving Credit Facility as of September 30, 2023 and September 30, 2022 . In addition, The AZEK Group LLC had $ 2.8 million of outstanding letters of credit held against the Revolving Credit Facility as of both September 30, 2023 and September 30, 2022 . The AZEK Group LLC had approximately $ 147.2 million available under the borrowing base for future borrowings as of September 30, 2023 . The AZEK Group LLC also has the option to increase the commitments under the Revolving Credit Facility by up to $ 100.0 million, subject to certain conditions. On March 31, 2021, The AZEK Group LLC amended the Revolving Credit Facility, resulting in a repricing and extension thereof. Pursuant to such amendment, the interest rate has been reduced by 25 basis points to (i) for ABR borrowings, the highest of (a) the Federal Funds Rate plus 50 basis points , (b) the prime rate and (c) the LIBOR as of such date for a deposit in U.S. dollars with a maturity of one month plus 100 basis points, plus, in each case, a spread of 25 to 75 basis points , based on average historical availability , or (ii) for Eurocurrency borrowings, adjusted LIBOR plus a spread of 125 to 175 basis points , based on average historical availability . The maturity date for the Revolving Credit Facility was extended from May 9, 2022 to the earlier of March 31, 2026 and the date that is 91 days prior to the maturity of the Term Loan Agreement or any permitted refinancing thereof. In connection with the March 31, 2021 amendment, the Company recognized $ 0.1 million in interest expense in the year ended September 30, 2021 related to the write-off of unamortized debt issuance costs. The Company incurred $ 0.9 million in lender and third-party fees which, together with $ 0.5 million in remaining unamortized debt issuance costs, have been recorded as other assets and are being amortized over the remaining contractual life of the facility on a straight-line basis. Deferred financing costs, net of accumulated amortization, related to the Revolving Credit Facility at September 30, 2023 and September 30, 2022 were $ 0.7 million and $ 0.9 million, respectively. On January 26, 2023, The AZEK Group LLC further amended the Revolving Credit Facility, replacing all LIBOR-based provisions with provisions reflecting SOFR, including, without limitation, the use of a new Adjusted Term SOFR benchmark rate equal to Term SOFR (as defined in the Revolving Credit Agreement) plus 0.10 %. A “commitment fee” accrues on any unused portion of the commitments under the Revolving Credit Facility during the preceding three calendar month period. If the average daily used percentage is greater than 50%, the commitment fee equals 25 basis points, and if the average daily used percentage is less than or equal to 50%, the commitment fee equals 37.5 basis points. The commitment fees were $ 0.6 million, $ 0.5 million and $ 0.6 million for the years ended September 30, 2023, 2022 and 2021, respectively. The obligations under the Revolving Credit Facility are guaranteed by the Company and its wholly owned domestic subsidiaries other than certain immaterial subsidiaries and other excluded subsidiaries. The obligations under the Revolving Credit Facility are secured by a first priority security interest in substantially all of the accounts receivable, inventory, deposit accounts, securities accounts and cash assets of the Company, The AZEK Group LLC and the subsidiaries of The AZEK Group LLC that are guarantors under the Revolving Credit Facility, and the proceeds thereof (subject to certain exceptions) (the “Revolver Priority Collateral”), plus a second priority security interest in all of the Term Loan Priority Collateral. The Revolving Credit Facility may be voluntarily prepaid in whole, or in part, in each case without premium or penalty. The AZEK Group LLC is also required to make mandatory prepayments (i) when aggregate borrowings exceed commitments or the applicable borrowing base and (ii) during “cash dominion,” which occurs if (a) the availability under the Revolving Credit Facility is less than the greater of (i) $12.5 million and (ii) 10% of the lesser of (x) $150.0 million and (y) the borrowing base, for five consecutive business days or (b) certain events of default have occurred and are continuing. The Revolving Credit Facility contains affirmative covenants that are customary for financings of this type, including allowing the Revolver Administrative Agent to perform periodic field exams and appraisals to evaluate the borrowing base. The Revolving Credit Facility contains various negative covenants, including limitations on, subject to certain exceptions, the incurrence of indebtedness, the incurrence of liens, dispositions, investments, acquisitions, restricted payments, transactions with affiliates, as well as other negative covenants customary for financings of this type. The Revolving Credit Facility also includes a financial maintenance covenant, applicable only when the excess availability is less than the greater of (i) 10% of the lesser of the aggregate commitments under the Revolving Credit Facility and the borrowing base, and (ii) $12.5 million . In such circumstances, The AZEK Group LLC would be required to maintain a minimum fixed charge coverage ratio (as defined in the Revolving Credit Facility) for the trailing four quarters equal to at least 1.0 to 1.0 ; subject to The AZEK Group LLC’s ability to make an equity cure (no more than twice in any four quarter period and up to five times over the life of the facility). As of September 30, 2023, The AZEK Group LLC was in compliance with the financial and nonfinancial covenants imposed by the Revolving Credit Facility. The Revolving Credit Facility also includes customary events of default, including the occurrence of a change of control. Interest expense consisted of the following (in thousands): Years Ended September 30, 2023 2022 2021 Interest expense 2022 Term Loan Agreement $ 41,936 $ 10,640 $ — Term Loan Agreement — 8,824 17,826 Revolving Credit Facility 718 838 629 Other 4,484 3,661 828 Amortization Debt issue costs 2022 Term Loan Agreement 716 4,892 — Term Loan Agreement — 1,056 2,497 Revolving Credit Facility 262 262 495 Original issue discounts 2022 Term Loan Agreement 670 279 — Term Loan Agreement — 126 193 Less capitalized interest ( 5,211 ) ( 5,622 ) ( 2,157 ) Interest expense 43,575 24,956 20,311 Less interest income ( 4,282 ) — — Interest expense, net $ 39,293 $ 24,956 $ 20,311 Refer to Note 10 for information pertaining to the fair value of the Company’s debt as of September 30, 2023 and 2022 .

Product Warranties

Product Warranties	12 Months Ended
Product Warranties	Sep. 30, 2023
Product Warranties Disclosures [Abstract]
Product Warranties	. PRODUCT WARRANTIES The Company provides product assurance warranties of various lengths ranging from 5 years to lifetime for limited coverage for a variety of material and workmanship defects based on standard terms and conditions between the Company and its customers. Warranty coverage depends on the product involved. The warranty reserve activity was as follows (in thousands): As of September 30, 2023 2022 Beginning balance $ 15,023 $ 12,699 Adjustments to reserve 3,657 5,030 Warranty claims payment ( 2,485 ) ( 2,706 ) Ending balance 16,195 15,023 Current portion of accrued warranty ( 2,739 ) ( 2,900 ) Accrued warranty — less current portion $ 13,456 $ 12,123

Leases

Leases	12 Months Ended
Leases	Sep. 30, 2023
Leases [Abstract]
Leases	. LEASES On October 1, 2020, the Company adopted ASU 2016-02, "Leases (Topic 842)," and the related amendments (collectively "ASC 842"). The Company leases vehicles, machinery, manufacturing facilities, office space, land, and equipment under both operating and finance leases. We sublease excess office real estate to a third-party tenant. The Company determines if an arrangement is a lease at inception. A contract is or contains a lease if the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration. As of both September 30, 2023 and 2022, amounts associated with leases are included in Other assets, Accrued expense and other liabilities and Other non-current liabilities in our consolidated balance sheet. For leases with initial terms greater than 12 months, the Company considers these right-of-use assets and records the related asset and obligation at the present value of lease payments over the term. For leases with initial terms equal to or less than 12 months, we do not consider them as right-of-use assets and instead consider them short-term lease costs that are recognized on a straight-line basis over the lease term. Our leases may include escalation clauses, renewal options and/or termination options that are factored into our determination of lease term and lease payments when its reasonably certain the option will be exercised. Renewal options range from 1 year to 20 years. The options to extend or terminate a lease are at our discretion. We have elected to take the practical expedient and not separate lease and non-lease components of contracts. We estimate our incremental borrowing rate to discount the lease payments based on information available at lease commencement because the implicit rate of the lease is generally not known. Our lease agreements do not contain any material residual value guarantees. Lease assets and lease liabilities as of September 30, 2023 and 2022 were as follows: As of September 30, Leases Classification on Balance Sheet 2023 2022 Assets ROU operating lease assets Other assets $ 15,423 $ 19,724 Finance lease assets Other assets 71,529 73,541 Total lease assets $ 86,952 $ 93,265 Liabilities Current Operating Accrued expenses and other liabilities $ 4,180 $ 5,223 Finance Accrued expenses and other liabilities 2,777 2,366 Non-Current Operating Other non-current liabilities 13,699 17,261 Finance Other non-current liabilities 75,718 75,706 Total lease liabilities $ 96,374 $ 100,556 The components of lease expense for the years ended September 30, 2023, 2022 and 2021 were as follows: Years Ended September 30, (in thousands) 2023 2022 2021 Operating lease expense $ 5,920 $ 5,669 $ 4,007 Finance lease amortization of assets 5,053 3,477 1,191 Finance lease interest on lease liabilities 4,391 3,616 827 Short term 392 574 133 Sublease income ( 293 ) ( 347 ) ( 428 ) Total lease expense $ 15,463 $ 12,989 $ 5,730 Cash flows related to leases for the years ended September 30, 2023, 2022 and 2021 were as follows: Years Ended September 30, 2023 2022 2021 Cash paid for amounts included in the measurement of lease liabilities: Operating leases - Operating cash flows $ 6,171 $ 5,973 $ 4,096 Finance leases - Operating cash flows 4,391 3,617 827 Finance leases - Financing cash flows 2,619 249 1,921 Leased assets obtained in exchange for operating lease liabilities 3,041 5,487 10,239 Leased assets obtained in exchange for finance lease liabilities 789 27,438 47,578 The table below present supplemental information related to leases as of September 30, 2023 and 2022: As of September 30, 2023 2022 Weighted-average remaining lease term (years) Operating leases 6.8 6.9 Finance leases 25.4 26.5 Weighted-average discount rate Operating leases 4.4 % 4.1 % Finance leases 5.8 % 5.9 % Maturities of Lease Liabilities The table below reconciles the undiscounted cash flows for each of the first five years and the total of the remaining years to the finance lease liabilities and operating lease liabilities recorded on the balance sheet as of September 30, 2023: As of September 30, 2023 (in thousands) Operating Leases Finance Leases Total 2024 $ 4,856 $ 7,101 $ 11,957 2025 3,919 6,998 10,917 2026 2,594 6,835 9,429 2027 1,906 6,368 8,274 2028 1,642 5,265 6,907 Thereafter 6,070 117,013 123,083 Total lease payments 20,987 149,580 170,567 Less: Interest ( 3,108 ) ( 71,085 ) ( 74,193 ) Present Value of lease liability $ 17,879 $ 78,495 $ 96,374

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
Fair Value of Financial Instruments	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	10. FAIR VALUE OF FINANCIAL INSTRUMENTS The Company measures and records in its consolidated financial statements certain assets and liabilities at fair value. ASC Topic 820, Fair Value Measurement and Disclosures , establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). This hierarchy consists of the following three levels: • Level 1—Assets and liabilities whose values are based on unadjusted quoted prices for identical assets or liabilities in an active market. • Level 2—Assets and liabilities whose values are based on inputs other than those included in Level 1, including quoted market prices in markets that are not active; quoted prices of assets or liabilities with similar attributes in active markets; or valuation models whose inputs are observable or unobservable but corroborated by market data. • Level 3—Assets and liabilities whose values are based on valuation models or pricing techniques that utilize unobservable inputs that are significant to the overall fair value measurement. Certain assets are measured at fair value on a nonrecurring basis; that is, the instruments are not measured at fair value on an ongoing basis, but are subject to fair value adjustments in certain circumstances (for example, when there is evidence of impairment). Financial instruments with a fair value that approximates carrying value— The carrying amounts of cash and cash equivalents, trade receivables and payables, as well as financial instruments included in other current assets and other current liabilities, approximate fair values because of their short-term maturities. Financial instruments with a fair value different from carrying value— The Company has, where appropriate, estimated the fair value of financial instruments for which the amortized cost carrying value may be significantly different than the fair value. As of September 30, 2023 and 2022 , these instruments include outstanding debt. As described in Note 7 Debt, the Company records debt at amortized cost. The carrying values and the estimated fair values of the debt financial instruments (Level 2 measurements) consisted of the following (in thousands): As of September 30, 2023 2022 Principle Outstanding Estimated Principle Outstanding Estimated 2022 Term Loan Agreement due April 28, 2029 $ 594,000 $ 595,485 $ 600,000 $ 586,500 The fair values of the debt instrument were determined using trading prices between qualified institutional buyers; therefore, are classified as Level 2. Financial instruments remeasure at fair value on a recurring basis – During the year ended September 30, 2022, the Company entered into an arrangement for a contingent payment to the former owner and employee of StruXure. The contingent payment is based on achievement of a minimum EBITDA amount and a multiple of EBITDA, for EBITDA exceeding a higher threshold for calendar year 2022. Based on the formula, the potential contingent payout can range from zero to $ 13.9 million. At the date of acquisition, the fair value was estimated to be $ 9.5 million. As of March 31, 2023, the fair value was increased to $ 12.7 million based on the actual EBITDA amount for StruXure. Compensation expense of $ 9.5 million was recognized for the year ended September 30, 2022 and $ 3.2 million was recognized for the year ended September 30, 2023. The Company paid $ 12.7 million as settlement of the contingent liability in April, 2023. In connection with the acquisition of INTEX on August 1, 2022 , the Company entered into a contingent consideration arrangement with the former owner of INTEX. The contingent consideration is based on achievement of a minimum gross profit amount for calendar year 2022. Based on the formula, the potential contingent consideration can range from zero to $ 6.2 million. At the date of acquisition, the fair value was estimated to be $ 5.8 million. As of December 31, 2022, the fair value was increased to $ 6.2 million. Contingent payment of $ 5.8 million was included in the acquisition purchase price at the date of acquisition and the change in fair value of $ 0.4 million was recognized in selling, general and administrative expense for the year ended September 30, 2023. The Company paid $ 6.2 million as settlement of the contingent liability in fiscal year 2023. Derivative Instruments - The Company’s objective in using interest rate derivative instruments is to hedge against interest rate volatility associated with its senior secured credit facilities by converting a portion of its floating rate debt to fixed rate debt. In November 2022, the Company entered into two interest rate swap agreements with Barclays Bank PLC (“Barclays”) to manage interest rate risk related to 2022 Term Loan. Each agreement has a notional amount of $ 150 million and will expire on October 31, 2025 . One agreement swaps variable interest at a rate based on SOFR with a fixed rate of 4.39 % and the second with a fixed rate of 4.48 %. At the inceptions of the swap agreements and as of September 30, 2023, both swaps were designated and qualified as cash flow hedges in accordance with ASC 815. Their gain (loss) is recorded in Accumulated other comprehensive income (loss) and then reclassified into Interest expense in the same period in which the hedged transaction affects earnings. As of September 30, 2023 , the Company expects to reclass approximately $ 2.6 million ($ 1.9 million after-tax) as a reduction to interest expense in the next 12 months. The following table provides the fair values of the interest rate derivative instruments as well as their classification on the Balance Sheet as of September 30, 2023 and 2022 (in thousands): Fair Value as of Fair Value Hierarchy Balance Sheet Location September 30, 2023 September 30, 2022 Assets Interest rate swaps Level 2 Other current assets $ 2,558 $ — Liabilities Interest rate swaps Level 2 Other non-current liabilities $ 65 $ — The Company estimates the fair value of interest rate swaps using a valuation model based on observable market data, such as yield curves. Both swaps are classified as Level 2 measurement in the fair value hierarchy. The following table summarizes the effects of the interest rate derivative instruments on Accumulated other comprehensive income (loss) as of September 30, 2023 (in thousands): Before-tax Amount Income Tax Expense Net of Tax Amount Balance - September 30, 2022 $ — $ — $ — Amount of gain recognized in other comprehensive income 3,474 870 2,604 Amount of gain reclassified from accumulated other comprehensive income (loss) into net income ( 981 ) ( 255 ) ( 726 ) Balance - September 30, 2023 $ 2,493 $ 615 $ 1,878 The Company recognizes the reclassification of gain from Accumulated other comprehensive income (loss) to Net income in Interest expense, net within the Consolidated Statements of Comprehensive Income.

