Property, Plant and Equipment, net and Intangibles, net - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 33,864	$ 26,707
Accumulated Amortization	(10,366)	(8,247)
Net Carrying Amount	23,498	18,460
Amortization expense	2,100	1,500	$ 1,300
Estimated amortization expense
2020	2,526
2021	2,138
2022	2,142
2023	2,009
2024	1,914
Thereafter	12,769
Total	23,498	18,460
Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	33,864	26,707
Accumulated Amortization	(10,366)	(8,247)
Net Carrying Amount	23,498	18,460
Amortization expense	2,100	1,500	$ 1,300
Estimated amortization expense
2020	2,526
2021	2,138
2022	2,142
2023	2,009
2024	1,914
Thereafter	12,769
Total	23,498	18,460
Mineral leases
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	19,064	19,064
Accumulated Amortization	(6,408)	(5,259)
Net Carrying Amount	12,656	13,805
Mineral leases | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	19,064	19,064
Accumulated Amortization	(6,408)	(5,259)
Net Carrying Amount	12,656	13,805
Reserve rights
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,234	6,234
Accumulated Amortization	(2,248)	(1,940)
Net Carrying Amount	3,986	4,294
Reserve rights | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,234	6,234
Accumulated Amortization	(2,248)	(1,940)
Net Carrying Amount	3,986	4,294
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,000	1,000
Accumulated Amortization	(958)	(858)
Net Carrying Amount	42	142
Trade names | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,000	1,000
Accumulated Amortization	(958)	(858)
Net Carrying Amount	42	142
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,566	409
Accumulated Amortization	(752)	(190)
Net Carrying Amount	6,814	219
Other | Summit Materials, LLC
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,566	409
Accumulated Amortization	(752)	(190)
Net Carrying Amount	$ 6,814	$ 219