INCOME TAXES (Details) - USD ($)	3 Months Ended			12 Months Ended
	Mar. 30, 2024	Sep. 30, 2023	Apr. 01, 2023	Dec. 31, 2015	Dec. 30, 2023
Income Taxes [Line Items]
Income tax benefit	$ (11,065,000)		$ (6,466,000)
Valuation allowance	1,113,000				$ 1,113,000
Income tax provision, interest or penalties recognized	$ 0		0
Tax Receivable Agreement
Income Taxes [Line Items]
Exchanges during period (in shares)	763,243
Increase in Tax Receivable Agreement liability	$ 6,700,000
Summit Holdings LP | Tax Receivable Agreement
Income Taxes [Line Items]
Percentage of benefits to be paid on tax receivable agreement	85.00%			85.00%
Summit Materials, LLC
Income Taxes [Line Items]
Income tax benefit	$ (196,000)		(467,000)
Income tax provision, interest or penalties recognized	0		$ 0
Current portion of tax receivable agreement interests	3,500,000				6,318,000
Tax receivable agreement interest, net of current portion	122,631,000				$ 126,131,000
Summit Materials, LLC | Tax Receivable Agreement
Income Taxes [Line Items]
Tax receivable agreement, rights and interests acquisition, consideration		$ 122,900,000
Current portion of tax receivable agreement interests	3,500,000
Tax receivable agreement interest, net of current portion	$ 122,600,000