Segments

Segments	12 Months Ended
Segments	Sep. 30, 2023
Segment Reporting [Abstract]
Segments	11. SEGMENTS Operating segments for the Company are determined based on information used by the chief operating decision maker (“CODM”) in deciding how to evaluate performance and allocate resources to each of the segments. The CODM reviews Adjusted EBITDA and Adjusted EBITDA Margin as the key segment measures of performance. Adjusted EBITDA is defined as segment operating income (loss) plus depreciation and amortization, adjusted by adding thereto or subtracting therefrom stock-based compensation costs, business transformation costs, acquisition costs, capital structure transaction costs, and certain other costs. Adjusted EBITDA Margin is defined as Adjusted EBITDA divided by net sales. The Company has two reportable segments, Residential and Commercial. The reportable segments were determined primarily based on products and end markets as follows: • Residential—The Residential segment manufactures and distributes decking, railing, trim, moulding, pergolas and cabanas and accessories through a national network of dealers and distributors and multiple home improvement retailers providing extensive geographic coverage and enabling the Company to effectively serve contractors. The addition of StruXure provides high-quality and innovative aluminum pergolas and cabanas that is complementary to TimberTech portfolio. The addition of INTEX strengthens the existing Railing and Exteriors portfolios. This segment is impacted by trends in and the strength of home repair and remodel activity. • Commercial—The Commercial segment manufactures, fabricates and distributes resin based extruded sheeting products for a variety of commercial and industrial applications through a widespread distribution network as well as directly to original equipment manufacturers. This segment includes Scranton Products which manufactures lockers and partitions and Vycom which manufactures resin based sheeting products. This segment is impacted by trends in and the strength of the new construction sector. The accounting policies of the operating segments are the same as those described in Note 1, “Summary of Significant Accounting Policies”. Intercompany transactions between segments are excluded as they are not included in management’s performance review of the segments. Currently foreign revenue accounts for less than 10% of consolidated revenue. The Company does not disclose assets outside of the United States as they totaled less than 10% of the consolidated assets as of September 30, 2023, 2022 and 2021. The segment data below includes data for Residential and Commercial for the years ended and as of September 30, 2023, 2022 and 2021 (in thousands). Years Ended and As of September 30, Residential Commercial Corporate and Total 2023 2022 2021 2023 2022 2021 2023 2022 2021 2023 2022 2021 Net Sales $ 1,222,866 $ 1,168,751 $ 1,044,126 $ 147,450 $ 186,835 $ 134,848 $ — $ — $ — $ 1,370,316 $ 1,355,586 $ 1,178,974 Adjusted EBITDA 329,853 323,377 314,563 31,008 40,255 19,323 ( 69,638 ) ( 62,592 ) ( 59,699 ) 291,223 301,040 274,187 Capital Expenditures 81,592 162,739 169,490 4,321 5,645 3,473 2,632 2,554 2,156 88,545 170,938 175,119 Depreciation and 119,466 105,421 88,732 8,789 9,332 9,127 4,289 3,780 3,745 132,544 118,533 101,604 Goodwill 953,882 953,606 911,001 40,389 40,389 40,389 — — — 994,271 993,995 951,390 Total Assets 2,150,994 2,173,069 1,953,126 192,865 186,824 200,277 21,695 23,198 34,431 2,365,554 2,383,091 2,187,834 Years Ended September 30, 2023 2022 2021 Segment Adjusted EBITDA Residential $ 329,853 $ 323,377 $ 314,563 Commercial 31,008 40,255 19,323 Total Adjusted EBITDA for reporting segments $ 360,861 $ 363,632 $ 333,886 Unallocated net expenses ( 69,638 ) ( 62,592 ) ( 59,699 ) Adjustments to income (loss) before income tax provision Depreciation and amortization ( 132,544 ) ( 118,533 ) ( 101,604 ) Stock-based compensation costs ( 18,704 ) ( 18,105 ) ( 22,670 ) Acquisition and divestiture costs (1) ( 6,890 ) ( 13,406 ) — Secondary offering costs ( 1,065 ) — ( 2,592 ) Inventories (2) — ( 19,297 ) — Other costs (3) ( 843 ) ( 2,764 ) ( 5,192 ) Interest expense, net ( 39,293 ) ( 24,956 ) ( 20,311 ) Income (loss) before income taxes $ 91,884 $ 103,979 $ 121,818 (1) Acquisition and divestiture costs reflect costs directly related to completed acquisitions of $ 3.9 million and $ 11.5 million for fiscal years 2023 and 2022, respectively, costs related to divestiture of $ 3.0 million and $ 0.5 million for fiscal year 2023 and 2022, respectively, and inventory step-up adjustments related to recording the inventory of acquired businesses at fair value on the date of acquisition of $ 1.4 million for fiscal years 2022. (2) During the fourth quarter of fiscal year 2022, the Company updated the process by which it estimates the value of its inventory. This included updating the assumptions that are used in determining and treating certain capitalized costs, primarily by incorporating the impacts of changes in the amount of recycled content introduced into its products. (3) Other costs reflect reduction in workforce costs of $ 0.5 million and $ 1.6 million for fiscal years 2023 and 2022, respectively, costs for legal expenses of $ 0.3 million, $ 0.9 million and $ 2.3 million for fiscal years 2023, 2022 and 2021, respectively, other costs of $ 0.2 million for fiscal year 2022, costs related to an incentive plan and other ancillary expenses associated with the initial public offering of $ 0.1 million and $ 2.4 million for fiscal years 2022 and 2021, respectively, and impact of the retroactive adoption of ASC 842 leases of $ 0.5 million for fiscal year 2021.

Capital Stock

Capital Stock	12 Months Ended
Capital Stock	Sep. 30, 2023
Stockholders' Equity Note [Abstract]
Capital Stock	12. CAPITAL STOCK Secondary Offerings On January 26, 2021, the Company completed an offering of 23,000,000 shares of Class A common stock, par value $ 0.001 per share, including the exercise in full by the underwriters of their option to purchase up to 3,000,000 additional shares of Class A common stock, at a public offering price of $ 40.00 per share. The shares were sold by certain of the Selling Stockholders. The Company did not receive any of the proceeds from the sale of the shares by those Selling Stockholders. In connection with the offering, the Company incurred approximately $ 1.2 million in expenses. On June 1, 2021, the Company completed an offering of 17,250,000 shares of Class A common stock, par value $ 0.001 per share, including the exercise in full by the underwriters of their option to purchase up to 2,250,000 additional shares of Class A common stock, at a public offering price of $ 43.50 per share. The shares were sold by certain of the Selling Stockholders. The Company did not receive any of the proceeds from the sale of the shares by those Selling Stockholders. In connection with the offering, the Company incurred approximately $ 1.1 million in expenses. During the three months ended June 30, 2023, the Company completed an offering of 16,100,000 shares of Class A common stock, par value $ 0.001 per share, including the exercise in full by the underwriter of its option to purchase up to 2,100,000 additional shares of Class A common stock. All of the shares were sold by the Selling Stockholders to the underwriter at a price of $ 24.36 per share which the underwriter was then permitted to sell at variable prices to the public. The Company did not receive any of the proceeds from the sale of the shares by those Selling Stockholders. In connection with the secondary offering, the Company incurred approximately $ 1.1 million in expenses. In connection with the secondary offering, the Company purchased from the underwriter 1,477,832 shares of its Class A common stock that were sold by the Selling Stockholders to the underwriter at a price per share of $ 24.36 , which is equal to the price paid by the underwriter to the Selling Stockholders, resulting in an aggregate purchase price of approximately $ 36.0 million. The repurchase was made pursuant to the Company’s Share Repurchase Program (as defined below). Share Repurchase Program On May 5, 2022, the Board of Directors authorized the Company to repurchase up to $ 400 million of the Company’s Class A common stock (the “Share Repurchase Program”). The Share Repurchase Program allows the Company to repurchase its shares opportunistically from time to time. Purchases may be effected through one or more open market transactions, privately negotiated transactions, transactions structured through investment banking institutions, accelerated share repurchases or tender offers, some of which may be effected through Rule 10b5-1 plans, or a combination of the foregoing. The timing of repurchases will depend upon several factors, including market and business conditions, and repurchases may be discontinued at any time. The table below summaries the Company's repurchases of its Class A common stock during the year ended September 30, 2023 and 2022 (in thousands, except per share amount): Year Ended September 30, 2023 2022 Total number of shares repurchased 4,152 4,117 Reacquisition cost (1), (2), (3) $ 116,579 $ 81,483 Average price per share $ 28.08 $ 19.79 (1) Reacquisition cost in the year ended September 30, 2023 includes the $ 36.0 million repurchase from the underwriter upon the completion of the secondary offering. The remaining repurchases in the year ended September 30, 2023 were made through open market transactions. (2) On August 16, 2022, the U.S. government enacted the Inflation Reduction Act of 2022 (the “Inflation Reduction Act”), that includes, among other provisions, a one percent excise tax on net repurchases of stock after December 31, 2022. As of September 30, 2023 , the Company recognized $ 1.1 million excise tax as reacquisition cost of share repurchases. (3) During the year ended September 30, 2022 , the Company repurchased $ 50.0 million of shares under an accelerated share repurchase agreement ("ASR") and $ 31.5 million of shares on the open market. As of September 30, 2023 , the Company had approximately $ 201.9 million available for repurchases under the Share Repurchase Program. At September 30, 2023 , the following amounts were issued and outstanding: 147,699,313 shares of Class A common stock and 100 shares of Class B common stock. The Company has not issued any shares of preferred stock.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
Stock-Based Compensation	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	13. STOCK-BASED COMPENSATION The Company grants stock-based awards to attract, retain and motivate key employees and directors. The 2020 Omnibus Incentive Compensation Plan (“2020 Plan”), provides for the grant of stock options, stock appreciation rights, restricted stock, restricted stock units, dividend equivalent rights, and performance-based or other equity-related awards to the Company’s employees and directors. The maximum aggregate number of shares that may be issued under the 2020 Plan is 15,852,319 shares with 2,759,532 shares remaining in the reserve. The total aggregate number of shares may be adjusted as determined by the Board of Directors. On February 4, 2021, the Compensation Committee of the Board of Directors authorized certain changes to our Chief Financial Officer’s (“CFO”) stock-based awards which are expected to be effective in connection with his retirement and contingent on the successful transition to his successor. These changes contemplate a retirement eligibility provision which is expected to allow certain awards to continue to vest in due course following retirement and extend the exercisability of the outstanding and exercisable stock options to the end of the contractual term of the options. This resulted in a Type III Modification (improbable to probable) as defined in accounting guidance, accounted for as a cancellation of the original award and a new grant under the revised terms, resulting in $ 8.8 million of share-based compensation expense in the fiscal year 2021. Stock-based compensation expense for the years ended September 30, 2023, 2022 and 2021 was $ 18.7 million, $ 18.1 million and $ 22.7 million, respectively, recognized in “Selling, general and administrative expenses” in the Consolidated Statements of Comprehensive Income. Total income tax benefit for the years ended September 30, 2023, 2022 and 2021 was $ 3.6 million, $ 4.1 million and $ 3.8 million, respectively. As of September 30, 2023 , the Company had not yet recognized compensation cost on unvested stock-based awards of $ 23.5 million, with a weighted average remaining recognition period of 1.6 years. The Company uses the Black Scholes pricing model to estimate the fair value of its service-based option awards as of the grant date. Under the terms of the 2020 Plan, all stock options will expire if not exercised within ten years of the grant date. The fair value of each restricted stock unit award is based on the closing price on the date of grant. The following table sets forth the significant assumptions used for the service-based awards granted during the years ended September 30: 2023 2022 2021 Weighted average grant date fair value $ 9.02 $ 16.98 $ 12.49 Risk-free interest rate 3.77 % 1.34 % 0.56 %- 0.81 % Expected volatility 40.00 % 40.00 % 35.00 % Expected term (in years) 6.00 6.00 6.00 Expected dividend yield 0.00 % 0.00 % 0.00 % Stock Options The following table summarizes the performance-based stock option activity for the year ended September 30, 2023: Number of Weighted Weighted Aggregate (in years) (in thousands) Outstanding at October 1, 2022 1,410,653 $ 23.00 Granted — — Exercised ( 294,218 ) 23.00 Cancelled/Forfeited ( 2,174 ) 23.00 Outstanding at September 30, 2023 1,114,261 23.00 6.7 7,510 Vested and exercisable at September 30, 2023 1,114,261 $ 23.00 6.7 7,510 The following table summarizes the service-based stock option activity for the year ended September 30, 2023 : Number of Weighted Weighted Aggregate (in years) (in thousands) Outstanding at October 1, 2022 3,557,194 $ 25.57 Granted 250,477 20.18 Exercised ( 355,920 ) 23.00 Cancelled/Forfeited ( 90,044 ) 25.79 Outstanding at September 30, 2023 3,361,707 25.43 7.1 19,871 Vested and exercisable at September 30, 2023 2,400,930 $ 24.59 6.8 14,561 The intrinsic value of the Company’s stock options exercised in the years ended September 30, 2023, 2022 and 2021 was $ 3.5 million, $ 3.0 million and $ 4.2 million, respectively. The tax benefit (expense) from stock options exercised during the years ended September 30, 2023, 2022 and 2021 was $ 2.0 million, $ 0.7 million and $( 1.9 ) million, respectively. Restricted Stock Awards A summary of the service-based restricted stock awards activity for the year ended September 30, 2023 was as follows: Number of Weighted Outstanding and unvested at October 1, 2022 275,628 $ 23.00 Granted — — Vested ( 173,841 ) 23.00 Forfeited ( 19,306 ) 23.00 Outstanding and unvested at September 30, 2023 82,481 $ 23.00 The total fair value of vested restricted stock awards for the years ended September 30, 2023, 2022 and 2021 was $ 2.6 million, $ 4.2 million and $ 2.7 million, respectively. Restricted Stock Units A summary of the service-based restricted stock unit awards activity for the year ended September 30, 2023 was as follows: Number of Weighted Outstanding and unvested at October 1, 2022 574,499 $ 31.14 Granted 504,951 21.22 Vested ( 246,343 ) 29.74 Forfeited ( 47,011 ) 28.06 Outstanding and unvested at September 30, 2023 786,096 $ 25.39 The total fair value of vested restricted stock units for the years ended September 30, 2023, 2022 and 2021 was $ 7.3 million, $ 2.3 million and $ 0.4 million, respectively. Performance Restricted Stock Units Performance restricted stock units were granted to officers and certain employees of the Company and represent the right to earn shares of Company common stock based on the achievement of company-wide non-GAAP performance conditions, including cumulative net sales, average return on net tangible assets and cumulative EBITDA during the three-year performance period. Compensation cost is amortized into expense over the performance period, which is generally three years, and is based on the probability of meeting performance targets. The fair value of each performance share award is based on the closing price on the date of grant. A summary of the performance-based restricted stock unit awards activity for the year ended September 30, 2023 was presented at target was as follows: Number of Weighted Outstanding and unvested at October 1, 2022 221,469 $ 37.55 Granted 319,263 20.18 Vested — — Forfeited ( 32,110 ) 35.09 Outstanding and unvested at September 30, 2023 508,622 $ 26.73

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Sep. 30, 2023
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	14. EMPLOYEE BENEFIT PLANS The Company has a 401(k) defined contribution plans (the “401(k) Plans”) for the benefit of its employees who meet certain eligibility requirements. The Company does not offer a defined benefit plan (pension plan) nor does the Company offer any other post-retirement benefits. The 401(k) Plans cover substantially all of the Company’s full-time employees. Each participant may contribute up to 85 % of his or her salary, within dollar limitations set forth by the ERISA guidelines. The 401(k) Plans match employee pre-tax and Roth IRA contributions. The Company matches 100 % of the first 1% of employee contributions, plus 50 % of the next 5% of employee contributions. The Company’s contributions to the plans totaled $ 4.9 million, $ 5.1 million and $ 4.0 million, for the years ended September 30, 2023, 2022 and 2021 , respectively.

Earnings Per Share

Earnings Per Share	12 Months Ended
Earnings Per Share	Sep. 30, 2023
Earnings Per Share [Abstract]
Earnings Per Share	15. EARNINGS PER SHARE The Company computes earnings per common share (“EPS”) under the two-class method which requires the allocation of all distributed and undistributed earnings attributable to the Company to common stock and other participating securities based on their respective rights to receive distributions of earnings or losses. The Company’s Class A common stock and Class B common stock equally share in distributed and undistributed earnings, therefore, no allocation to participating securities or dilutive securities is performed. Basic EPS attributable to common stockholders is calculated by dividing net income (loss) attributable to common stockholders by the weighted average number of shares of common stock outstanding. Diluted EPS is calculated by adjusting weighted average shares outstanding for the dilutive effect of potential common shares, determined using the treasury-stock method. For purposes of the diluted EPS calculation, restricted stock awards, restricted stock units and options to purchase shares of common stock are considered to be potential common shares. The following table sets forth the computation of the Company’s basic and diluted EPS attributable to common stockholders (in thousands, except share and per share amounts): Years Ended September 30, 2023 2022 2021 Numerator: Net income $ 67,955 $ 75,225 $ 93,150 Net income attributable to common $ 67,955 $ 75,225 $ 93,150 Denominator: Weighted average shares of common Basic 150,162,256 153,510,110 153,777,859 Diluted 150,849,896 154,517,843 156,666,394 Net income attributable to common Basic $ 0.45 $ 0.49 $ 0.61 Diluted $ 0.45 $ 0.49 $ 0.59 The following table includes the number of shares that may be dilutive common shares in the future, and were not included in the computation of diluted net income (loss) per share because the effect was anti-dilutive: Years Ended September 30, 2023 2022 2021 Stock Options 2,549,816 548,539 105,199 Restricted Stock Units 113,622 268,526 3,256

