Document:

EX-10.8

 Exhibit 10.8 

NONQUALIFIED STOCK OPTION AGREEMENT 

(Leverage Restoration Options) 

Summit Materials, Inc. 

2015 Omnibus Incentive Plan 

This Nonqualified Stock Option Agreement (this “Agreement”), effective as of the Date of Grant (as defined below), is between
Summit Materials, Inc., a Delaware corporation (the “Company”), and the Participant (as defined below). 
 WHEREAS,
the Company has adopted the Summit Materials, Inc. 2015 Omnibus Incentive Plan (the “Plan”) in order to provide additional incentives to selected officers and employees of the Company and its Subsidiaries; 

WHEREAS, pursuant to an IPO Reorganization Agreement, a reorganization of the various classes of interests of the Partnership (the
“Reclassification”), was or will be effected on or about the pricing of the initial public offering (the “IPO”) of the Class A common stock, par value, $0.01 per share (the “Common Stock”) of
the Company; and 
 WHEREAS, in connection with the Reclassification, the Committee (as defined in the Plan) responsible for
administration of the Plan has determined to grant an option to the Participant as provided herein and the Company and the Participant hereby wish to memorialize the terms and conditions applicable to the Option (as defined below). 

NOW, THEREFORE, the parties hereto agree as follows: 

1. Definitions. Capitalized terms not otherwise defined herein shall have the same meanings as in the Plan. The following terms shall
have the following meanings for purposes of this Agreement: 
 (a) “Agreement” shall mean this Nonqualified Stock Option
Agreement including (unless the context otherwise requires) the Award Notice and the appendix for non-U.S. Participants attached hereto as Appendix B. 

(b) “Award Notice” shall mean the notice to the Participant attached hereto as Exhibit A. 

(c) “Exercise Price” shall mean the “Exercise Price” listed in the Award Notice. 

(d) “Date of Grant” shall mean the “Date of Grant” listed in the Award Notice. 

(e) “Participant” shall mean the “Participant” listed in the Award Notice. 

(f) “Restrictive Covenant Violation” shall mean the Participant’s breach of the Restrictive Covenants listed on Appendix
A or any covenant regarding confidentiality, competitive activity, solicitation of the Company’s vendors, suppliers, customers, or employees, or any similar provision applicable to or agreed to by the Participant. 

 (g) “Shares” shall mean the number of shares of Common Stock listed in the Award
Notice as “Number of Shares Subject to Option”. 
 2. Grant of Options. 

(a) Effective as of the Date of Grant, for good and valuable consideration, the Company hereby irrevocably grants to the Participant the right
and option (the “Option”) to purchase all or any part of the Shares, subject to, and in accordance with, the terms, conditions and restrictions set forth in the Plan and this Agreement. 

(b) The Option is not intended to qualify as an Incentive Stock Option within the meaning of Section 422 of the Code. 

(c) This Agreement shall be construed in accordance and consistent with, and subject to, the terms of the Plan (the provisions of which are
incorporated hereby by reference); and, except as otherwise expressly set forth herein, the capitalized terms used in this Agreement shall have the same definitions as set forth in the Plan. In the event of any conflict between one or more of this
Agreement, the Award Notice and the Plan, the Plan shall govern this Agreement and the Award Notice, and the Agreement (to the extent not in conflict with the Plan) shall govern the Award Notice. 

3. Exercise Price. The price at which the Participant shall be entitled to purchase the Shares upon the exercise of the Option shall be
the Exercise Price per share, subject to adjustment as provided in Section 9. 
 4. Exercisability of Option. The Option shall
become vested and exercisable in accordance with the schedule set forth on the Award Notice. 
 5. Duration of Option. The Option
shall be exercisable to the extent and in the manner provided herein for a period of 10 years from the Date of Grant (the “Option Period”); provided, however, that the Option may be earlier terminated as provided in
Section 7 hereof. 
 6. Manner of Exercise and Payment. 

(a) Subject to the terms and conditions of this Agreement and the Plan, the Option may be exercised by delivery of written or electronic
notice to the Company in the manner prescribed in Section 7(d) of the Plan and as otherwise set forth by the Committee from time to time. Such notice shall set forth the number of Shares in respect of which the Option is being exercised and
shall be signed by the person or persons exercising the Option. In the event the Company has designated an Award Administrator (as defined below), the Option may also be exercised by giving notice (including through electronic means) in accordance
with the procedures established from time to time by the Award Administrator. Any exercisable portion of the Option or the entire Option, if then wholly exercisable, may be exercised in whole or in part, provided that partial exercise shall be for
whole shares of Common Stock only. 
 (b) Upon exercise of the Option pursuant to Section 6(a), unless otherwise determined by the
Committee, the Company shall withhold a number of Shares otherwise 

  
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deliverable to the Participant to pay (i) the full purchase price for the Shares in respect of which the Option is being exercised (the “Aggregate Exercise Price”) and
(ii) the minimum applicable withholding taxes, liabilities, and obligations (“Withholding Taxes”) associated with such exercise. 

