STOCKHOLDERS' EQUITY/MEMBERS' INTEREST - Equity Offerings (Details) - shares	3 Months Ended
	Mar. 30, 2024	Apr. 01, 2023	Dec. 30, 2023	Dec. 31, 2022
Common Class A
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	119,529,380	118,408,655
Exchanges during period (in shares)	763,243	2,000
Stock option exercises (in shares)	29,216	902
Issuance of Class A common stock (in shares)	54,720,000
Other equity transactions (in shares)	412,411	407,114
Ending balance (in shares)	175,454,250	118,818,671
Summit Materials, Inc. and Summit Holdings, LP
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	120,292,623	119,720,659
Exchanges during period (in shares)	0	0
Stock option exercises (in shares)	29,216	902
Issuance of Class A common stock (in shares)	54,720,000
Other equity transactions (in shares)	412,411	407,114
Ending balance (in shares)	175,454,250	120,128,675
LP Units | Summit Holdings LP
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Number of LP Units outstanding, beginning balance (in shares)	763,243	1,312,004
Number of LP Units exchanged (in shares)	(763,243)	(2,000)
Number of LP Units outstanding, ending balance (in shares)	0	1,310,004
Summit Materials Inc
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ownership percentage	100.00%	98.90%	99.40%	98.90%