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Income Taxes	16. INCOME TAXES The Company’s operations are substantially all domestic. The components of income tax expense (benefit) consisted of the following (in thousands): Years Ended September 30, 2023 2022 2021 Current: Federal $ 25,216 $ 810 $ 200 State and local 8,200 8,260 2,939 Total current 33,416 9,070 3,139 Deferred: Federal ( 6,828 ) 19,302 26,240 State and local ( 2,659 ) 382 ( 711 ) Total deferred ( 9,487 ) 19,684 25,529 Income tax expense $ 23,929 $ 28,754 $ 28,668 The effective income tax rate was different from the statutory U.S. federal income tax rate of 21.0 %, for the years ended September 30, 2023, 2022 and 2021, due to the following (in thousands): 2023 Rate 2022 Rate 2021 Rate Income tax expense / federal statutory rate $ 19,296 21.0 % $ 21,836 21.0 % $ 25,583 21.0 % State and local taxes — net of federal expense 3,218 3.5 % 7,257 7.0 % 2,329 1.9 % Change in valuation allowance 597 0.6 % ( 350 ) ( 0.3 )% ( 220 ) ( 0.2 )% Stock-based compensation 721 0.8 % 145 0.1 % 1,379 1.1 % Non-deductible transaction costs — 0.0 % — 0.0 % 544 0.4 % Executive compensation 608 0.7 % 364 0.4 % 704 0.6 % Federal research and development credit ( 746 ) ( 0.8 )% ( 703 ) ( 0.7 )% ( 1,829 ) ( 1.4 )% Meals and entertainment 284 0.3 % 224 0.2 % 267 0.2 % Other ( 49 ) ( 0.1 )% ( 19 ) 0.0 % ( 89 ) ( 0.1 )% Income tax expense / effective tax rate $ 23,929 26.0 % $ 28,754 27.7 % $ 28,668 23.5 % The effective income tax rate was 26.0 % for the year ended September 30, 2023 compared to 27.7 % for the year ended September 30, 2022. The 2023 effective income tax rate was positively impacted by decreased State tax expense recognized in the current period partially offset by a net increase in valuation allowances and disallowed compensation costs. The components of the deferred tax assets and liabilities consisted of the following (in thousands): As of September 30, 2023 2022 Deferred tax asset: State loss carryforwards and other benefits $ 15,744 $ 13,699 Inventory reserves 14,203 13,852 Warranty reserves 4,148 3,839 Accrued expenses 11,996 10,607 Stock-based compensation 13,502 12,185 Lease liabilities 24,063 25,034 Valuation allowance ( 5,557 ) ( 4,960 ) Total deferred tax assets 78,099 74,256 Deferred tax liabilities: Intangible assets — net 37,272 42,197 Property, plant and equipment 74,611 73,471 Right-of-use assets 21,728 23,237 Unrealized gain in other comprehensive income 615 — Indemnification receivable related to warranty reserves 203 546 Total deferred tax liabilities 134,429 139,451 Net deferred tax liability $ 56,330 $ 65,195 At September 30, 2023 , the Company has no net operating loss carryforwards for federal income tax purposes. Additionally, the Company has approximately $ 83.9 million of net operating loss carryforwards for state and local tax purposes, which expire in varying amounts beginning in 2024 and through 2043 . Furthermore, some net operating loss carry forwards for state and local purposes have indefinite carryforward periods. Utilization of the NOL carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended (the Code), and similar state law due to ownership changes that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. The valuation allowance was determined in accordance with the provisions of ASC 740, Income Taxes , which requires that a valuation allowance be established and maintained when management’s analysis indicates it is “not more likely than not” that all or a portion of deferred tax assets will be realized. The valuation allowance for certain net deferred tax assets of $ 5.6 million and $ 5.0 million at September 30, 2023 and 2022, respectively, is attributable to the uncertainty as to the realization of state deferred tax assets related to Idaho tax credit carryforwards and Pennsylvania state tax loss carryforwards at certain U.S. subsidiaries of the Company (The AZEK Group LLC and Scranton Products, Inc.). The activity in the valuation allowance consisted of the following (in thousands): As of September 30, 2023 2022 Beginning balance $ 4,960 $ 5,310 Expense 597 ( 350 ) Ending balance $ 5,557 $ 4,960 A reconciliation of the beginning and ending balances for liabilities associated with unrecognized tax benefits consisted of the following (in thousands): As of September 30, 2023 2022 Beginning balance $ 780 $ 955 Unrecognized tax benefits related to prior years 70 ( 230 ) Unrecognized tax benefits related to the current year 50 55 Ending balance $ 900 $ 780 Unrecognized tax benefits of $ 0.9 million and $ 0.8 million are recorded at September 30, 2023 and 2022 , respectively. The total liabilities associated with the unrecognized tax benefits that, if recognized, would impact the Company’s effective tax rate were $ 0.9 million and $ 0.8 million at September 30, 2023 and 2022, respectively. When applicable, the Company’s practice is to recognize interest and penalties related to uncertain income tax positions in income tax expense. For the years ended September 30, 2023, 2022 and 2021 the amounts recognized by the Company for interest and penalties were not material. The corresponding liability recorded in the Consolidated Balance Sheets as of September 30, 2023 and 2022 was also not material. The Company and its subsidiaries file U.S. federal income tax returns. The Company and its subsidiaries’ federal income tax returns for tax years 2020 and beyond are open tax years subject to examination by the Internal Revenue Service (“IRS”). The Company also has net operating loss carry-forwards from prior to 2020, which are subject to examination upon future utilization of such losses. The Company and its subsidiaries also file income tax returns in various state jurisdictions, as appropriate, with varying statutes of limitation. These returns are not material to the consolidated income tax provision.

Commitments And Contingencies

Commitments And Contingencies	12 Months Ended
Commitments And Contingencies	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	17. COMMITMENTS AND CONTINGENCIES Raw Material and Fixed Asset Purchase Commitments The Company fulfills requirements for raw materials under both purchase orders and supply contracts. In the year ended September 30, 2023, the Company purchased substantially all of its raw materials, other than resins, under purchase orders which do not involve long-term supply commitments. Substantially all of the Company’s resins are purchased under supply contracts that may average approximately one to two years, for which pricing is variable based on certain industry-based market indices. The resin supply contracts are negotiated annually and generally provide that the Company is obligated to purchase a minimum amount of resins from each supplier. As of September 30, 2023 , the Company has no purchase commitments under material supply contracts through the calendar year ending December 31, 2023. As of September 30, 2023 and 2022 , the Company had committed to purchase $ 0.4 million and $ 0.4 million of equipment, respectively. Legal Proceedings In the normal course of the Company’s business, it is at times subject to pending and threatened legal actions, in some cases for which the relief or damages sought may be substantial. Although the Company is not able to predict the outcome of such actions, after reviewing all pending and threatened actions with counsel and based on information currently available, management believes that the outcome of such actions, individually or in the aggregate, will not have a material adverse effect on the Company’s results of operations or financial position. However, it is possible that the ultimate resolution of such matters, if unfavorable, may be material to the Company’s results of operations in a particular future period as the time and amount of any resolution of such actions and its relationship to the future results of operations are not currently known. In evaluating whether to accrue for losses associated with legal or environmental contingencies, it is our policy to take into consideration factors such as the facts and circumstances asserted, our historical experience with contingencies of a similar nature, the likelihood of our prevailing and the severity of any potential loss. For some matters, no accrual is established because we have assessed our risk of loss to be remote. Where we have determined that the risk of loss is probable and such losses are reasonably estimable, we record an accrual. While we regularly review the status of, and our estimates of potential liability associated with, the contingencies to determine the adequacy of any associated accruals and related disclosures, the ultimate amount of loss may differ from our estimates. Loss Contingencies During the year ended September 30, 2019, the Company was made aware of a worker’s compensation case that became reasonably possible to give rise to a liability. Discovery has been completed, and the Company filed motions for summary judgment in April 2023. On November 8, 2023, the court granted the Company's motions for summary judgment seeking to dismiss Scranton Products Inc. and The AZEK Company Inc. but denied the Company's motions for summary judgment seeking to dismiss The AZEK Group LLC and Vycom Corp. A trial date has been set for May 2024. In the normal course of the Company’s business, it is at times subject to various other legal actions, in some cases for which the relief or damages sought may be substantial. Although the Company is not able to predict the outcome of legal actions to which it may be subject, after reviewing all pending and threatened actions with counsel and based on information currently available, management believes that the outcome of such actions, individually or in the aggregate, will not have a material adverse effect on the Company’s results of operations or financial position. However, it is possible that the ultimate resolution of such matters, if unfavorable, may be material to the Company’s results of operations in a particular future period as the time and amount of any resolution of such actions and its relationship to the future results of operations are not currently known. The Company accrues for losses when they are probable of occurrence and such losses are reasonably estimable. Legal costs expected to be incurred are accounted for as they are incurred.

Condensed Financial Information

Condensed Financial Information of Registrant (Parent Company Only)	12 Months Ended
	Sep. 30, 2023
Condensed Financial Information Disclosure [Abstract]
Condensed Financial Information of Registrant (Parent Company Only)	. CONDENSED FINANCIAL INFORMATION OF REGISTRANT (PARENT COMPANY ONLY) The AZEK Company Inc. (parent company only) Balance Sheets (In thousands of U.S. dollars, except for share and per share amounts) As of September 30, 2023 2022 ASSETS: Non-current assets: Investments in subsidiaries $ 1,429,643 $ 1,444,443 Total non-current assets 1,429,643 1,444,443 Total assets $ 1,429,643 $ 1,444,443 LIABILITIES AND STOCKHOLDERS’ EQUITY: Total liabilities $ — $ — Stockholders’ equity: Preferred stock, $ 0.001 par value; 1,000,000 shares authorized and no shares issued — — Class A common stock, $ 0.001 par value; 1,100,000,000 shares authorized, 155,967,736 shares issued at September 30, 2023, and 155,157,220 issued 156 155 Class B common stock, $ 0.001 par value; 100,000,000 shares authorized, 100 shares — — Additional paid-in capital 1,662,322 1,630,378 Accumulated deficit ( 45,047 ) ( 113,002 ) Accumulated other comprehensive income (loss) 1,878 — Treasury stock, at cost, 8,268,423 shares at September 30, 2023 and 4,116,570 shares at September 30, 2022 ( 189,666 ) ( 73,088 ) Total stockholders’ equity 1,429,643 1,444,443 Total liabilities and stockholders’ equity $ 1,429,643 $ 1,444,443 The AZEK Company Inc. (parent company only) Statements of Comprehensive Income (In thousands of U.S. dollars) Years Ended September 30, 2023 2022 2021 Net income of subsidiaries $ 67,955 $ 75,225 $ 93,150 Net income of subsidiaries $ 67,955 $ 75,225 $ 93,150 Comprehensive income $ 69,833 $ 75,225 $ 93,150 The AZEK Company Inc. did not have any cash as of September 30, 2023, 2022 and 2021, accordingly a Statement of Cash Flows has not been presented. Basis of Presentation The parent company financial statements should be read in conjunction with the Company’s Consolidated Financial Statements and the accompanying notes thereto. For purposes of this condensed financial information, the Company’s wholly owned and majority owned subsidiaries are recorded based upon its proportionate share of the subsidiaries’ net assets (similar to presenting them on the equity method). Since the restricted net assets of The AZEK Company Inc. and its subsidiaries exceed 25 % of the consolidated net assets of the Company and its subsidiaries, the accompanying condensed parent company financial statements have been prepared in accordance with Rule 12-04, Schedule 1 of Regulation S-X. This information should be read in conjunction with the accompanying Consolidated Financial Statements. Dividends from Subsidiaries There were $ 115.5 million, $ 73.1 million and $ 0.0 million cash dividends paid to The AZEK Company Inc. from the Company’s consolidated subsidiaries during each of the years ended September 30, 2023, 2022 and 2021 . Cash dividends of $ 115.5 million were used to fund the $ 36.0 million share repurchase from the underwriter upon completion of the secondary offering and $ 79.5 million share repurchase on the open market during the year ended September 30, 2023. Cash dividends of $ 73.1 million were used to fund the $ 50.0 million ASR and $ 23.1 million share repurchase on the open market during the year ended September 30, 2022. Restricted Payments The AZEK Group LLC is party to the Revolving Credit Facility and the Term Loan Agreement originally executed on September 30, 2013, both of which have been amended and extended from time to time. The obligations under the Revolving Credit Facility and Term Loan Agreement are secured by substantially all of the present and future assets of the borrowers and guarantors, including equity interests of their domestic subsidiaries, subject to certain exceptions. The obligations under the Revolving Credit Facility and Term Loan Agreement are guaranteed by the Company and its wholly owned domestic subsidiaries other than certain immaterial subsidiaries and other excluded subsidiaries. The AZEK Group LLC is not permitted to make certain payments unless those payments are consistent with exceptions outlined in the agreements. These payments include repurchase of equity interests, fees associated with a public offering, income taxes due in other applicable payments. Further, the payments are only permitted if certain conditions are met related to availability and fixed charge coverage as defined in the Revolving Credit Facility and described in Note 7 to these Consolidated Financial Statements.

Subsequent Events

Subsequent Events	12 Months Ended
Subsequent Events	Sep. 30, 2023
Subsequent Events [Abstract]
Subsequent Events	. SUBSEQUENT EVENTS On October 10, 2023, the Company entered into a definitive agreement to sell its Vycom business, a division of its Commercial segment, to Ohio-based Plaskolite, LLC. The transaction closed on November 1, 2023 . As of September 30, 2023, the transaction did not meet the criteria to be classified as held for sale in our Consolidated Balance Sheet.

