Employee Benefit Plan	12 Months Ended
Mar. 31, 2026
Retirement Benefits [Abstract]
Employee Benefit Plan	Employee Benefit Plan In the United States, the Company sponsors a defined contribution plan, the James Hardie Retirement and Profit Sharing Plan (the “401(k) Plan”) which is a tax-qualified retirement and savings plan covering all US employees, including the senior executive officers, subject to certain eligibility requirements. Under this plan, the Company matches employee contributions dollar for dollar, up to a maximum of the first 6% of an employee’s eligible compensation. In connection with the AZEK acquisition, the Company assumed the 401(k) defined contribution plans (the “401(k) Plans”) for the benefit of employees who meet certain eligibility requirements. The 401(k) Plans cover substantially all of the Company’s full-time employees. The 401(k) Plans match employee pre-tax and Roth IRA contributions. The Company matches 100% of the first 2% of employee contributions, plus 50% of the next 4% of employee contributions. For the fiscal years ended March 31, 2026, 2025 and 2024, the Company made total matching contributions of $25.2 million, $19.0 million and $16.8 million, respectively under the multiple 401(k) plans. The Company sponsors a deferred compensation plan for its executives whereby the plan assets are held in a rabbi trust. The deferred compensation is funded to the rabbi trust which holds investments directed by the participants and are accounted for as held for sale. The Company matches up to a maximum of the first 6% of an employee’s eligible compensation that would not be eligible in the 401(k) Plan due to Internal Revenue Service contribution limits so long as the participant defers eligible compensation to the deferred compensation plan. As of March 31, 2026, the assets held in trust and related deferred compensation liability recorded in the accompanying consolidated balance sheets are immaterial.

In the United States, the Company sponsors a defined contribution plan, the James Hardie Retirement and Profit Sharing Plan (the “401(k) Plan”) which is a tax-qualified retirement and savings plan covering all US employees, including the senior executive officers, subject to certain eligibility requirements. Under this plan, the Company matches employee contributions dollar for dollar, up to a maximum of the first 6% of an employee’s eligible compensation.

In connection with the AZEK acquisition, the Company assumed the 401(k) defined contribution plans (the “401(k) Plans”) for the benefit of employees who meet certain eligibility requirements. The 401(k) Plans cover substantially all of the Company’s full-time employees. The 401(k) Plans match employee pre-tax and Roth IRA contributions. The Company matches 100% of the first 2% of employee contributions, plus 50% of the next 4% of employee contributions.

For the fiscal years ended March 31, 2026, 2025 and 2024, the Company made total matching contributions of $25.2 million, $19.0 million and $16.8 million, respectively under the multiple 401(k) plans.

The Company sponsors a deferred compensation plan for its executives whereby the plan assets are held in a rabbi trust. The deferred compensation is funded to the rabbi trust which holds investments directed by the participants and are accounted for as held for sale. The Company matches up to a maximum of the first 6% of an employee’s eligible compensation that would not be eligible in the 401(k) Plan due to Internal Revenue Service contribution limits so long as the participant defers eligible compensation to the deferred compensation plan. As of March 31, 2026, the assets held in trust and related deferred compensation liability recorded in the accompanying consolidated balance sheets are immaterial.