(c) Upon receipt of the notice of exercise and any payment or other documentation as may be necessary pursuant to Sections 6(a) and 6(b)
relating to the Shares in respect of which the Option is being exercised, the Company shall, subject to the Plan and this Agreement, take such action as may be necessary to effect the transfer to the Participant of the number of Shares as to which
such exercise was effective (less any Shares withheld pursuant to Section 6(b)). 
 (d) The Participant shall not be deemed to be the
holder of, or to have any of the rights and privileges of a stockholder of the Company (including the right to vote or receive dividends) in respect of, Shares purchased upon exercise of the Option until (i) the Option shall have been exercised
pursuant to the terms of this Agreement and the Participant shall have paid the Aggregate Exercise Price associated with such exercise and any applicable Withholding Taxes and (ii) the Company shall have issued the Shares in connection with
such exercise. 
 7. Termination of Employment. 

(a) Subject to Section 7(c) below, in the event that the Participant’s employment with the Company and its Subsidiaries is
terminated for any reason, any unvested portion of the Option shall be forfeited and all of the Participant’s rights hereunder with respect to such unvested portion of the Option shall terminate as of the effective date of termination (the
“Termination Date”) (unless otherwise provided for by the Committee in accordance with the Plan, and except for any Option that is eligible to vest after the Termination Date pursuant to the Award Notice, which Option, if any, shall
remain outstanding until the later of (x) the date such Option is no longer able to become vested in accordance with the terms of the Award Notice, or (y) 90 days following the date such Option becomes vested). 

(b) Notwithstanding any portion of this Agreement to the contrary, if the Participant’s employment is terminated by the Company or any
Subsidiary with Cause or by the Participant when grounds existed for Cause at the time thereof, the vested and unvested portions of the Option shall terminate as of the Termination Date. 

(c) In the event of (i) the Participant’s employment with the Company and its Subsidiaries is terminated by the Company due to death
or Disability, each outstanding vested Option shall remain exercisable for one year thereafter (but in no event beyond the Option Period) and (ii) the Participant’s employment with the Company and its Subsidiaries is terminated for any
other reason (subject to Section 7(b)), each outstanding vested Option shall remain exercisable for 90 days thereafter (but in no event beyond the Option Period); provided that, in each case, the Option Period shall expire immediately upon the
occurrence of a Restrictive Covenant Violation. 
 (d) The Participant’s rights with respect to the Option shall not be affected by any
change in the nature of the Participant’s employment so long as the Participant continues to be an 

  
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employee of the Company or any of its Subsidiaries. Whether (and the circumstances under which) employment has been terminated and the determination of the Termination Date for the purposes of
this Agreement shall be determined by the Committee (or, with respect to any Participant who is not a director or “officer” as defined under Rule 16a-1(f) under the Securities Exchange Act of 1934, as amended, its designee, whose good
faith determination shall be final, binding and conclusive; provided, that such designee may not make any such determination with respect to the designee’s own employment for purposes of the Option). 

8. Restrictions on Transfer. The Participant may not assign, alienate, pledge, attach, sell or otherwise transfer or encumber the
Option or the Participant’s right under the Option to receive Shares, except other than by will or by the laws of descent and distribution and any such purported assignment, alienation, pledge, attachment, sale, transfer or encumbrance shall be
void and unenforceable against the Company or an Affiliate; provided that the designation of a beneficiary (if permitted by the Committee) shall not constitute an assignment, alienation, pledge, attachment, sale, transfer or encumbrance. 

9. Restrictive Covenants. Participant acknowledges and recognizes the highly competitive nature of the businesses of the Company and
its Affiliates and accordingly agrees to the provisions of Appendix A to this Agreement (the “Restrictive Covenants”). For the avoidance of doubt, the Restrictive Covenants contained in this Agreement are in addition to, and not in
lieu of, any other restrictive covenants or similar covenants or agreements between the Participant and the Company or any of its Affiliates. 