Organization and Summary of S_2

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company operates on a fiscal year ending September 30. The accompanying Consolidated Financial Statements and notes have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The Consolidated Financial Statements include the assets, liabilities and results of operations of the Company and its wholly owned subsidiaries. All material intercompany transactions and balances have been eliminated in consolidation. The Company’s financial condition and results of operations are affected by a number of factors, including, but not limited to, the cost to manufacture and distribute products, cost of raw materials, inflation, consumer spending and preferences, interest rates, the impact of any supply chain disruptions, economic conditions, and/or any adverse effects from global health pandemics, geopolitical conflicts and other factors beyond the Company’s control. Management cannot predict the degree to, or the period over, which the Company may be affected by such factors.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Significant estimates include revenue recognition, reserves for excess inventory, inventory obsolescence, inventory valuation, product warranties, customer rebates, stock-based compensation, litigation, income taxes, contingent consideration, goodwill and intangible asset valuation and accounting for long-lived assets. Management’s estimates and assumptions are evaluated on an ongoing basis and are based on historical experience, current conditions and available information. Actual results may differ from estimated amounts. Estimates are revised as additional information becomes available.
Seasonality	Seasonality Although the Company generally has demand for its products throughout the year, its sales have historically experienced some seasonality. The Company has typically experienced higher levels of sales of its residential products in the second fiscal quarter of the year as a result of its “early buy” sales, which encourages dealers to stock its residential products. The Company has generally experienced lower levels of sales of residential products in the first fiscal quarter due to adverse weather conditions in certain markets during the winter season. Although its products can be installed year-round, weather conditions can impact the timing of the sales of certain products. In addition, the Company has experienced higher levels of sales of its bathroom partition products and its locker products during the second half of its fiscal year, which includes the summer months when schools are typically closed and therefore are more likely to undergo remodel activities.
Revenue Recognition	Revenue Recognition The Company sells its products to residential and commercial markets. The Company’s Residential segment principally generates revenue from the manufacture and sale of its premium, low-maintenance composite decking, railing, trim, moulding, pergolas and cabanas and accessories. The Company’s Commercial segment generates revenue from the sale of its partition and locker systems along with plastic sheeting and other non-fabricated products for special applications in industrial markets. The Company recognizes revenues when control of the promised goods is transferred to the Company’s customers in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods, at a point in time, when shipping occurs. Each product the Company transfers to the customer is considered one performance obligation. The Company has elected to account for shipping and handling costs as activities to fulfill the promise to transfer the goods. As a result of this accounting policy election, the Company does not consider shipping and handling activities as promised services to its customers. Shipping and handling costs billed to customers are recorded in net sales. The Company records all shipping and handling costs as “Cost of sales”. Customer contracts are typically fixed price and short-term in nature. The transaction price is based on the product specifications and is determined at the time of order. The Company does not engage in contracts greater than one year, and therefore does not have any incremental costs capitalized as of September 30, 2023 or September 30, 2022. The Company may offer various sales incentive programs throughout the year. It estimates the amount of sales incentive to allocate to each performance obligation, or product shipped, using the most-likely-amount method of estimation, based on sales to the direct customer or sell-through customer. The estimate is updated each reporting period and any changes are allocated to the performance obligations on the same basis as at inception. Changes in estimate allocated to a previously satisfied performance obligation are recognized as part of net revenue in the period in which the change occurs under the cumulative catch-up method. In addition to sales incentive programs, the Company may offer a payment discount, if payments are received within 30 days. The Company estimates the payment discount that it believes will be taken by the customer based on prior history and using the most-likely-amount method of estimation. The Company believes the most-likely-amount method best predicts the amount of consideration to which it will be entitled. The payment discounts are also reflected as part of net revenue. The total amount of incentives were $ 132.6 million , $ 105.8 million and $ 92.5 million for the years ended September 30, 2023, 2022 and 2021, respectively. The Company records deferred revenue when cash payments are received or due in advance of the Company’s performance.
Earnings Per Share	Earnings Per Share Basic net income per common share is computed based on the weighted average number of common shares outstanding. Potentially dilutive shares are included in the diluted per-share calculations using the treasury stock method for the periods in fiscal year 2020 when the effect of their inclusion is dilutive. Refer to Note 15 for additional information.
Advertising Costs	Advertising Costs Advertising costs primarily relate to trade publication advertisements, cooperative advertising, product brochures and samples. Such costs are expensed as incurred and are included in “Selling, general and administrative expenses” within the Consolidated Statements of Comprehensive Income. Total advertising expenses were approximately $ 62.2 million , $ 52.5 million and $ 37.8 million for the years ended September 30, 2023, 2022 and 2021 , respectively.
Research and Development Costs	Research and Development Costs Research and development costs primarily relate to new product development, product claims support and manufacturing process improvements. Such costs are expensed as incurred and are included in “Selling, general and administrative expenses” within the Consolidated Statements of Comprehensive Income. Total research and development expenses were approximately $ 9.2 million , $ 9.5 million , and $ 7.4 million , for the years ended September 30, 2023, 2022 and 2021 , respectively.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers cash and highly liquid investments with an original maturity of three months or less to be cash and cash equivalents. Cash and cash equivalents are stated at cost, which approximates or equals fair value due to their short-term nature.
Concentrations and Credit Risk	Concentrations and Credit Risk The Company’s financial instruments that are exposed to concentrations of credit risk consist primarily of cash and cash equivalents and trade accounts receivable. As of September 30, 2023, cash and cash equivalents were maintained at major financial institutions in the United States, and current deposits are in excess of insured limits. The Company believes these institutions have sufficient assets and liquidity to conduct their operations in the ordinary course of business with little or no credit risk to the Company. The Company has not experienced any losses in such accounts. Sales to certain Residential segment distributors accounted for 10 % or more of the Company’s total net sales in 2023, 2022 and 2021 were as follows: Years Ended September 30, 2023 2022 2021 Distributor A 18.7 % 19.3 % 23.3 % At September 30, 2023 , receivables from one customer represented 17.2 % of gross trade receivables. At September 30, 2022 , two customers each represented more than 10 % of gross trade receivables: Customer A was 10.6 % and Customer B was 14.8 %. For each year ended September 30, 2023, 2022 and 2021 , approximately 17 %, 16 % and 18 %, respectively, of the Company’s materials purchases were purchased from its largest supplier.
Allowance for losses	Allowance for losses The Company routinely assesses the financial strength of its customers and believes that its trade receivables credit risk exposure is limited. The allowance for losses is our estimate of credit losses associated with trade receivables balances. An estimate of expected credit losses is recognized as a valuation allowance and adjusted each reporting period. The estimate is based on the current expected credit loss model and is determined by management in the course of regularly evaluating individual customer receivables. This evaluation takes into consideration a customer’s financial condition and credit history, as well as current economic conditions. Amounts are written-off if and when they are determined to be uncollectible.
Inventories	Inventories Inventories (mainly petrochemical resin in raw materials and finished goods), are valued at the lower of cost or net realizable value and are reduced for slow-moving and obsolete inventory. Management assesses the need for, and the amount of, obsolescence write-down based on customer demand of the item, the quantity of the item on hand and the length of time the item has been in inventory. Further, management also considers net realizable value in assessing inventory balances. Inventory costs include those costs directly attributable to products, including all manufacturing overhead but excluding costs to distribute. The inventories cost is recorded at standard cost, which approximates actual cost, on the first-in first-out basis (“FIFO”). During the fourth quarter of fiscal year 2022, the Company updated the process by which it estimates the value of its inventory. This included updating the assumptions that are used in determining and treating certain capitalized costs, primarily by incorporating the impacts of changes in the amount of recycled content introduced into the Company’s products since its last standard costing revaluation.
Vendor Rebates	Vendor Rebates Certain vendor rebates and incentives are earned by the Company only when specified levels of periodic purchases are achieved. These vendor rebates are recognized based on a systematic and rational allocation of the cash consideration offered in respect of each of the underlying transactions, provided the amounts are probable and reasonably estimable. The Company records the incentives as a reduction in the cost of inventory. The Company records such incentives during interim periods based on actual results achieved on a year-to-date basis and its expectation that purchase levels will be obtained to earn the rebate.
Customer Rebate	Customer Rebates The Company offers rebates to customers based on total amounts purchased by each customer during each calendar year. The Company provides for the estimated cost of rebates at the time revenue is recognized based on rebate program rates and anticipated sales to each customer eligible for rebates and other available information. Management reviews and adjusts these estimates, if necessary, based on the differences between actual experience and historical estimates. Refer to Note 2 for additional information.
Product Warranties	Product Warranties The Company provides product assurance warranties of various lengths and terms to certain customers based on standard terms and conditions. The Company provides for the estimated cost of warranties at the time revenue is recognized based on management’s judgment, considering such factors as cost per claim, historical experience, anticipated rates of claims, and other available information. Management reviews and adjusts these estimates, if necessary, based on the differences between actual experience and historical estimates. Refer to Note 8 for additional information.
Property, Plant and Equipment, Net	Property, Plant and Equipment, Net Property, plant and equipment (“PP&E”) is recorded at cost, net of accumulated depreciation. Major additions and betterments are capitalized while repair and/or maintenance expenses are charged to operations when incurred. Construction in progress is also recorded at cost and includes capitalized interest, if material. Depreciation for financial reporting purposes is computed using the straight-line method over the following estimated useful lives of the assets: Land improvements 10 years Building and improvements 7 - 40 years Manufacturing equipment 1 - 15 years Office furniture and equipment 3 - 12 years Vehicles 5 years Computer equipment 3 - 7 years Leasehold improvements are recorded at cost and depreciated over the standard life of the type of asset or the remaining life of the lease, whichever is shorter. Equipment held under capital leases is stated at the lower of the fair value of the asset or the net present value of the future minimum lease payments at the inception of the lease. For equipment held under capital leases, depreciation is computed using the straight-line method over the shorter of the estimated useful lives of the leased assets or the related lease term and is included within depreciation expense. PP&E is evaluated for impairment at the asset group level. If a triggering event suggests that a potential impairment has occurred, recoverability of these assets is assessed by evaluating whether or not future estimated undiscounted net cash flows are less than the carrying amount of the assets. If the estimated cash flows are less than the carrying amount, the assets are written down to their fair value through an impairment loss recognized as a non-cash component of “Operating income (loss)” within the Consolidated Statements of Comprehensive Income. The Company did not record an impairment charge for the years ended September 30, 2023, 2022 and 2021. During the year ended September 30, 2023, 2022 and 2021, the Company recognized losses on disposal of fixed assets in the ordinary course of business of $ 0.2 million , $ 0.5 million and $ 1.0 million , respectively, the losses related to assets in the Residential segment. These losses are classified as “Loss on disposal of property, plant and equipment” in a separate caption within the Consolidated Statements of Comprehensive Income within “Operating income”.
Leases	Leases Right-of-use (“ROU”) assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. The discount rate used to calculate the present value represents our incremental borrowing rate and is calculated based on the treasury yield curve commensurate with the term of each lease, and a spread representative of our borrowing costs. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Leases may be classified as either operating leases or finance leases. We have made an accounting policy election to not include leases with an initial term of 12 months or less on the balance sheet. See Note 9—Leases for additional information.
Goodwill	Goodwill The Company accounts for goodwill as the excess of the purchase price over the net amount of identifiable assets acquired and liabilities assumed in a business combination measured at fair value. The Company assigns goodwill to six reporting units based on which reporting unit is expected to benefit from the business combination as of the acquisition date. Goodwill is not subject to amortization; rather, the Company tests goodwill for impairment annually during the fourth fiscal quarter ended September 30 or more frequently if an event occurs or circumstances change in the interim that would more likely than not reduce the fair value of the asset below the carrying amount. The impairment evaluation may begin with a qualitative assessment of the factors that could impact the significant inputs used to estimate fair value to determine if it is more likely than not that the fair value of the reporting unit is less than its carrying amount or the Company may elect to bypass the qualitative assessment and proceed to a quantitative assessment to determine if goodwill is impaired. In quantitative impairment tests, if the estimated fair value of a reporting unit exceeds the carrying value, the Company considers that goodwill is not impaired. If the carrying value exceeds estimated fair value, there is an impairment of goodwill and an impairment loss is recorded. The Company calculates the impairment loss by comparing the fair value of the reporting unit less the carrying amount, including goodwill. Goodwill impairment would be limited to the carrying value of the goodwill. In performing the quantitative test, the Company measures the fair value of the reporting units to which goodwill is allocated using an income-based approach, a generally accepted valuation methodology, and relevant data available through the testing date. Under the income approach, fair value is determined using a discounted cash flow method, projecting future cash flows of each reporting unit, as well as a terminal value, and discounting such cash flows at a rate of return that reflects the relative risk of the cash flows. The key assumptions and factors used in this approach include, but are not limited to, revenue growth rates and profit margins based on internal Company forecasts, discount rates, perpetuity growth rates, future capital expenditures, and working capital requirements, among others, and a review of comparable market multiples for the industry segment as well as historical operating trends for the Company. The Company completed the annual goodwill impairment tests as of August 1, 2023, 2022 and 2021 , using a quantitative assessment for all six of the reporting units, a qualitative assessment for five reporting units and a quantitative assessment for one of the reporting units, and a qualitative assessment for three reporting units and a quantitative assessment for one of the reporting units, respectively. As a result of these respective annual assessments, the Company noted that the fair value of each reporting unit was determined to be in excess of the carrying value and as such, there were no impairment charges for the years ended September 30, 2023, 2022 and 2021 . Refer to Note 5 for additional information.
Intangible Assets, Net	Intangible Assets, Net Amortizable intangible assets include proprietary knowledge, trademarks, customer relationships and other intangible assets. The Company does not have any indefinite lived intangible assets other than goodwill. The intangible assets are being amortized on an accelerated basis using the sum of the years’ digits method over their estimated useful lives, which range from 3 to 20 years, reflecting the pattern in which the economic benefits are consumed or otherwise used up. The Company evaluates whether events or circumstances have occurred that warrant a revision to the remaining useful lives of intangible assets. In cases where a revision is deemed appropriate, the remaining carrying amounts of the intangible assets are amortized over the revised remaining useful lives. The Company evaluates amortizable intangible assets for potential impairment whenever events or changes in circumstances indicate that the carrying amounts of the assets may not be fully recoverable. If a triggering event suggests that a potential impairment has occurred, recoverability of these assets is assessed by evaluating the probability that future estimated undiscounted net cash flows will be less than the carrying amount of the long-lived assets. If the estimated cash flows are less than the carrying amount of the long-lived assets, the assets are written down to their fair value through an impairment loss recognized as a non-cash component of “Operating income (loss)”. The Company did not record an impairment charge for the years ended September 30, 2023, 2022 and 2021 . Refer to Note 5 for additional information.
Deferred Financing Costs, Net	Deferred Financing Costs, Net The Company has recorded deferred financing costs incurred in conjunction with its debt obligations. The Company amortizes debt issuance costs over the remaining life of the related debt using the straight-line method for the Revolving Credit Facility and the effective interest method for other debt. Deferred financing costs, net of accumulated amortization, are presented as “Other assets” (non-current) in the Consolidated Balance Sheets, insofar as they relate to the Revolving Credit Facility. Deferred financing costs related to the 2022 Term Loan Agreement are recorded as a reduction of “Long-term debt – less current portion” in the Consolidated Balance Sheets. Refer to Note 7 for additional information.
Stock-Based Compensation	Stock-Based Compensation The Company determines the expense for all employee stock-based compensation awards by estimating their fair value and recognizing such value as an expense, on a straight-line, ratable or cliff basis, depending on the award, in the Consolidated Financial Statements over the requisite service period in which employees earn the awards. The Company estimates the fair value for service-based awards granted to employees using the Black Scholes pricing model. The fair value of performance-based awards that are expected to vest is recognized as compensation expense on a straight-line basis over the requisite service period. The fair value of service-based awards that are expected to vest is recognized as compensation expense on either (1) straight-line basis, (2) a ratable vesting basis or (3) a cliff vesting basis. The Company accounts for forfeitures as they occur. To determine the fair value of a stock-based award using Black Scholes models, the Company makes assumptions regarding the risk-free interest rate, expected future volatility, expected dividend yield and performance period. The risk-free rate is based on the U.S. treasury yield curve in effect at the time of grant. The Company estimates the expected volatility of the share price by reviewing the estimated post-IPO volatility levels of its common stock in conjunction with the historical volatility levels of public companies that operate in similar industries or are similar in terms of stage of development or size and then projecting this information toward its future expected volatility. The Company exercises judgment in selecting these companies, as well as in evaluating the available historical and implied volatility for these companies. Dividend yield is determined based on the Company’s future plans to pay dividends. The Company calculates the performance period based on the specific market condition to be achieved and derived from estimates of future performance. The Company calculates the expected term in years for each stock option using a simplified method based on the average of each option’s vesting term and original contractual term. The simplified method is used due to the lack of sufficient historical data available to provide a reasonable basis upon which to estimate the expected term of each stock option. Refer to Note 13 for additional information.
Estimated Fair Value of Financial Instruments	Estimated Fair Value of Financial Instruments The carrying amounts for the Company’s financial instruments classified as current assets and liabilities, including cash and cash equivalents, trade accounts receivable and accrued expenses and accounts payable, approximate fair value due to their short maturities. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement: Level 1—Quoted prices in active markets for identical assets or liabilities. Level 2—Observable inputs other than quoted prices in active markets for identical assets and liabilities, quoted prices for identical or similar assets or liabilities in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Inputs that are generally unobservable and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability . Refer to Note 10 for additional information.
Derivatives	Derivatives The Company uses interest rate swap agreements to hedge its exposure to interest rate risk on its senior secured credit facilities. The Company designates derivatives that meet specific accounting criteria as qualifying hedges at inception. These criteria require the Company to have the expectation that the derivative will be highly effective at offsetting changes in the fair value or expected cash flows of the hedged exposure, both at inception of the hedging relationship and on an ongoing basis. The Company recognizes all derivative instruments at fair value and classifies them on the balance sheet as either Other current assets, Other assets, Accrued expenses and other liabilities or Other non-current liabilities. The interest rate swap agreements are designated as cash flow hedges. For cash flow hedges, the Company records the effective portion of the change in fair value of the derivative as part of Accumulated other comprehensive income and recognizes those changes in earnings in the period the hedged transaction affects earnings. The Company recognizes any ineffective portion of the change in the fair value of the derivative immediately in earnings. See Note 10 for additional information.
Income Taxes	Income Taxes Income taxes are provided on income reported for financial statement purposes, adjusted for permanent differences between financial statement reporting and income tax regulations. A valuation allowance is established whenever management believes that it is more likely than not that deferred tax assets may not be realizable. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the year in which the deferred tax assets or liabilities are expected to be realized or settled. The realization of the net deferred tax assets is primarily dependent on estimated future taxable income. A change in the Company’s estimate of future taxable income may require an increase or decrease in the valuation allowance. A liability for uncertain tax positions is recorded whenever management believes it is not more-likely than-not the position will be sustained on examination based solely on its technical merits. Interest and penalties related to underpayment of income taxes are classified as income tax expense. It is inherently difficult and subjective to estimate such amounts, as the Company has to determine the probability of various possible outcomes. The Company reevaluates these uncertain tax positions on a quarterly basis. This evaluation is based on factors including, but not limited to, changes in facts or circumstances, changes in tax law, effectively settled issues under audit, voluntary settlements and new audit activity. Such a change in recognition or measurement would result in the recognition of a tax benefit or an additional charge to the tax provision.
Revision of Previously Filed Quarterly Reports	Revision of Previously Filed Quarterly Reports During the fourth quarter of fiscal year 2023, the Company identified an error in its statement of cash flows related to classification of contingent consideration payments in connection with a recent acquisition. In the six and nine month periods ended March 31, 2023 and June 30, 2023, the Company classified such payments made more than three months from the date of the acquisition of $ 1.0 million and $ 5.8 million, respectively, within the operating activities section as opposed to within the financing activities section of the statement of cash flows. The Company evaluated the impact of the errors individually and in the aggregate on its previously issued financial statements, from both a qualitative and a quantitative perspective, and concluded that the errors were not material to any of the prior periods or to the current period financial statements. The Company determined that it will be appropriate to revise the related historical periods within statement of cash flows in the quarterly reports to be filed for the six and nine month periods ending March 31, 2024 and June 30, 2024 to achieve comparability in the financial statements.
Recently Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements On October 1, 2021, the Company adopted ASU No. 2019-12, Income Taxes (Topic 740)—Simplifying the Accounting for Income Taxes . This standard simplifies the accounting for income taxes by removing certain exceptions to general principles in Topic 740 and clarifying and amending existing guidance. The adoption of the standard did not have a material impact on the Company’s Consolidated Financial Statements. Recently Issued Accounting Pronouncements None.

Organization and Summary of S_3

Organization and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Schedules of Concentration of Risk Percentage	Years Ended September 30, 2023 2022 2021 Distributor A 18.7 % 19.3 % 23.3 %
Schedule of Estimated Useful Lives of the Assets	Depreciation for financial reporting purposes is computed using the straight-line method over the following estimated useful lives of the assets: Land improvements 10 years Building and improvements 7 - 40 years Manufacturing equipment 1 - 15 years Office furniture and equipment 3 - 12 years Vehicles 5 years Computer equipment 3 - 7 years

Revenue (Tables)

Revenue (Tables)	12 Months Ended
Revenue (Tables)	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Summary of Rebate Activity	The rebate activity was as follows (in thousands). As of September 30, 2023 2022 2021 Beginning balance $ 56,542 $ 47,648 $ 32,679 Rebate expense 106,762 88,057 76,763 Rebate payments ( 96,346 ) ( 79,163 ) ( 61,794 ) Ending balance $ 66,958 $ 56,542 $ 47,648

Inventories (Tables)

Inventories (Tables)	12 Months Ended
Inventories (Tables)	Sep. 30, 2023
Inventory Disclosure [Abstract]
Schedule of Inventories	Inventories consisted of the following (in thousands): As of September 30, 2023 2022 Raw materials $ 67,330 $ 72,464 Work in process 37,038 39,829 Finished goods 116,733 187,612 Total inventories $ 221,101 $ 299,905

Property, Plant and Equipment_2

Property, Plant and Equipment - Net (Tables)	12 Months Ended
Property, Plant and Equipment - Net (Tables)	Sep. 30, 2023
Property, Plant and Equipment [Abstract]
Summary of Property, Plant and Equipment - Net	Property, plant and equipment — net consisted of the following (in thousands): As of September 30, 2023 2022 Land and improvements $ 4,829 $ 3,350 Buildings and improvements 129,031 110,300 Manufacturing equipment 624,754 540,536 Computer equipment 32,300 28,198 Furnitures and fixtures 7,290 6,867 Vehicles 1,105 941 Total property, plant and equipment 799,309 690,192 Construction in progress 94,422 140,566 893,731 830,758 Accumulated depreciation ( 392,708 ) ( 312,845 ) Total property, plant and equipment – net $ 501,023 $ 517,913

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Net (Tables)	12 Months Ended
Goodwill and Intangible Assets - Net (Tables)	Sep. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Changes in Carrying Amount of Goodwill	Goodwill consisted of the following (in thousands): Residential Commercial Total Goodwill before impairment as of September 30, 2022 $ 953,606 $ 72,589 $ 1,026,195 Accumulated impairment losses as of September 30, 2022 — ( 32,200 ) ( 32,200 ) Goodwill, net as of September 30, 2022 $ 953,606 $ 40,389 $ 993,995 Acquisitions 276 — 276 Goodwill before impairment as of September 30, 2023 $ 953,882 $ 72,589 $ 1,026,471 Accumulated impairment losses as of September 30, 2023 — ( 32,200 ) ( 32,200 ) Goodwill, net as of September 30, 2023 $ 953,882 $ 40,389 $ 994,271
Summary of Finite-lived Intangible Assets	Finite-lived intangible assets consisted of the following (in thousands): As of September 30, 2023 Lives in Gross Accumulated Net Propriety knowledge 10 — 15 $ 300,400 $ ( 253,608 ) $ 46,792 Trademarks 5 — 20 230,240 ( 164,759 ) 65,481 Customer relationships 12 — 19 176,852 ( 92,268 ) 84,584 Patents 9 — 10 8,500 ( 5,913 ) 2,587 Other intangible assets 3 — 15 4,076 ( 4,023 ) 53 Total intangible assets $ 720,068 $ ( 520,571 ) $ 199,497 As of September 30, 2022 Lives in Gross Accumulated Net Propriety knowledge 10 — 15 $ 300,400 $ ( 236,024 ) $ 64,376 Trademarks 5 — 20 230,240 ( 151,259 ) 78,981 Customer relationships 12 — 19 176,852 ( 78,015 ) 98,837 Patents 9 — 10 8,500 ( 4,950 ) 3,550 Other intangible assets 3 — 15 4,076 ( 3,985 ) 91 Total intangible assets $ 720,068 $ ( 474,233 ) $ 245,835
Summary of Expected Amortization Expense Relating to Intangible Assets	Amortization expense relating to these amortizable intangible assets as of September 30, 2023, is expected to be as follows (in thousands): 2024 $ 40,748 2025 35,204 2026 29,660 2027 24,115 2028 18,572 Thereafter 51,198 Total $ 199,497

