Exhibit 10.1

AMENDMENT NO. 1 TO EXCHANGE AGREEMENT

This AMENDMENT NO. 1 TO EXCHANGE AGREEMENT, dated as of August 4, 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.

[Amendment No. 1 to Exchange Agreement]

--------------------------------------------------------------------------------

[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:  

/s/ Thomas W. Hill

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

/s/ Thomas W. Hill

Name:   Thomas W. Hill Title:   Chief Executive Officer

 

[Amendment No. 1 to Exchange Agreement]

--------------------------------------------------------------------------------

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:  

/s/ Neil P. Simpkins

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:  

/s/ Neil P. Simpkins

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:  

/s/ Neil P. Simpkins

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:  

/s/ Neil P. Simpkins

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:  

/s/ Neil P. Simpkins

Name:   Neil P. Simpkins Title:   Director