INVENTORIES - Components of Inventories (Details) - USD ($) $ in Thousands	Sep. 28, 2019	Dec. 29, 2018
Inventory [Line Items]
Aggregate stockpiles	$ 142,618	$ 151,300
Finished goods	25,240	34,993
Work in process	7,478	7,478
Raw materials	21,679	20,080
Total	197,015	213,851
Summit Materials, LLC
Inventory [Line Items]
Aggregate stockpiles	142,618	151,300
Finished goods	25,240	34,993
Work in process	7,478	7,478
Raw materials	21,679	20,080
Total	$ 197,015	$ 213,851

Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of merchandise or goods held by the company that are readily available for sale.

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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Amount before last-in first-out (LIFO) and valuation reserves of ore stockpile material contained on a leach pad, for example, but not limited to, copper or gold ore.

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of unprocessed items to be consumed in the manufacturing or production process.

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Carrying amount, net of reserves and adjustments, as of the balance sheet date of merchandise or goods which are partially completed. This inventory is generally comprised of raw materials, labor and factory overhead costs, which require further materials, labor and overhead to be converted into finished goods, and which generally require the use of estimates to determine percentage complete and pricing.

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