Composition of Certain Balanc_2

Composition of Certain Balance Sheet Accounts (Tables)	12 Months Ended
Composition of Certain Balance Sheet Accounts (Tables)	Sep. 30, 2023
Composition Of Certain Balance Sheet Accounts Disclosure [Abstract]
Summary of Allowance for Losses	Allowance for losses consisted of the following (in thousands): As of September 30, 2023 2022 2021 Beginning balance $ 1,397 $ 1,109 $ 1,332 Provision 731 290 342 Bad debt write-offs ( 355 ) ( 2 ) ( 565 ) Ending balance $ 1,773 $ 1,397 $ 1,109
Schedule of Accrued Expenses and Other Liabilities	Accrued expenses consisted of the following (in thousands): As of September 30, 2023 2022 Employee related liabilities $ 34,313 $ 36,866 Taxes 6,959 142 Lease liability operating 4,180 5,223 Customer deposits 4,152 2,494 Marketing 3,868 4,272 Construction in progress 2,863 9,032 Lease liability finance 2,777 2,366 Warranty 2,739 2,900 Utilities 2,141 794 Professional fees 2,073 2,089 Freight 1,242 1,821 Commissions 991 1,032 Other 3,696 3,558 Total accrued expenses and other current liabilities $ 71,994 $ 72,589

Debt (Tables)

Debt (Tables)	12 Months Ended
Debt (Tables)	Sep. 30, 2023
Debt Disclosure [Abstract]
Summary of Long-term Debt	Debt consisted of the following (in thousands): As of September 30, 2023 2022 2022 Term Loan due April 28, 2029 — SOFR + 2.50 % + 0.1% ( 7.92 % at September 30, 2023 and 4.09 % at September 30, 2022) $ 594,000 $ 600,000 Revolving Credit Facility through March 31, 2026 - SOFR + 0.1 % — — Total 594,000 600,000 Less unamortized deferred financing fees ( 3,996 ) ( 4,712 ) Less unamortized original issue discount ( 3,739 ) ( 4,409 ) Less current portion ( 6,000 ) ( 6,000 ) Long-term debt — less current portion and unamortized $ 580,265 $ 584,879
Schedule of Debt Payment	As of September 30, 2023, the Company scheduled fiscal year debt payment on the 2022 Term Loan Agreement as follows (in thousands): 2024 $ 6,000 2025 6,000 2026 6,000 2027 6,000 2028 6,000 Thereafter 564,000 Total $ 594,000
Summary of Interest Expense	Interest expense consisted of the following (in thousands): Years Ended September 30, 2023 2022 2021 Interest expense 2022 Term Loan Agreement $ 41,936 $ 10,640 $ — Term Loan Agreement — 8,824 17,826 Revolving Credit Facility 718 838 629 Other 4,484 3,661 828 Amortization Debt issue costs 2022 Term Loan Agreement 716 4,892 — Term Loan Agreement — 1,056 2,497 Revolving Credit Facility 262 262 495 Original issue discounts 2022 Term Loan Agreement 670 279 — Term Loan Agreement — 126 193 Less capitalized interest ( 5,211 ) ( 5,622 ) ( 2,157 ) Interest expense 43,575 24,956 20,311 Less interest income ( 4,282 ) — — Interest expense, net $ 39,293 $ 24,956 $ 20,311

Product Warranties (Tables)

Product Warranties (Tables)	12 Months Ended
Product Warranties (Tables)	Sep. 30, 2023
Product Warranties Disclosures [Abstract]
Summary of Warranty Reserve Activity	The warranty reserve activity was as follows (in thousands): As of September 30, 2023 2022 Beginning balance $ 15,023 $ 12,699 Adjustments to reserve 3,657 5,030 Warranty claims payment ( 2,485 ) ( 2,706 ) Ending balance 16,195 15,023 Current portion of accrued warranty ( 2,739 ) ( 2,900 ) Accrued warranty — less current portion $ 13,456 $ 12,123

Leases (Tables)

Leases (Tables)	12 Months Ended
Leases (Tables)	Sep. 30, 2023
Leases [Abstract]
Summary of Lease Assets and Lease Liabilities	Lease assets and lease liabilities as of September 30, 2023 and 2022 were as follows: As of September 30, Leases Classification on Balance Sheet 2023 2022 Assets ROU operating lease assets Other assets $ 15,423 $ 19,724 Finance lease assets Other assets 71,529 73,541 Total lease assets $ 86,952 $ 93,265 Liabilities Current Operating Accrued expenses and other liabilities $ 4,180 $ 5,223 Finance Accrued expenses and other liabilities 2,777 2,366 Non-Current Operating Other non-current liabilities 13,699 17,261 Finance Other non-current liabilities 75,718 75,706 Total lease liabilities $ 96,374 $ 100,556
Components of Lease Expense	The components of lease expense for the years ended September 30, 2023, 2022 and 2021 were as follows: Years Ended September 30, (in thousands) 2023 2022 2021 Operating lease expense $ 5,920 $ 5,669 $ 4,007 Finance lease amortization of assets 5,053 3,477 1,191 Finance lease interest on lease liabilities 4,391 3,616 827 Short term 392 574 133 Sublease income ( 293 ) ( 347 ) ( 428 ) Total lease expense $ 15,463 $ 12,989 $ 5,730
Cash Flows Related to Leases	Cash flows related to leases for the years ended September 30, 2023, 2022 and 2021 were as follows: Years Ended September 30, 2023 2022 2021 Cash paid for amounts included in the measurement of lease liabilities: Operating leases - Operating cash flows $ 6,171 $ 5,973 $ 4,096 Finance leases - Operating cash flows 4,391 3,617 827 Finance leases - Financing cash flows 2,619 249 1,921 Leased assets obtained in exchange for operating lease liabilities 3,041 5,487 10,239 Leased assets obtained in exchange for finance lease liabilities 789 27,438 47,578
Supplemental Information Related to Leases	The table below present supplemental information related to leases as of September 30, 2023 and 2022: As of September 30, 2023 2022 Weighted-average remaining lease term (years) Operating leases 6.8 6.9 Finance leases 25.4 26.5 Weighted-average discount rate Operating leases 4.4 % 4.1 % Finance leases 5.8 % 5.9 %
Summary of Maturities of Lease Liabilities	The table below reconciles the undiscounted cash flows for each of the first five years and the total of the remaining years to the finance lease liabilities and operating lease liabilities recorded on the balance sheet as of September 30, 2023: As of September 30, 2023 (in thousands) Operating Leases Finance Leases Total 2024 $ 4,856 $ 7,101 $ 11,957 2025 3,919 6,998 10,917 2026 2,594 6,835 9,429 2027 1,906 6,368 8,274 2028 1,642 5,265 6,907 Thereafter 6,070 117,013 123,083 Total lease payments 20,987 149,580 170,567 Less: Interest ( 3,108 ) ( 71,085 ) ( 74,193 ) Present Value of lease liability $ 17,879 $ 78,495 $ 96,374

Fair Value Of Financial Instr_2

Fair Value Of Financial Instruments (Tables)	12 Months Ended
Fair Value Of Financial Instruments (Tables)	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Summary of Carrying Values and the Estimated Fair Values of the Debt Financial Instruments	The carrying values and the estimated fair values of the debt financial instruments (Level 2 measurements) consisted of the following (in thousands): As of September 30, 2023 2022 Principle Outstanding Estimated Principle Outstanding Estimated 2022 Term Loan Agreement due April 28, 2029 $ 594,000 $ 595,485 $ 600,000 $ 586,500
Summary of Fair Values of Interest Rate Derivative Instruments as well as Classification on Balance Sheet	The following table provides the fair values of the interest rate derivative instruments as well as their classification on the Balance Sheet as of September 30, 2023 and 2022 (in thousands): Fair Value as of Fair Value Hierarchy Balance Sheet Location September 30, 2023 September 30, 2022 Assets Interest rate swaps Level 2 Other current assets $ 2,558 $ — Liabilities Interest rate swaps Level 2 Other non-current liabilities $ 65 $ —
Summary of Effects of Interest Rate Derivative Instruments	The following table summarizes the effects of the interest rate derivative instruments on Accumulated other comprehensive income (loss) as of September 30, 2023 (in thousands): Before-tax Amount Income Tax Expense Net of Tax Amount Balance - September 30, 2022 $ — $ — $ — Amount of gain recognized in other comprehensive income 3,474 870 2,604 Amount of gain reclassified from accumulated other comprehensive income (loss) into net income ( 981 ) ( 255 ) ( 726 ) Balance - September 30, 2023 $ 2,493 $ 615 $ 1,878

Segments (Tables)

Segments (Tables)	12 Months Ended
Segments (Tables)	Sep. 30, 2023
Segment Reporting [Abstract]
Summary of Residential and Commercial Segment Reporting Information	The segment data below includes data for Residential and Commercial for the years ended and as of September 30, 2023, 2022 and 2021 (in thousands). Years Ended and As of September 30, Residential Commercial Corporate and Total 2023 2022 2021 2023 2022 2021 2023 2022 2021 2023 2022 2021 Net Sales $ 1,222,866 $ 1,168,751 $ 1,044,126 $ 147,450 $ 186,835 $ 134,848 $ — $ — $ — $ 1,370,316 $ 1,355,586 $ 1,178,974 Adjusted EBITDA 329,853 323,377 314,563 31,008 40,255 19,323 ( 69,638 ) ( 62,592 ) ( 59,699 ) 291,223 301,040 274,187 Capital Expenditures 81,592 162,739 169,490 4,321 5,645 3,473 2,632 2,554 2,156 88,545 170,938 175,119 Depreciation and 119,466 105,421 88,732 8,789 9,332 9,127 4,289 3,780 3,745 132,544 118,533 101,604 Goodwill 953,882 953,606 911,001 40,389 40,389 40,389 — — — 994,271 993,995 951,390 Total Assets 2,150,994 2,173,069 1,953,126 192,865 186,824 200,277 21,695 23,198 34,431 2,365,554 2,383,091 2,187,834 Years Ended September 30, 2023 2022 2021 Segment Adjusted EBITDA Residential $ 329,853 $ 323,377 $ 314,563 Commercial 31,008 40,255 19,323 Total Adjusted EBITDA for reporting segments $ 360,861 $ 363,632 $ 333,886 Unallocated net expenses ( 69,638 ) ( 62,592 ) ( 59,699 ) Adjustments to income (loss) before income tax provision Depreciation and amortization ( 132,544 ) ( 118,533 ) ( 101,604 ) Stock-based compensation costs ( 18,704 ) ( 18,105 ) ( 22,670 ) Acquisition and divestiture costs (1) ( 6,890 ) ( 13,406 ) — Secondary offering costs ( 1,065 ) — ( 2,592 ) Inventories (2) — ( 19,297 ) — Other costs (3) ( 843 ) ( 2,764 ) ( 5,192 ) Interest expense, net ( 39,293 ) ( 24,956 ) ( 20,311 ) Income (loss) before income taxes $ 91,884 $ 103,979 $ 121,818 (1) Acquisition and divestiture costs reflect costs directly related to completed acquisitions of $ 3.9 million and $ 11.5 million for fiscal years 2023 and 2022, respectively, costs related to divestiture of $ 3.0 million and $ 0.5 million for fiscal year 2023 and 2022, respectively, and inventory step-up adjustments related to recording the inventory of acquired businesses at fair value on the date of acquisition of $ 1.4 million for fiscal years 2022. (2) During the fourth quarter of fiscal year 2022, the Company updated the process by which it estimates the value of its inventory. This included updating the assumptions that are used in determining and treating certain capitalized costs, primarily by incorporating the impacts of changes in the amount of recycled content introduced into its products. (3) Other costs reflect reduction in workforce costs of $ 0.5 million and $ 1.6 million for fiscal years 2023 and 2022, respectively, costs for legal expenses of $ 0.3 million, $ 0.9 million and $ 2.3 million for fiscal years 2023, 2022 and 2021, respectively, other costs of $ 0.2 million for fiscal year 2022, costs related to an incentive plan and other ancillary expenses associated with the initial public offering of $ 0.1 million and $ 2.4 million for fiscal years 2022 and 2021, respectively, and impact of the retroactive adoption of ASC 842 leases of $ 0.5 million for fiscal year 2021.

Capital Stock (Tables)

Capital Stock (Tables)	12 Months Ended
Capital Stock (Tables)	Sep. 30, 2023
Stockholders' Equity Note [Abstract]
Summery of Repurchases of Class A Common Stock	The table below summaries the Company's repurchases of its Class A common stock during the year ended September 30, 2023 and 2022 (in thousands, except per share amount): Year Ended September 30, 2023 2022 Total number of shares repurchased 4,152 4,117 Reacquisition cost (1), (2), (3) $ 116,579 $ 81,483 Average price per share $ 28.08 $ 19.79 (1) Reacquisition cost in the year ended September 30, 2023 includes the $ 36.0 million repurchase from the underwriter upon the completion of the secondary offering. The remaining repurchases in the year ended September 30, 2023 were made through open market transactions. (2) On August 16, 2022, the U.S. government enacted the Inflation Reduction Act of 2022 (the “Inflation Reduction Act”), that includes, among other provisions, a one percent excise tax on net repurchases of stock after December 31, 2022. As of September 30, 2023 , the Company recognized $ 1.1 million excise tax as reacquisition cost of share repurchases. (3) During the year ended September 30, 2022 , the Company repurchased $ 50.0 million of shares under an accelerated share repurchase agreement ("ASR") and $ 31.5 million of shares on the open market.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
Stock-Based Compensation (Tables)	Sep. 30, 2023
Service Based Stock Options And Restricted Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Summary of Share-Based Payment Award Valuation Assumptions	The following table sets forth the significant assumptions used for the service-based awards granted during the years ended September 30: 2023 2022 2021 Weighted average grant date fair value $ 9.02 $ 16.98 $ 12.49 Risk-free interest rate 3.77 % 1.34 % 0.56 %- 0.81 % Expected volatility 40.00 % 40.00 % 35.00 % Expected term (in years) 6.00 6.00 6.00 Expected dividend yield 0.00 % 0.00 % 0.00 %
Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Summary of Share-Based Compensation Stock Options Activity	The following table summarizes the performance-based stock option activity for the year ended September 30, 2023: Number of Weighted Weighted Aggregate (in years) (in thousands) Outstanding at October 1, 2022 1,410,653 $ 23.00 Granted — — Exercised ( 294,218 ) 23.00 Cancelled/Forfeited ( 2,174 ) 23.00 Outstanding at September 30, 2023 1,114,261 23.00 6.7 7,510 Vested and exercisable at September 30, 2023 1,114,261 $ 23.00 6.7 7,510
Service Based Stock Option Activity [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Summary of Share-Based Compensation Stock Options Activity	The following table summarizes the service-based stock option activity for the year ended September 30, 2023 : Number of Weighted Weighted Aggregate (in years) (in thousands) Outstanding at October 1, 2022 3,557,194 $ 25.57 Granted 250,477 20.18 Exercised ( 355,920 ) 23.00 Cancelled/Forfeited ( 90,044 ) 25.79 Outstanding at September 30, 2023 3,361,707 25.43 7.1 19,871 Vested and exercisable at September 30, 2023 2,400,930 $ 24.59 6.8 14,561
Performance Based Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Summary of Non-Vested Restricted Stock Activity	A summary of the performance-based restricted stock unit awards activity for the year ended September 30, 2023 was presented at target was as follows: Number of Weighted Outstanding and unvested at October 1, 2022 221,469 $ 37.55 Granted 319,263 20.18 Vested — — Forfeited ( 32,110 ) 35.09 Outstanding and unvested at September 30, 2023 508,622 $ 26.73
Service Based Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Summary of Non-Vested Restricted Stock Activity	A summary of the service-based restricted stock awards activity for the year ended September 30, 2023 was as follows: Number of Weighted Outstanding and unvested at October 1, 2022 275,628 $ 23.00 Granted — — Vested ( 173,841 ) 23.00 Forfeited ( 19,306 ) 23.00 Outstanding and unvested at September 30, 2023 82,481 $ 23.00
Schedule of Unvested Restricted Stock Units	A summary of the service-based restricted stock unit awards activity for the year ended September 30, 2023 was as follows: Number of Weighted Outstanding and unvested at October 1, 2022 574,499 $ 31.14 Granted 504,951 21.22 Vested ( 246,343 ) 29.74 Forfeited ( 47,011 ) 28.06 Outstanding and unvested at September 30, 2023 786,096 $ 25.39

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
Earnings Per Share (Tables)	Sep. 30, 2023
Earnings Per Share [Abstract]
Summary of Computation of Basic And Diluted Earnings Per Share	The following table sets forth the computation of the Company’s basic and diluted EPS attributable to common stockholders (in thousands, except share and per share amounts): Years Ended September 30, 2023 2022 2021 Numerator: Net income $ 67,955 $ 75,225 $ 93,150 Net income attributable to common $ 67,955 $ 75,225 $ 93,150 Denominator: Weighted average shares of common Basic 150,162,256 153,510,110 153,777,859 Diluted 150,849,896 154,517,843 156,666,394 Net income attributable to common Basic $ 0.45 $ 0.49 $ 0.61 Diluted $ 0.45 $ 0.49 $ 0.59
Summary of Antidilutive Securities Excluded From Computation of Earnings Per Share	The following table includes the number of shares that may be dilutive common shares in the future, and were not included in the computation of diluted net income (loss) per share because the effect was anti-dilutive: Years Ended September 30, 2023 2022 2021 Stock Options 2,549,816 548,539 105,199 Restricted Stock Units 113,622 268,526 3,256

