EX-10.4



 Exhibit 10.4 

AMENDMENT NO. 1 TO EXCHANGE AGREEMENT 

This AMENDMENT NO. 1 TO EXCHANGE AGREEMENT, dated as of August [    ], 2015 (this “Amendment”) is entered
into by and among Summit Materials, Inc., a Delaware corporation (the “Corporation”), Summit Materials Holdings L.P., a Delaware limited partnership (“Summit Holdings”), and each of the other parties identified on
the signature pages hereto (the “Financial Sponsor Holders”). This Amendment is an amendment to the Exchange Agreement, dated as of March 11, 2015 (the “Agreement”). Capitalized terms used herein but not
defined herein shall have the meanings assigned to such terms in the Agreement. 
 RECITALS: 

WHEREAS, the Exchange Agreement provides that it may be amended by the affirmative vote or written consent of each of (i) the
Corporation, (ii) Summit Holdings, (iii) LP Unitholders holding a majority of the then outstanding LP Units (excluding LP Units held by the Corporation) and (iv) for so long as the Financial Sponsor Holders collectively own, in the
aggregate, at least 5% of the outstanding LP Units, each of the Financial Sponsor Holders; and 
 WHEREAS, the Financial Sponsor Holders
hold more than a majority of the outstanding LP Units (excluding LP Units held by the Corporation) as of the date hereof. 
 NOW THEREFORE,
in consideration of the premises and agreements hereinafter set forth, the parties hereto hereby each consent in writing to and agree as follows: 

Section 1. Amendment. The Agreement is hereby amended to insert the following as a new clause (h) to Section 2.1 of the
Agreement: 
 “(h) Purchases by the Corporation and/or its subsidiaries of LP Units (including, without limitation, in
connection with a “synthetic secondary” offering) shall for purposes of this Agreement constitute transfers to the Corporation in accordance with this Agreement.” 

Section 2. Status. This Amendment amends the Agreement, but only to the extent expressly set forth herein. All other provisions of
the Agreement remain in full force and effect. 
 Section 3. Governing Law. This Amendment shall be governed by, and construed
in accordance with, the laws of the State of Delaware. 
 Section 4. Counterparts. This Amendment may be executed in one
or more counterparts, each of which shall be deemed to be an original, but all of which shall be considered one and the same instrument. 

Section 5. Facsimile Execution. Facsimile signatures on counterparts of this Amendment are hereby authorized and shall be
acknowledged as if such facsimile signatures were an original execution, and this Amendment shall be deemed as executed when an executed facsimile hereof is transmitted by a party to any other party. 

[Remainder of Page Intentionally Left Blank] 







 IN WITNESS WHEREOF, the parties have caused this Amendment to be duly executed and delivered, all
as of the date first set forth above. 
  

			
	Corporation:
	
	SUMMIT MATERIALS, INC.
		
	By:	 	  

	Name:	 	Thomas W. Hill
	Title:	 	Chief Executive Officer
	
	Summit Holdings:
	
	SUMMIT MATERIALS HOLDINGS L.P.
	
	By: SUMMIT MATERIALS, INC., its general partner
		
	By:	 	  

	Name:	 	Thomas W. Hill
	Title:	 	Chief Executive Officer









 
			
	Financial Sponsor Holders:
	
	BLACKSTONE PARTICIPATION PARTNERSHIP (DELAWARE) V-NQ L.P.
	
	By: BCP V-NQ GP L.L.C., its U.S. general partner
		
	By:	 	  

	Name:	 	Neil P. Simpkins
	Title:	 	Senior Managing Director
	
	BLACKSTONE FAMILY INVESTMENT PARTNERSHIP (DELAWARE) V-NQ L.P.
	
	By: BCP V-NQ GP L.L.C., its U.S. general partner
		
	By:	 	  

	Name:	 	Neil P. Simpkins
	Title:	 	Senior Managing Director
	
	BLACKSTONE CAPITAL PARTNERS (DELAWARE) V-NQ L.P.
	
	By: Blackstone Management Associates (Cayman) V-NQ L.P., its general partner
	
	By: BCP V-NQ GP L.L.C., its U.S. general partner
		
	By:	 	  

	Name:	 	Neil P. Simpkins
	Title:	 	Senior Managing Director









 
			
	BLACKSTONE CAPITAL PARTNERS (DELAWARE) NQ V-AC L.P.
	
	By: Blackstone Management Associates (Cayman) V-NQ L.P., its general partner
	
	By: BCP V-NQ GP L.L.C., its U.S. general partner
		
	By:	 	  

	Name:	 	Neil P. Simpkins
	Title:	 	Senior Managing Director
	
	SUMMIT BCP INTERMEDIATE HOLDINGS L.P.
	
	By: Summit BCP Intermediate Holdings GP, Ltd., its general partner
		
	By:	 	  

	Name:	 	Neil P. Simpkins
	Title:	 	Director