SEGMENT INFORMATION (Details)	3 Months Ended
	Mar. 30, 2024 USD ($) segment	Apr. 01, 2023 USD ($)	Dec. 30, 2023 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	3
Number of reportable segments | segment	3
Total revenue	$ 805,015,000	$ 435,388,000
Loss from operations before taxes	(78,335,000)	(37,678,000)
Interest expense	51,892,000	27,420,000
Depreciation, depletion and amortization	94,963,000	50,188,000
Accretion	1,008,000	706,000
Loss on debt financings	5,453,000	493,000
Gain on sale of businesses	(14,985,000)	0
Non-cash compensation	6,720,000	4,708,000
Argos USA acquisition and integration costs	61,294,000	0
Other	(6,785,000)	(4,636,000)
Total Adjusted EBITDA	121,225,000	41,201,000
Total purchases of property, plant and equipment	58,519,000	63,584,000
Total depreciation, depletion, amortization and accretion	95,971,000	50,894,000
Total assets	8,129,900,000		$ 5,149,582,000
Operating segment
Segment Reporting Information [Line Items]
Total purchases of property, plant and equipment	54,104,000	60,688,000
Total depreciation, depletion, amortization and accretion	94,124,000	49,906,000
Total assets	7,612,107,000		3,913,666,000
Corporate and other
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(19,105,000)	(10,339,000)
Total purchases of property, plant and equipment	4,415,000	2,896,000
Total depreciation, depletion, amortization and accretion	1,847,000	988,000
Total assets	517,793,000		1,235,916,000
West
Segment Reporting Information [Line Items]
Total revenue	304,538,000	250,882,000
West | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	43,400,000	32,678,000
Total purchases of property, plant and equipment	25,844,000	38,174,000
Total depreciation, depletion, amortization and accretion	30,338,000	26,373,000
Total assets	1,970,633,000		1,837,214,000
East
Segment Reporting Information [Line Items]
Total revenue	268,694,000	130,389,000
Gain on sale of businesses	(15,000,000)
East | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	37,476,000	18,852,000
Total purchases of property, plant and equipment	16,224,000	15,518,000
Total depreciation, depletion, amortization and accretion	23,081,000	15,535,000
Total assets	1,608,962,000		1,171,944,000
Cement
Segment Reporting Information [Line Items]
Total revenue	231,783,000	54,117,000
Cement | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	59,454,000	10,000
Total purchases of property, plant and equipment	12,036,000	6,996,000
Total depreciation, depletion, amortization and accretion	40,705,000	7,998,000
Total assets	$ 4,032,512,000		904,508,000
Summit Materials, LLC
Segment Reporting Information [Line Items]
Number of operating segments | segment	3
Number of reportable segments | segment	3
Total revenue	$ 805,015,000	435,388,000
Loss from operations before taxes	(78,526,000)	(37,678,000)
Interest expense	51,892,000	27,420,000
Depreciation, depletion and amortization	94,963,000	50,188,000
Accretion	1,008,000	706,000
Loss on debt financings	5,453,000	493,000
Gain on sale of businesses	(14,985,000)	0
Non-cash compensation	6,720,000	4,708,000
Argos USA acquisition and integration costs	61,294,000	0
Other	(6,594,000)	(4,636,000)
Total Adjusted EBITDA	121,225,000	41,201,000
Total purchases of property, plant and equipment	58,519,000	63,584,000
Total depreciation, depletion, amortization and accretion	95,971,000	50,894,000
Total assets	8,245,278,000		5,212,529,000
Summit Materials, LLC | Operating segment
Segment Reporting Information [Line Items]
Total purchases of property, plant and equipment	54,104,000	60,688,000
Total depreciation, depletion, amortization and accretion	94,124,000	49,906,000
Total assets	7,612,107,000		3,913,666,000
Summit Materials, LLC | Corporate and other
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	(19,105,000)	(10,339,000)
Total purchases of property, plant and equipment	4,415,000	2,896,000
Total depreciation, depletion, amortization and accretion	1,847,000	988,000
Total assets	633,171,000		1,298,863,000
Summit Materials, LLC | West
Segment Reporting Information [Line Items]
Total revenue	304,538,000	250,882,000
Summit Materials, LLC | West | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	43,400,000	32,678,000
Total purchases of property, plant and equipment	25,844,000	38,174,000
Total depreciation, depletion, amortization and accretion	30,338,000	26,373,000
Total assets	1,970,633,000		1,837,214,000
Summit Materials, LLC | East
Segment Reporting Information [Line Items]
Total revenue	268,694,000	130,389,000
Gain on sale of businesses	(15,000,000)
Summit Materials, LLC | East | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	37,476,000	18,852,000
Total purchases of property, plant and equipment	16,224,000	15,518,000
Total depreciation, depletion, amortization and accretion	23,081,000	15,535,000
Total assets	1,608,962,000		1,171,944,000
Summit Materials, LLC | Cement
Segment Reporting Information [Line Items]
Total revenue	231,783,000	54,117,000
Summit Materials, LLC | Cement | Operating segment
Segment Reporting Information [Line Items]
Total Adjusted EBITDA	59,454,000	10,000
Total purchases of property, plant and equipment	12,036,000	6,996,000
Total depreciation, depletion, amortization and accretion	40,705,000	$ 7,998,000
Total assets	$ 4,032,512,000		$ 904,508,000