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	The Company’s operations are substantially all domestic. The components of income tax expense (benefit) consisted of the following (in thousands): Years Ended September 30, 2023 2022 2021 Current: Federal $ 25,216 $ 810 $ 200 State and local 8,200 8,260 2,939 Total current 33,416 9,070 3,139 Deferred: Federal ( 6,828 ) 19,302 26,240 State and local ( 2,659 ) 382 ( 711 ) Total deferred ( 9,487 ) 19,684 25,529 Income tax expense $ 23,929 $ 28,754 $ 28,668
Schedule of Effective Income Tax Rate Reconciliation	The effective income tax rate was different from the statutory U.S. federal income tax rate of 21.0 %, for the years ended September 30, 2023, 2022 and 2021, due to the following (in thousands): 2023 Rate 2022 Rate 2021 Rate Income tax expense / federal statutory rate $ 19,296 21.0 % $ 21,836 21.0 % $ 25,583 21.0 % State and local taxes — net of federal expense 3,218 3.5 % 7,257 7.0 % 2,329 1.9 % Change in valuation allowance 597 0.6 % ( 350 ) ( 0.3 )% ( 220 ) ( 0.2 )% Stock-based compensation 721 0.8 % 145 0.1 % 1,379 1.1 % Non-deductible transaction costs — 0.0 % — 0.0 % 544 0.4 % Executive compensation 608 0.7 % 364 0.4 % 704 0.6 % Federal research and development credit ( 746 ) ( 0.8 )% ( 703 ) ( 0.7 )% ( 1,829 ) ( 1.4 )% Meals and entertainment 284 0.3 % 224 0.2 % 267 0.2 % Other ( 49 ) ( 0.1 )% ( 19 ) 0.0 % ( 89 ) ( 0.1 )% Income tax expense / effective tax rate $ 23,929 26.0 % $ 28,754 27.7 % $ 28,668 23.5 %
Schedule of Deferred Tax Assets and Liabilities	The components of the deferred tax assets and liabilities consisted of the following (in thousands): As of September 30, 2023 2022 Deferred tax asset: State loss carryforwards and other benefits $ 15,744 $ 13,699 Inventory reserves 14,203 13,852 Warranty reserves 4,148 3,839 Accrued expenses 11,996 10,607 Stock-based compensation 13,502 12,185 Lease liabilities 24,063 25,034 Valuation allowance ( 5,557 ) ( 4,960 ) Total deferred tax assets 78,099 74,256 Deferred tax liabilities: Intangible assets — net 37,272 42,197 Property, plant and equipment 74,611 73,471 Right-of-use assets 21,728 23,237 Unrealized gain in other comprehensive income 615 — Indemnification receivable related to warranty reserves 203 546 Total deferred tax liabilities 134,429 139,451 Net deferred tax liability $ 56,330 $ 65,195
Summary of Valuation Allowance	The activity in the valuation allowance consisted of the following (in thousands): As of September 30, 2023 2022 Beginning balance $ 4,960 $ 5,310 Expense 597 ( 350 ) Ending balance $ 5,557 $ 4,960
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the beginning and ending balances for liabilities associated with unrecognized tax benefits consisted of the following (in thousands): As of September 30, 2023 2022 Beginning balance $ 780 $ 955 Unrecognized tax benefits related to prior years 70 ( 230 ) Unrecognized tax benefits related to the current year 50 55 Ending balance $ 900 $ 780

Condensed Financial Informati_2

Condensed Financial Information of Registrant (Parent Company Only) (Tables) - Parent Company [Member]	12 Months Ended
	Sep. 30, 2023
Schedule of Balance Sheets	The AZEK Company Inc. (parent company only) Balance Sheets (In thousands of U.S. dollars, except for share and per share amounts) As of September 30, 2023 2022 ASSETS: Non-current assets: Investments in subsidiaries $ 1,429,643 $ 1,444,443 Total non-current assets 1,429,643 1,444,443 Total assets $ 1,429,643 $ 1,444,443 LIABILITIES AND STOCKHOLDERS’ EQUITY: Total liabilities $ — $ — Stockholders’ equity: Preferred stock, $ 0.001 par value; 1,000,000 shares authorized and no shares issued — — Class A common stock, $ 0.001 par value; 1,100,000,000 shares authorized, 155,967,736 shares issued at September 30, 2023, and 155,157,220 issued 156 155 Class B common stock, $ 0.001 par value; 100,000,000 shares authorized, 100 shares — — Additional paid-in capital 1,662,322 1,630,378 Accumulated deficit ( 45,047 ) ( 113,002 ) Accumulated other comprehensive income (loss) 1,878 — Treasury stock, at cost, 8,268,423 shares at September 30, 2023 and 4,116,570 shares at September 30, 2022 ( 189,666 ) ( 73,088 ) Total stockholders’ equity 1,429,643 1,444,443 Total liabilities and stockholders’ equity $ 1,429,643 $ 1,444,443
Schedule of Statements of Comprehensive Income	The AZEK Company Inc. (parent company only) Statements of Comprehensive Income (In thousands of U.S. dollars) Years Ended September 30, 2023 2022 2021 Net income of subsidiaries $ 67,955 $ 75,225 $ 93,150 Net income of subsidiaries $ 67,955 $ 75,225 $ 93,150 Comprehensive income $ 69,833 $ 75,225 $ 93,150

Organization and Summary of S_4

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) $ / shares in Units, $ in Thousands			3 Months Ended	12 Months Ended
	Jun. 01, 2021 USD ($) $ / shares shares	Jan. 26, 2021 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2023 USD ($) Customer Reportingunit $ / shares shares	Sep. 30, 2022 USD ($) Reportingunit Customer $ / shares shares	Sep. 30, 2021 USD ($) Reportingunit	Mar. 31, 2023 USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]
Total amount of incentives				$ 132,600	$ 105,800	$ 92,500
Advertising Expense				62,200	52,500	37,800
Research and development expenses				9,200	9,500	7,400
Gain (loss) on disposal of fixed assets				$ (200)	(500)	$ (1,000)
Lease term description				Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Leases may be classified as either operating leases or finance leases. We have made an accounting policy election to not include leases with an initial term of 12 months or less on the balance sheet.
Accumulated deficit				$ (45,047)	(113,002)
Lease asset				86,952	93,265
Lease liabilities				$ 96,374	$ 100,556
Contingent consideration			$ 5,800				$ 1,000
Qualitative Assessment [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of reporting units \| Reportingunit					5	3
Quantitative Assessment [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of reporting units \| Reportingunit				6	1	1
Minimum [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Intangible assets, useful lives				3 years
Maximum [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Intangible assets, useful lives				20 years
Accounts Receivable [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Customers accounted				one customer represented 17.2% of gross trade receivables.	two customers each represented more than 10% of gross trade receivables: Customer A was 10.6% and Customer B was 14.8%.
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| One Customer [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage				17.20%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Customer A [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage					10.60%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| CustomerBMember
Organization And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage					14.80%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Minimum [Member] \| Two Customer [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage					10%
Accounts Receivable [Member] \| Supplier Concentration Risk [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of Customer \| Customer				1	2
Cost of Goods and Service Benchmark [Member] \| Supplier Concentration Risk [Member] \| Raw Materials [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage				17%	16%	18%
Residential Segment [Member] \| Sales Revenue Net [Member] \| Customer Concentration Risk [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage				10%	10%	10%
Common Class A [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Number of shares repurchased \| shares				4,152,000	4,117,000
Common stock, par value per share \| $ / shares				$ 0.001	$ 0.001
Stock repurchased during period, value				$ 116,579	$ 81,483
Common Class B [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Common stock, par value per share \| $ / shares				$ 0.001	$ 0.001
Over-Allotment Option [Member] \| Common Class A [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Overallotment stock shares sold by shareholders during the period \| shares	2,250,000	3,000,000	2,100,000
Over-Allotment Option [Member] \| Common Class A [Member] \| Maximum [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Overallotment stock shares sold by shareholders during the period \| shares			2,100,000
Secondary Offerings [Member] \| Common Class A [Member]
Organization And Summary Of Significant Accounting Policies [Line Items]
Stock shares sold by shareholders during the period \| shares	17,250,000	23,000,000	16,100,000
Number of shares repurchased \| shares			1,477,832	1,477,832
Common stock, par value per share \| $ / shares	$ 0.001	$ 0.001	$ 0.001
Estimated offering expenses	$ 1,100	$ 1,200	$ 1,100
Sales price per share \| $ / shares	$ 43.50	$ 40	$ 24.36
Stock repurchased during period, value			$ 36,000	$ 36,000
Selling Stockholders, aggregate purchase price				$ 36,000

Organization and Summary of S_5

Organization and Summary of Significant Accounting Policies - Schedules of Concentration of Risk Percentage (Detail)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Revenue Benchmark [Member] \| Customer Concentration Risk [Member] \| Distributor A [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	18.70%	19.30%	23.30%

Organization and Summary of S_6

Organization and Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Property, Plant and Equipment (Detail)	Sep. 30, 2023
Land and Improvements [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, estimated useful lives	10 years
Vehicles [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, estimated useful lives	5 years
Minimum [Member] \| Buildings and Improvements [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, estimated useful lives	7 years
Minimum [Member] \| Manufacturing Equipment [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, estimated useful lives	1 year
Minimum [Member] \| Office Furniture And Equipment [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, estimated useful lives	3 years
Minimum [Member] \| Computer Equipment [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, estimated useful lives	3 years
Maximum [Member] \| Buildings and Improvements [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, estimated useful lives	40 years
Maximum [Member] \| Manufacturing Equipment [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, estimated useful lives	15 years
Maximum [Member] \| Office Furniture And Equipment [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, estimated useful lives	12 years
Maximum [Member] \| Computer Equipment [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, estimated useful lives	7 years

Revenue - Additional Informatio

Revenue - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Accrued rebates	$ 60,974	$ 50,479	$ 44,300
Contra trade receivable	$ 6,000	$ 6,100	$ 3,300

Revenue - Summary of Rebate Act

Revenue - Summary of Rebate Activity (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Revenue from Contract with Customer [Abstract]
Beginning balance	$ 56,542	$ 47,648	$ 32,679
Rebate expense	106,762	88,057	76,763
Rebate payments	(96,346)	(79,163)	(61,794)
Ending balance	$ 66,958	$ 56,542	$ 47,648

Inventories - Schedule of Inven

Inventories - Schedule of Inventories (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Inventory Disclosure [Abstract]
Raw materials	$ 67,330	$ 72,464
Work in process	37,038	39,829
Finished goods	116,733	187,612
Total inventories	$ 221,101	$ 299,905

Property, Plant and Equipment_3

Property, Plant and Equipment - Net - Summary of Property, Plant and Equipment - Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Property, Plant and Equipment [Abstract]
Land and improvements	$ 4,829	$ 3,350
Buildings and improvements	129,031	110,300
Manufacturing equipment	624,754	540,536
Computer equipment	32,300	28,198
Furnitures and fixtures	7,290	6,867
Vehicles	1,105	941
Property Plant and Equipment Excluding Construction in Progress Gross	799,309	690,192
Construction in progress	94,422	140,566
Property, Plant and Equipment, Gross	893,731	830,758
Accumulated depreciation	(392,708)	(312,845)
Total property, plant and equipment – net	$ 501,023	$ 517,913

Property, Plant and Equipment_4

Property, Plant and Equipment - Net - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
Depreciation	$ 81.2	$ 64.5	$ 50.6
Interest Capitalized	$ 5.2	$ 5.6	$ 2.2

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Net - Summary of Changes in Carrying Amount of Goodwill (Detail) $ in Thousands	12 Months Ended
	Sep. 30, 2023 USD ($)
Goodwill [Line Items]
Goodwill before impairment, beginning balance	$ 1,026,195
Accumulated impairment losses, beginning balance	(32,200)
Goodwill net, beginning balance	993,995
Acquisitions	276
Goodwill before impairment, ending balance	1,026,471
Accumulated impairment losses, ending balance	(32,200)
Goodwill net, ending balance	994,271
Residential [Member]
Goodwill [Line Items]
Goodwill before impairment, beginning balance	953,606
Goodwill net, beginning balance	953,606
Acquisitions	276
Goodwill before impairment, ending balance	953,882
Goodwill net, ending balance	953,882
Commercial [Member]
Goodwill [Line Items]
Goodwill before impairment, beginning balance	72,589
Accumulated impairment losses, beginning balance	(32,200)
Goodwill net, beginning balance	40,389
Acquisitions	0
Goodwill before impairment, ending balance	72,589
Accumulated impairment losses, ending balance	(32,200)
Goodwill net, ending balance	$ 40,389

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Net - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Indefinite lived intangible assets other than goodwill	$ 0	$ 0
Amortization expense	$ 46,338,000	$ 50,537,000	$ 49,802,000
Remaining weighted-average amortization period for acquired intangible assets	11 years 2 months 12 days

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Net - Summary of Finite-Lived Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 720,068	$ 720,068
Accumulated Amortization	(520,571)	(474,233)
Net Carrying Value	199,497	245,835
Propriety Knowledge [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	300,400	300,400
Accumulated Amortization	(253,608)	(236,024)
Net Carrying Value	46,792	64,376
Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	230,240	230,240
Accumulated Amortization	(164,759)	(151,259)
Net Carrying Value	65,481	78,981
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	176,852	176,852
Accumulated Amortization	(92,268)	(78,015)
Net Carrying Value	84,584	98,837
Patents [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	8,500	8,500
Accumulated Amortization	(5,913)	(4,950)
Net Carrying Value	2,587	3,550
Other intangible [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	4,076	4,076
Accumulated Amortization	(4,023)	(3,985)
Net Carrying Value	$ 53	$ 91
Minimum [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	3 years
Minimum [Member] \| Propriety Knowledge [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	10 years	10 years
Minimum [Member] \| Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	5 years	5 years
Minimum [Member] \| Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	12 years	12 years
Minimum [Member] \| Patents [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	9 years	9 years
Minimum [Member] \| Other intangible [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	3 years	3 years
Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	20 years
Maximum [Member] \| Propriety Knowledge [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	15 years	15 years
Maximum [Member] \| Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	20 years	20 years
Maximum [Member] \| Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	19 years	19 years
Maximum [Member] \| Patents [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	10 years	10 years
Maximum [Member] \| Other intangible [Member]
Finite Lived Intangible Assets [Line Items]
Acquired finite lived intangible asset useful life	15 years	15 years

Goodwill and Intangible Asset_6

Goodwill and Intangible Assets - Net - Summary of Expected Amortization Expense Relating to Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2024	$ 40,748
2025	35,204
2026	29,660
2027	24,115
2028	18,572
Thereafter	51,198
Net Carrying Value	$ 199,497	$ 245,835

Composition of Certain Balanc_3

Composition of Certain Balance Sheet Accounts - Summary of Allowance for Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Allowance for Credit Loss [Abstract]
Beginning balance	$ 1,397	$ 1,109	$ 1,332
Provision	731	290	342
Bad debt write-offs	(355)	(2)	(565)
Ending balance	$ 1,773	$ 1,397	$ 1,109

Composition of Certain Balanc_4

Composition of Certain Balance Sheet Accounts - Summary of Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Accrued Liabilities and Other Liabilities [Abstract]
Employee related liabilities	$ 34,313	$ 36,866
Taxes	6,959	142
Lease liability operating	4,180	5,223
Customer deposits	4,152	2,494
Marketing	3,868	4,272
Construction in progress	2,863	9,032
Lease liability finance	$ 2,777	$ 2,366
Finance Lease Liability Current Statement Of Financial Position [Extensible List]	Total accrued expenses and other current liabilities	Total accrued expenses and other current liabilities
Warranty	$ 2,739	$ 2,900
Utilities	2,141	794
Professional fees	2,073	2,089
Freight	1,242	1,821
Commissions	991	1,032
Other	3,696	3,558
Total accrued expenses and other current liabilities	$ 71,994	$ 72,589

Debt - Summary of Long-Term Deb

Debt - Summary of Long-Term Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 594,000	$ 600,000
Less unamortized deferred financing fees	(3,996)	(4,712)
Less unamortized original issue discount	(3,739)	(4,409)
Less current portion	(6,000)	(6,000)
Long-term debt — less current portion and unamortized financing fees	580,265	584,879
2022 Term Loan [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	594,000	600,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Less unamortized deferred financing fees	$ (700)	$ (900)

Debt - Summary of Long-Term D_2

Debt - Summary of Long-Term Debt (Detail) (Parenthetical)		12 Months Ended
Debt - Summary of Long-Term Debt (Detail) (Parenthetical)	Apr. 28, 2022	Sep. 30, 2023	Sep. 30, 2022
2022 Term Loan Agreement
Debt Instrument [Line Items]
Debt instrument maturity date	Apr. 28, 2029	Apr. 28, 2029
Debt instrument, description of variable rate basis		SOFR + 2.50% + 0.1%	SOFR + 2.50% + 0.1%
Debt instrument, basis spread on variable rate		2.50%	2.50%
Debt instrument rate		7.92%	4.09%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument maturity date		Mar. 31, 2026
Debt instrument, description of variable rate basis		SOFR + 0.1%	SOFR + 0.1%
Debt instrument, basis spread on variable rate		0.10%	0.10%

Debt - Schedule of Debt Payment

Debt - Schedule of Debt Payment (Detail) $ in Thousands	Sep. 30, 2023 USD ($)
Debt Disclosure [Abstract]
2024	$ 6,000
2025	6,000
2026	6,000
2027	6,000
2028	6,000
Thereafter	564,000
Total	$ 594,000

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)			12 Months Ended
Debt - Additional Information (Detail) - USD ($)	Jan. 26, 2023	Apr. 28, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Debt Instrument [Line Items]
Long-term Debt, Gross			$ 594,000,000	$ 600,000,000
Deferred financing cost			3,996,000	4,712,000
Interest expense			43,575,000	24,956,000	$ 20,311,000
Accrued interest paid			$ 41,728,000	14,899,000	17,119,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument maturity date			Mar. 31, 2026
Deferred financing cost			$ 700,000	$ 900,000
Debt instrument, basis spread on variable rate			0.10%	0.10%
Aggregate maximum borrowing capacity			$ 150,000,000
Outstanding letters of credit			2,800,000	$ 2,800,000
Option to increase line of credit facility borrowing capacity			$ 100,000,000
Debt instrument interest rate description			interest rate has been reduced by 25 basis points to (i) for ABR borrowings, the highest of (a) the Federal Funds Rate plus 50 basis points, (b) the prime rate and (c) the LIBOR as of such date for a deposit in U.S. dollars with a maturity of one month plus 100 basis points, plus, in each case, a spread of 25 to 75 basis points, based on average historical availability, or (ii) for Eurocurrency borrowings, adjusted LIBOR plus a spread of 125 to 175 basis points, based on average historical availability.
Debt instrument, description of variable rate basis			SOFR + 0.1%	SOFR + 0.1%
Line of credit facility, commitment fee description			If the average daily used percentage is greater than 50%, the commitment fee equals 25 basis points, and if the average daily used percentage is less than or equal to 50%, the commitment fee equals 37.5 basis points.
Line of credit facility, commitment fee amount			$ 600,000	$ 500,000	600,000
Debt instrument, covenant description			(i) 10% of the lesser of the aggregate commitments under the Revolving Credit Facility and the borrowing base, and (ii) $12.5 million
Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument maturity date			Mar. 31, 2026
Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument maturity date			May 09, 2022
Revolving Credit Facility [Member] \| The AZEK Group LLC
Debt Instrument [Line Items]
Revolving Credit Facility, outstanding amount			$ 0	0
Available borrowing capacity			$ 147,200,000
Debt instrument, covenant description			The AZEK Group LLC is also required to make mandatory prepayments (i) when aggregate borrowings exceed commitments or the applicable borrowing base and (ii) during “cash dominion,” which occurs if (a) the availability under the Revolving Credit Facility is less than the greater of (i) $12.5 million and (ii) 10% of the lesser of (x) $150.0 million and (y) the borrowing base, for five consecutive business days or (b) certain events of default have occurred and are continuing.
Revolving Credit Facility [Member] \| The AZEK Group LLC \| Maximum [Member]
Debt Instrument [Line Items]
Maximum fixed charge coverage ratio			100
Revolving Credit Facility [Member] \| The AZEK Group LLC \| Minimum [Member]
Debt Instrument [Line Items]
Minimum fixed charge coverage ratio			100
Revolving Credit Facility [Member] \| Abr Borrowings
Debt Instrument [Line Items]
Debt instrument interest rate description			(i) for ABR borrowings, the highest of (a) the Federal Funds Rate plus 50 basis points, (b) the prime rate and (c) the LIBOR as of such date for a deposit in U.S. dollars with a maturity of one month plus 100 basis points, plus, in each case, a spread of 25 to 75 basis points, based on average historical availability
Revolving Credit Facility [Member] \| Eurocurrency Borrowings [Member]
Debt Instrument [Line Items]
Debt instrument interest rate description			for Eurocurrency borrowings, adjusted LIBOR plus a spread of 125 to 175 basis points, based on average historical availability
Amended Agreement For Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Deferred financing cost			$ 500,000
Interest expense					$ 100,000
Lender fees			$ 900,000
Federal Funds Rate \| Revolving Credit Facility [Member] \| Abr Borrowings
Debt Instrument [Line Items]
Debt instrument, description of variable rate basis			Federal Funds Rate plus 50 basis points
Team SOFR \| Revolving Credit Facility [Member] \| The AZEK Group LLC
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.10%
Prime Rate [Member] \| Revolving Credit Facility [Member] \| Abr Borrowings
Debt Instrument [Line Items]
Debt instrument, description of variable rate basis			prime rate
London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Abr Borrowings
Debt Instrument [Line Items]
Debt instrument, description of variable rate basis			LIBOR as of such date for a deposit in U.S. dollars with a maturity of one month plus 100 basis points, plus, in each case, a spread of 25 to 75 basis points
London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Eurocurrency Borrowings [Member]
Debt Instrument [Line Items]
Debt instrument, description of variable rate basis			LIBOR plus a spread of 125 to 175 basis points
2022 Term Loan Agreement
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 600,000,000	$ 594,000,000	600,000,000
Debt instrument maturity date		Apr. 28, 2029	Apr. 28, 2029
Deferred financing cost			$ 4,000,000	$ 4,700,000
Percentage of principal amount to be repaid by way of instalments		0.25%
Debt instrument, basis spread on variable rate			2.50%	2.50%
Interest expense				$ 5,100,000
Lender fees				4,500,000
Remaining unamortized debt discount and debt issuance costs				1,800,000
Write-off of unamortized debt discount and debt issuance costs				500,000
Third-party costs of debt modification				$ 4,600,000
Debt instrument, description of variable rate basis			SOFR + 2.50% + 0.1%	SOFR + 2.50% + 0.1%
2022 Term Loan Agreement \| Interest Expense
Debt Instrument [Line Items]
Third party costs related to term loan amendment				$ 3,400,000
2022 Term Loan Agreement \| Federal Funds Rate \| Abr Borrowings
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.50%
2022 Term Loan Agreement \| Team SOFR \| Abr Borrowings
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1%
Applicable margin rate		1.50%
2022 Term Loan Agreement \| Team SOFR \| SOFR Borrowings [Member]
Debt Instrument [Line Items]
Applicable margin rate		2.50%
2022 Term Loan Agreement \| Alternative Base Rate \| Abr Borrowings
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.50%

Debt - Summary of Interest Expe

Debt - Summary of Interest Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Interest expense
Other	$ 4,484	$ 3,661	$ 828
Original issue discounts
Less capitalized interest	(5,211)	(5,622)	(2,157)
Interest expense	43,575	24,956	20,311
Less interest income	(4,282)	0
Interest expense, net	39,293	24,956	20,311
2022 Term Loan Agreement
Interest expense
Interest Expense, debt	41,936	10,640
Amortization - Debt issue costs
Amortization of debt issuance costs	716	4,892
Original issue discounts
Original issue discounts	670	279
Interest expense		5,100
Term Loan
Interest expense
Interest Expense, debt		8,824	17,826
Amortization - Debt issue costs
Amortization of debt issuance costs		1,056	2,497
Original issue discounts
Original issue discounts		126	193
Revolving Credit Facility [Member]
Interest expense
Interest Expense, debt	718	838	629
Amortization - Debt issue costs
Amortization of debt issuance costs	$ 262	$ 262	$ 495

Product Warranties - Additional

Product Warranties - Additional Information (Detail)	12 Months Ended
Product Warranties - Additional Information (Detail)	Sep. 30, 2023
Product Warranties Disclosures [Abstract]
Assurance of product	The Company provides product assurance warranties of various lengths ranging from 5 years to lifetime for limited coverage for a variety of material and workmanship defects based on standard terms and conditions between the Company and its customers.

Product Warranties - Summary of

Product Warranties - Summary of Warranty Reserve Activity (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Product Warranties Disclosures [Abstract]
Beginning balance	$ 15,023	$ 12,699
Adjustments to reserve	3,657	5,030
Warranty claims payment	(2,485)	(2,706)
Ending balance	16,195	15,023
Current portion of accrued warranty	(2,739)	(2,900)
Accrued warranty — less current portion	$ 13,456	$ 12,123

Leases - Additional Information

Leases - Additional Information (Detail)	12 Months Ended
Leases - Additional Information (Detail)	Sep. 30, 2023
Minimum [Member]
Lessee Lease Description [Line Items]
Renewal options range	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Renewal options range	20 years

Leases - Summary of Lease Asset

Leases - Summary of Lease Assets and Lease Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Assets
ROU operating lease assets	$ 15,423	$ 19,724
Operating Lease Right Of Use Asset Statement Of Financial Position Extensible List	Other assets	Other assets
Finance lease assets	$ 71,529	$ 73,541
Finance Lease Right Of Use Asset Statement Of Financial Position Extensible List	Other assets	Other assets
Total lease assets	$ 86,952	$ 93,265
Current liabilities
Operating	$ 4,180	$ 5,223
Operating Lease Liability Current Statement Of Financial Position Extensible List	Accrued expenses and other liabilities	Accrued expenses and other liabilities
Finance	$ 2,777	$ 2,366
Finance Lease Liability Current Statement Of Financial Position Extensible List	Accrued Liabilities and Other Liabilities	Accrued Liabilities and Other Liabilities
Non-Current liabilities
Operating	$ 13,699	$ 17,261
Operating Lease Liability Noncurrent Statement Of Financial Position Extensible List	Other non-current liabilities	Other non-current liabilities
Finance	$ 75,718	$ 75,706
Finance Lease Liability Noncurrent Statement Of Financial Position Extensible List	Other non-current liabilities	Other non-current liabilities
Total lease liabilities	$ 96,374	$ 100,556

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Leases [Abstract]
Operating lease expense	$ 5,920	$ 5,669	$ 4,007
Finance lease amortization of assets	5,053	3,477	1,191
Finance lease interest on lease liabilities	4,391	3,616	827
Short term	392	574	133
Sublease income	(293)	(347)	(428)
Total lease expense	$ 15,463	$ 12,989	$ 5,730

Leases - Cash Flows Related to

Leases - Cash Flows Related to Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Leases [Abstract]
Operating leases - Operating cash flows	$ 6,171	$ 5,973	$ 4,096
Finance leases - Operating cash flows	4,391	3,617	827
Finance leases - Financing cash flows	2,619	249	1,921
Leased assets obtained in exchange for operating lease liabilities	3,041	5,487	10,239
Leased assets obtained in exchange for finance lease liabilities	$ 789	$ 27,438	$ 47,578

Leases - Supplemental Informati

Leases - Supplemental Information related to Lease (Detail)	Sep. 30, 2023	Sep. 30, 2022
Weighted-average remaining lease term (years)
Operating leases	6 years 9 months 18 days	6 years 10 months 24 days
Finance leases	25 years 4 months 24 days	26 years 6 months
Weighted-average discount rate
Operating leases	4.40%	4.10%
Finance leases	5.80%	5.90%

Leases - Summary of Maturities

Leases - Summary of Maturities of Lease Liabilities (Detail) $ in Thousands	Sep. 30, 2023 USD ($)
Operating Leases
2024	$ 4,856
2025	3,919
2026	2,594
2027	1,906
2028	1,642
Thereafter	6,070
Total lease payments	20,987
Less: Interest	(3,108)
Present Value of lease liability	17,879
Finance Leases
2024	7,101
2025	6,998
2026	6,835
2027	6,368
2028	5,265
Thereafter	117,013
Total lease payments	149,580
Less: Interest	(71,085)
Present Value of lease liability	78,495
Total
2024	11,957
2025	10,917
2026	9,429
2027	8,274
2028	6,907
Thereafter	123,083
Total lease payments	170,567
Less: Interest	(74,193)
Present Value of lease liability	$ 96,374

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Carrying Values and the Estimated Fair Values of the Debt Financial Instruments (Detail) - 2022 Term Loan Agreement due April 28, 2029 [Member] - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Schedule of carrying values and the estimated fair values of the debt financial instruments [Line Items]
Debt instrument maturity date	Apr. 28, 2029
Carrying Value [Member] \| Fair Value, Inputs, Level 2 [Member]
Schedule of carrying values and the estimated fair values of the debt financial instruments [Line Items]
Loans payable	$ 594,000	$ 600,000
Estimated Fair Value [Member] \| Fair Value, Inputs, Level 2 [Member]
Schedule of carrying values and the estimated fair values of the debt financial instruments [Line Items]
Loans payable	$ 595,485	$ 586,500

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Additional Information (Detail) $ in Millions		12 Months Ended
	Aug. 01, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Apr. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Nov. 30, 2022 USD ($) Agreement	Dec. 29, 2021 USD ($)
StruXure Outdoor, LLC [Member]
Fair Value Of Financial Instruments [Line Items]
Contingent payment arrangements, range of outcomes, value, low		$ 0
Contingent payment arrangements, range of outcomes, value, high		13.9
Contingent consideration					$ 12.7			$ 9.5
Contingent liability				$ 12.7
Contingent payment compensation expense		3.2	$ 9.5
INTEX Millwork Solutions, LLC
Fair Value Of Financial Instruments [Line Items]
Contingent payment arrangements, range of outcomes, value, low	$ 0
Contingent payment arrangements, range of outcomes, value, high	6.2
Contingent consideration	$ 5.8					$ 6.2
Contingent liability		6.2
Date of acquisition	Aug. 01, 2022
INTEX Millwork Solutions, LLC \| Selling, General and Administrative Expense [Member]
Fair Value Of Financial Instruments [Line Items]
Fair value adjustment for contingent consideration		$ 0.4
Derivatives [Member]
Fair Value Of Financial Instruments [Line Items]
Number of interest rate swap agreements \| Agreement							2
Derivative, notional amount							$ 150
Derivative, maturity date		Oct. 31, 2025
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months, before tax		$ 2.6
Interest rate cash flow hedge gain (loss) to be reclassified during next 12 months, after tax		$ 1.9
Derivatives [Member] \| Interest Rate Swap 2 [Member]
Fair Value Of Financial Instruments [Line Items]
Derivative, fixed interest rate							4.39%
Derivatives [Member] \| Interest Rate Swap 1 [Member]
Fair Value Of Financial Instruments [Line Items]
Derivative, fixed interest rate							4.48%

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Summary of Fair Values of Interest Rate Derivative Instruments as well as Classification on the Balance Sheet (Detail) - Fair Value, Inputs, Level 2 [Member] $ in Thousands	Sep. 30, 2023 USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps	$ 2,558
Interest rate swaps	$ 65

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Summary of Effects of Interest Rate Derivative Instruments (Detail) $ in Thousands	12 Months Ended
	Sep. 30, 2023 USD ($)
Effect Of Cash Flow Hedge Accounting On AOCI [Line Items]
Amount of gain recognized in other comprehensive income, Before-tax amount	$ 3,474
Amount of gain recognized in other comprehensive income, Income tax expense	870
Amount of gain recognized in other comprehensive income, Net of tax amount	2,604
Amount of gain reclassified from accumulated other comprehensive income (loss) into net income, Before-tax amount	(981)
Amount of gain reclassified from accumulated other comprehensive income (loss) into net income, Income tax expense	(255)
Amount of gain reclassified from accumulated other comprehensive income (loss) into net income, Net of tax amount	(726)
Balance, Before-tax amount	2,493
Balance, Income tax expense	615
Balance, Net of tax amount	$ 1,878

Segment - Additional Informatio

Segment - Additional Information (Detail)	12 Months Ended
Segment - Additional Information (Detail)	Sep. 30, 2023 Segment
Segment Reporting [Abstract]
Number of Reportable Segments	2

Segments - Summary of Residenti

Segments - Summary of Residential and Commercial Segment Reporting Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Net Sales	$ 1,370,316	$ 1,355,586	$ 1,178,974
Segment Adjusted EBITDA
Total Adjusted EBITDA for reporting segments	291,223	301,040	274,187
Unallocated net expenses	(69,638)	(62,592)	(59,699)
Adjustments to Income (loss) before income tax provision (benefit)
Capital Expenditures	88,545	170,938	175,119
Depreciation and amortization	(132,544)	(118,533)	(101,604)
Goodwill	994,271	993,995	951,390
Total Assets	2,365,554	2,383,091	2,187,834
Stock-based compensation costs	(18,704)	(18,105)	(22,670)
Acquisition and divestiture costs	(6,890)	(13,406)
Secondary offering costs	(1,065)		(2,592)
Inventories		(19,297)
Other costs	(843)	(2,764)	(5,192)
Interest expense, net	39,293	24,956	20,311
Income (loss) before income taxes	91,884	103,979	121,818
Reportable Subsegments [Member]
Segment Adjusted EBITDA
Total Adjusted EBITDA for reporting segments	360,861	363,632	333,886
Corporate and Eliminations [Member]
Segment Adjusted EBITDA
Total Adjusted EBITDA for reporting segments	(69,638)	(62,592)	(59,699)
Adjustments to Income (loss) before income tax provision (benefit)
Capital Expenditures	2,632	2,554	2,156
Depreciation and amortization	(4,289)	(3,780)	(3,745)
Total Assets	21,695	23,198	34,431
Residential [Member]
Segment Reporting Information [Line Items]
Net Sales	1,222,866	1,168,751	1,044,126
Segment Adjusted EBITDA
Total Adjusted EBITDA for reporting segments	329,853	323,377	314,563
Adjustments to Income (loss) before income tax provision (benefit)
Capital Expenditures	81,592	162,739	169,490
Depreciation and amortization	(119,466)	(105,421)	(88,732)
Goodwill	953,882	953,606	911,001
Total Assets	2,150,994	2,173,069	1,953,126
Commercial [Member]
Segment Reporting Information [Line Items]
Net Sales	147,450	186,835	134,848
Segment Adjusted EBITDA
Total Adjusted EBITDA for reporting segments	31,008	40,255	19,323
Adjustments to Income (loss) before income tax provision (benefit)
Capital Expenditures	4,321	5,645	3,473
Depreciation and amortization	(8,789)	(9,332)	(9,127)
Goodwill	40,389	40,389	40,389
Total Assets	$ 192,865	$ 186,824	$ 200,277

Segments - Summary of Residen_2

Segments - Summary of Residential and Commercial Segment Reporting Information (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Business Transformation Costs [Line Items]
Business acquisition acquisition costs completed acquisitions	$ 3.9	$ 11.5
Divestiture costs	3	0.5
Inventory step up adjustments relating to business acquisitions		1.4
Costs of reduction in workforce	0.5	1.6
Legal expenses	$ 0.3	0.9	$ 2.3
Other costs, other		0.2
Lease impact			0.5
IPO [Member]
Business Transformation Costs [Line Items]
Costs related to an incentive plan		$ 0.1	$ 2.4

Capital Stock - Additional Info

Capital Stock - Additional Information (Detail) - USD ($)			3 Months Ended	12 Months Ended
Capital Stock - Additional Information (Detail) - USD ($)	Jun. 01, 2021	Jan. 26, 2021	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	May 05, 2022
Class Of Stock [Line Items]
Number of shares available for repurchase				$ 201,900,000
Common Class A [Member]
Class Of Stock [Line Items]
Number of shares repurchased				4,152,000	4,117,000
Common stock, par value per share				$ 0.001	$ 0.001
Average price per share				$ 28.08	$ 19.79
Common stock, shares outstanding				147,699,313
Common stock, shares issued				155,967,736	155,157,220
Shares issued excludes treasury stocks				147,699,313
Common Class A [Member] \| Over-Allotment Option [Member]
Class Of Stock [Line Items]
Overallotment stock shares sold by shareholders during the period	2,250,000	3,000,000	2,100,000
Common Class A [Member] \| Secondary Offerings [Member]
Class Of Stock [Line Items]
Stock shares sold by shareholders during the period	17,250,000	23,000,000	16,100,000
Number of shares repurchased			1,477,832	1,477,832
Common stock, par value per share	$ 0.001	$ 0.001	$ 0.001
Sales price per share	$ 43.50	$ 40	$ 24.36
Estimated offering expenses	$ 1,100,000	$ 1,200,000	$ 1,100,000
Average price per share				$ 24.36
Selling Stockholders, aggregate purchase price				$ 36,000,000
Common Class A [Member] \| Maximum [Member]
Class Of Stock [Line Items]
Stock repurchase program, authorized amount						$ 400,000,000
Common Class A [Member] \| Maximum [Member] \| Over-Allotment Option [Member]
Class Of Stock [Line Items]
Overallotment stock shares sold by shareholders during the period			2,100,000
Common Class B [Member]
Class Of Stock [Line Items]
Common stock, par value per share				$ 0.001	$ 0.001
Common stock, shares outstanding				100	100
Common stock, shares issued				100	100

Capital Stock - Summery of Repu

Capital Stock - Summery of Repurchases of Class A Common Stock (Details) - Common Class A [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Class of Stock [Line Items]
Total number of shares repurchased	4,152	4,117
Reacquisition cost	$ 116,579	$ 81,483
Average price per share	$ 28.08	$ 19.79

Capital Stock - Summery of Re_2

Capital Stock - Summery of Repurchases of Class A Common Stock (Parenthetical) (Details) - Common Class A [Member] - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022
Class of Stock [Line Items]
Reacquisition cost		$ 116,579	$ 81,483
Excise tax as reacquisition cost of share repurchases		1,100
Accelerated Share Repurchase Agreement [Member]
Class of Stock [Line Items]
Reacquisition cost			50,000
Open Market [Member]
Class of Stock [Line Items]
Reacquisition cost			$ 31,500
Secondary Offerings [Member]
Class of Stock [Line Items]
Reacquisition cost	$ 36,000	$ 36,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expenses	$ 18,704	$ 18,105	$ 22,670
Income tax benefit stock based compensation expenses	3,600	4,100	3,800
Unvested stock compensation not recognised	$ 23,500
Unvested stock awards weighted average remaining period of recognition	1 year 7 months 6 days
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of stock options exercised	$ 3,500	3,000	4,200
Tax benefit (expense) from stock options exercised	2,000	700	(1,900)
Service Based Restricted Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total fair value of vested restricted stock awards/units	2,600	4,200	2,700
Service Based Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total fair value of vested restricted stock awards/units	7,300	2,300	400
Selling, General and Administrative Expenses [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expenses	$ 18,700	$ 18,100	22,700
2020 Omnibus Incentive Compensation Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum number of shares authorised under share based compensation plan	15,852,319
Common stock shares reserved for future issuance	2,759,532
Stock based compensation period of expiry of stock options	10 years
CFOs Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expenses			$ 8,800

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Share-Based Payment Award Valuation Assumptions (Detail) - Service Based Stock Options [Member] - $ / shares	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value	$ 9.02	$ 16.98	$ 12.49
Risk-free interest rate	3.77%	1.34%
Expected volatility	40%	40%	35%
Expected term (in years)	6 years	6 years	6 years
Expected dividend yield	0%	0%	0%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate			0.56%
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate			0.81%

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Option Activities (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Sep. 30, 2023 USD ($) $ / shares shares
Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Option, Outstanding \| shares	1,410,653
Number of Option, Granted \| shares	0
Number of Option, Exercised \| shares	(294,218)
Number of Option, Cancelled/Forfeited \| shares	(2,174)
Number of Option, Outstanding \| shares	1,114,261
Number of Option, Vested and exercisable \| shares	1,114,261
Weighted Average Exercise Price Per Share, Outstanding \| $ / shares	$ 23
Weighted Average Exercise Price Per Share, Granted \| $ / shares	0
Weighted Average Exercise Price Per Share, Exercised \| $ / shares	23
Weighted Average Exercise Price Per Share, Cancelled/Forfeited \| $ / shares	23
Weighted Average Exercise Price Per Share, Outstanding \| $ / shares	23
Weighted Average Exercise Price Per Share, Vested and exercisable \| $ / shares	$ 23
Weighted Average Remaining Contract Term, Outstanding	6 years 8 months 12 days
Weighted Average Remaining Contract Term, Vested and exercisable	6 years 8 months 12 days
Weighted Aggregate Intrinsic Value, Outstanding \| $	$ 7,510
Weighted Aggregate Intrinsic Value, Vested and exercisable \| $	$ 7,510
Service Based Stock Option Activity [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Option, Outstanding \| shares	3,557,194
Number of Option, Granted \| shares	250,477
Number of Option, Exercised \| shares	(355,920)
Number of Option, Cancelled/Forfeited \| shares	(90,044)
Number of Option, Outstanding \| shares	3,361,707
Number of Option, Vested and exercisable \| shares	2,400,930
Weighted Average Exercise Price Per Share, Outstanding \| $ / shares	$ 25.57
Weighted Average Exercise Price Per Share, Granted \| $ / shares	20.18
Weighted Average Exercise Price Per Share, Exercised \| $ / shares	23
Weighted Average Exercise Price Per Share, Cancelled/Forfeited \| $ / shares	25.79
Weighted Average Exercise Price Per Share, Outstanding \| $ / shares	25.43
Weighted Average Exercise Price Per Share, Vested and exercisable \| $ / shares	$ 24.59
Weighted Average Remaining Contract Term, Outstanding	7 years 1 month 6 days
Weighted Average Remaining Contract Term, Vested and exercisable	6 years 9 months 18 days
Weighted Aggregate Intrinsic Value, Outstanding \| $	$ 19,871
Weighted Aggregate Intrinsic Value, Vested and exercisable \| $	$ 14,561

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock Awards Activity Other Than Options (Detail)	12 Months Ended
	Sep. 30, 2023 $ / shares shares
Service Based Restricted Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Outstanding and unvested \| shares	275,628
Number of Shares, Vested \| shares	(173,841)
Number of Shares, Forfeited \| shares	(19,306)
Number of Shares, Outstanding and unvested \| shares	82,481
Weighted Average Grant Date Fair Value, Outstanding and unvested	$ 23
Weighted Average Grant Date Fair Value, Granted	0
Weighted Average Grant Date Fair Value, Vested	23
Weighted Average Grant Date Fair Value, Forfeited	23
Weighted Average Grant Date Fair Value, Outstanding and unvested	$ 23
Performance Based Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Outstanding and unvested \| shares	221,469
Number of Shares, Granted \| shares	319,263
Number of Shares, Forfeited \| shares	(32,110)
Number of Shares, Outstanding and unvested \| shares	508,622
Weighted Average Grant Date Fair Value, Outstanding and unvested	$ 37.55
Weighted Average Grant Date Fair Value, Granted	20.18
Weighted Average Grant Date Fair Value, Forfeited	35.09
Weighted Average Grant Date Fair Value, Outstanding and unvested	$ 26.73

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Restricted Stock Unit Awards Activity (Detail) - Service Based Restricted Stock Units [Member]	12 Months Ended
	Sep. 30, 2023 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of Shares, Outstanding and unvested \| shares	574,499
Number of Shares, Granted \| shares	504,951
Number of Shares, Vested \| shares	(246,343)
Number of Shares, Forfeited \| shares	(47,011)
Number of Shares, Outstanding and unvested \| shares	786,096
Weighted Average Grant Date Fair Value, Outstanding and unvested \| $ / shares	$ 31.14
Weighted Average Grant Date Fair Value, Granted \| $ / shares	21.22
Weighted Average Grant Date Fair Value, Vested \| $ / shares	29.74
Weighted Average Grant Date Fair Value, Forfeited \| $ / shares	28.06
Weighted Average Grant Date Fair Value, Outstanding and unvested \| $ / shares	$ 25.39

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Defined Contribution Plan Disclosure [Line Items]
Percentage of employee salary contributed to plan	85%
Defined contribution plan, description	100% of the first 1% of employee contributions, plus 50% of the next 5% of employee contributions.
Company contribution to the plan	$ 4.9	$ 5.1	$ 4
First One Percent Employee [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of employee salary contributed to plan	100%
Next Five Percent Employee [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of employee salary contributed to plan	50%

Earnings Per Share - Summary of

Earnings Per Share - Summary of Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Numerator:
Net Income (Loss)	$ 67,955	$ 75,225	$ 93,150
Net income attributable to common stockholders - basic	67,955	75,225	93,150
Net income attributable to common stockholders - diluted	$ 67,955	$ 75,225	$ 93,150
Denominator:
Basic	150,162,256	153,510,110	153,777,859
Diluted	150,849,896	154,517,843	156,666,394
Basic	$ 0.45	$ 0.49	$ 0.61
Diluted	$ 0.45	$ 0.49	$ 0.59

Earnings Per Share - Summary _2

Earnings Per Share - Summary of Antidilutive Securities Excluded From Computation of Earnings Per Share (Detail) - shares	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,549,816	548,539	105,199
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	113,622	268,526	3,256

Income Taxes - Schedule of comp

Income Taxes - Schedule of components of the income tax expense (benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Federal	$ 25,216	$ 810	$ 200
State and local	8,200	8,260	2,939
Total current	33,416	9,070	3,139
Federal	(6,828)	19,302	26,240
State and local	(2,659)	382	(711)
Total deferred	(9,487)	19,684	25,529
Income tax expense	$ 23,929	$ 28,754	$ 28,668

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
Income Taxes - Additional Information (Detail) - USD ($)	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Effective income tax rate, Percent	21%	21%	21%
Effective income tax reconciliation percentage	26%	27.70%	23.50%
Deferred Tax Assets, Valuation Allowance	$ 5,557,000	$ 4,960,000	$ 5,310,000
Unrecognized Tax Benefits	900,000	780,000	$ 955,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	900,000	800,000
Deferred Income Tax Charge [Member]
Unrecognized Tax Benefits	900,000	800,000
Domestic Tax Authority [Member]
Operating Loss Carryforwards, subject to expiration	0
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, subject to expiration	$ 83,900,000
Operating Loss Carryforwards, Expiration Year	2043
Deferred Tax Assets, Valuation Allowance	$ 5,600,000	$ 5,000,000

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income tax expense / federal statutory rate	$ 19,296	$ 21,836	$ 25,583
State and local taxes - net of federal expense	3,218	7,257	2,329
Change in valuation allowance	597	(350)	(220)
Stock-based compensation	721	145	1,379
Non-deductible transaction costs			544
Executive compensation	608	364	704
Federal research and development credit	(746)	(703)	(1,829)
Meals and entertainment	284	224	267
Other	(49)	(19)	(89)
Income tax expense	$ 23,929	$ 28,754	$ 28,668
Income tax expense / federal statutory rate	21%	21%	21%
State and local taxes - net of federal expense	3.50%	7%	1.90%
Increase in valuation allowance	0.60%	(0.30%)	(0.20%)
Stock-based compensation	0.80%	0.10%	1.10%
Non-deductible transaction costs	0%	0%	0.40%
Executive compensation	0.70%	0.40%	0.60%
Federal research and development credit	(0.80%)	(0.70%)	(1.40%)
Meals and entertainment	0.30%	0.20%	0.20%
Other	(0.10%)	0%	(0.10%)
Income tax expense / effective tax rate	26%	27.70%	23.50%

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
State loss carryforwards and other benefits	$ 15,744	$ 13,699
Inventory reserves	14,203	13,852
Warranty reserves	4,148	3,839
Accrued expenses	11,996	10,607
Stock-based compensation	13,502	12,185
Lease liabilities	24,063	25,034
Valuation allowance	(5,557)	(4,960)	$ (5,310)
Total deferred tax assets	78,099	74,256
Intangible assets — net	37,272	42,197
Property, plant and equipment	74,611	73,471
Right-of-use assets	21,728	23,237
Unrealized gain in other comprehensive income	615
Indemnification receivable related to warranty reserves	203	546
Total deferred tax liabilities	134,429	139,451
Net deferred tax liability	$ 56,330	$ 65,195

Income Taxes - Summary of Valua

Income Taxes - Summary of Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Beginning balance	$ 4,960	$ 5,310
Expense	597	(350)
Ending balance	$ 5,557	$ 4,960

Income Taxes - Schedule of Unre

Income Taxes - Schedule of Unrecognized Tax Benefits Roll Forward (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Beginning balance	$ 780	$ 955
Unrecognized tax benefits related to prior years	70
Unrecognized tax benefits related to prior years		(230)
Unrecognized tax benefits related to the current year	50	55
Ending balance	$ 900	$ 780

Commitments And Contingencies -

Commitments And Contingencies - Additional Information (Detail) - USD ($)	Dec. 31, 2023	Sep. 30, 2023	Sep. 30, 2022
Loss Contingencies [Line Items]
Purchase Obligation		$ 400,000	$ 400,000
Scenario Forecast [Member]
Loss Contingencies [Line Items]
Purchase Obligation	$ 0

Condensed Financial Informati_3

Condensed Financial Information of Registrant (Parent Company Only) - Schedule of Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Non-current assets:
Total assets	$ 2,365,554	$ 2,383,091	$ 2,187,834
LIABILITIES AND STOCKHOLDERS’ EQUITY:
Total liabilities	935,911	938,648
Stockholders’ equity:
Preferred stock, $0.001 par value; 1,000,000 shares authorized and no shares issued and outstanding at September 30, 2023 and September 30, 2022, respectively
Additional paid-in capital	1,662,322	1,630,378
Accumulated deficit	(45,047)	(113,002)
Accumulated other comprehensive income (loss)	1,878
Treasury stock, at cost, 8,268,423 shares at September 30, 2023 and 4,116,570 shares at September 30, 2022	(189,666)	(73,088)
Total stockholders’ equity	1,429,643	1,444,443	$ 1,427,164	$ 1,303,888
Total liabilities and stockholders’ equity	2,365,554	2,383,091
Parent Company [Member]
Non-current assets:
Investments in subsidiaries	1,429,643	1,444,443
Total non-current assets	1,429,643	1,444,443
Total assets	1,429,643	1,444,443
Stockholders’ equity:
Additional paid-in capital	1,662,322	1,630,378
Accumulated deficit	(45,047)	(113,002)
Accumulated other comprehensive income (loss)	1,878
Treasury stock, at cost, 8,268,423 shares at September 30, 2023 and 4,116,570 shares at September 30, 2022	(189,666)	(73,088)
Total stockholders’ equity	1,429,643	1,444,443
Total liabilities and stockholders’ equity	1,429,643	1,444,443
Common Class A [Member]
Stockholders’ equity:
Common stock value	156	155
Common Class A [Member] \| Parent Company [Member]
Stockholders’ equity:
Common stock value	$ 156	$ 155

Condensed Financial Informati_4

Condensed Financial Information of Registrant (Parent Company Only) - Schedule of Balance Sheets (Parenthetical) (Detail) - $ / shares	Sep. 30, 2023	Sep. 30, 2022
Preferred stock, par value per share	$ 0.001	$ 0.001
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Treasury stock, shares	8,268,423	4,116,570
Common Class A [Member]
Common stock, par value per share	$ 0.001	$ 0.001
Common stock, shares authorized	1,100,000,000	1,100,000,000
Common stock, shares issued	155,967,736	155,157,220
Common stock, shares outstanding	147,699,313
Common Class B [Member]
Common stock, par value per share	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	100	100
Common stock, shares outstanding	100	100
Parent Company [Member]
Preferred stock, par value per share	$ 0.001	$ 0.001
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Treasury stock, shares	8,268,423	4,116,570
Parent Company [Member] \| Common Class A [Member]
Common stock, par value per share	$ 0.001	$ 0.001
Common stock, shares authorized	1,100,000,000	1,100,000,000
Common stock, shares issued	155,967,736	155,157,220
Parent Company [Member] \| Common Class B [Member]
Common stock, par value per share	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	100	100
Common stock, shares outstanding	100	100

Condensed Financial Informati_5

Condensed Financial Information of Registrant (Parent Company Only) - Schedule of Statements of Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Condensed Statement of Income Captions [Line Items]
Comprehensive income	$ 69,833	$ 75,225	$ 93,150
Parent Company [Member]
Condensed Statement of Income Captions [Line Items]
Net income of subsidiaries	67,955	75,225	93,150
Comprehensive income	$ 69,833	$ 75,225	$ 93,150

Condensed Financial Informati_6

Condensed Financial Information of Registrant (Parent Company Only) - Additional Information (Detail) - Parent Company [Member] - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Condensed Statement of Income Captions [Line Items]
Minimum threshold percentage of restricted net assets	25%
Cash dividends paid	$ 115.5	$ 73.1	$ 0
Accelerated share repurchased		50
Open Market [Member]
Condensed Statement of Income Captions [Line Items]
Share repurchase on open market	79.5	$ 23.1
Second Offering [Member]
Condensed Statement of Income Captions [Line Items]
Share repurchase on open market	$ 36

Subsequent Events - Additioanl

Subsequent Events - Additioanl Information (Detail)	Oct. 10, 2023
Subsequent Event [Member] \| Vycom Business [Member]
Subsequent Event [Line Items]
Sales transaction closing date	Nov. 01, 2023