10. Repayment of Proceeds; Clawback Policy. If a Restrictive Covenant Violation occurs or the Company discovers after a termination of
employment that grounds existed for Cause at the time thereof, then Participant shall be required, in addition to any other remedy available (on a non-exclusive basis), to pay to the Company, within 10 business days of the Company’s request to
Participant therefor, an amount equal to the excess, if any, of (a) the aggregate after-tax proceeds (taking into account all amounts of tax that would be recoverable upon a claim of loss for payment of such proceeds in the year of repayment)
Participant received upon the sale or other disposition of, or distributions in respect of, the Options and any Shares acquired in respect thereof over (b) the aggregate Cost (if any) of such Shares. For purposes of this Agreement,
“Cost” means, in respect of any Share, the amount paid by Participant for the Share (excluding, for the avoidance of doubt, any Withholding Taxes), as proportionately adjusted for corporate transactions and other recapitalizations
and less the amount of any dividends or distributions made with respect to the Share; provided that Cost may not be less than zero. Any reference in this Agreement to grounds existing for a termination of employment with Cause shall be determined
without regard to any notice period, cure period, or other procedural delay or event required prior to finding of or termination with, Cause. The Option and all proceeds of the Option shall be subject to the Company’s Clawback Policy, as in
effect from time to time, to the extent Participant is a director or “officer” as defined under Rule 16a-1(f) of the Securities Exchange Act of 1934, as amended. 

11. No Right to Continued Employment. Neither the Plan nor this Agreement nor the Participant’s receipt of the Option hereunder
shall impose any obligation on the Company or any Affiliate to continue the employment or engagement of the Participant. Further, the Company or any Affiliate (as applicable) may at any time terminate the employment or engagement of such
Participant, free from any liability or claim under the Plan or this Agreement, except as otherwise expressly provided herein. 

  
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 12. Adjustments. The terms of this Agreement, including, without limitation, (a) the
number of Shares subject to the Option and (b) the Exercise Price specified herein, shall be subject to adjustment in accordance with Section 12 of the Plan. 

13. Award Subject to Plan. By entering into this Agreement, the Participant agrees and acknowledges that the Participant has received
and read a copy of the Plan. The Option granted hereunder is subject to the Plan. The terms and provisions of the Plan, as it may be amended from time to time, are hereby incorporated herein by reference. In the event of a conflict between any term
or provision contained herein and a term or provision of the Plan, the applicable terms and provisions of the Agreement will govern and prevail. 

14. Severability. Should any provision of this Agreement be held by a court of competent jurisdiction to be unenforceable or invalid
for any reason, the remaining provisions of this Agreement shall not be affected by such holding and shall continue in full force in accordance with their terms. 

15. Governing Law; Venue; Language. This Agreement shall be governed by and construed in accordance with the laws of the State of
Delaware. Any suit, action or proceeding with respect to this Agreement, or any judgment entered by any court in respect of any thereof, shall be brought in any court of competent jurisdiction specified in the Fourth Amended and Restated Limited
Partnership Agreement of the Partnership (as amended from time to time, the “LP Agreement”). The Participant and the Company each hereby irrevocably waives (a) any objections which it may now or hereafter have to the laying of
the venue of any suit, action or proceeding arising out of or relating to this Agreement brought in any court of competent jurisdiction in any jurisdiction specified in the LP Agreement, (b) any claim that any such suit, action or proceeding
brought in any such court has been brought in any inconvenient forum and (c) any right to a jury trial. 
 16. Successors in
Interest. Any successor to the Company shall have the benefits of the Company under, and be entitled to enforce, this Agreement. Likewise, the Participant’s legal representative shall have the benefits of Participant under, and be entitled
to enforce, this Agreement. All obligations imposed upon the Participant and all rights granted to the Company under this Agreement shall be final, binding and conclusive upon the Participant’s heirs, executors, administrators and successors.

 17. Data Privacy Consent. The Participant hereby explicitly and unambiguously consents to the collection, use and transfer, in
electronic or other form, of the Participant’s personal data as described in this Agreement and any other Option grant materials by and among, as applicable, the Participant’s employer or contracting party (the “Employer”)
and the Company for the exclusive purpose of implementing, administering and managing the Participant’s participation in the Plan. The Participant understands that the Company may hold certain personal information about the Participant,
including, but not limited to, the Participant’s name, home address and telephone number, work location and phone number, date of birth, social insurance number or other identification number, salary, nationality, job title, hire date,

  
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any shares of stock or directorships held in the Company, details of all awards or any other entitlement to shares awarded, cancelled, exercised, vested, unvested or outstanding in the
Participant’s favor, for the purpose of implementing, administering and managing the Plan (“Personal Data”). The Participant understands that Personal Data may be transferred to any third parties assisting in the
implementation, administration and management of the Plan, now or in the future, that these recipients may be located in the Participant’s country or elsewhere, and that the recipient’s country may have different data privacy laws and
protections than the Participant’s country. The Participant understands that the Participant may request a list with the names and addresses of any potential recipients of the Personal Data by contacting the Participant’s local human
resources representative. The Participant authorizes the recipients to receive, possess, use, retain and transfer the Personal Data, in electronic or other form, for the purposes of implementing, administering and managing the Participant’s
participation in the Plan. The Participant understands that Personal Data will be held only as long as is necessary to implement, administer and manage the Participant’s participation in the Plan. The Participant understands that the
Participant may, at any time, view Personal Data, request additional information about the storage and processing of Personal Data, require any necessary amendments to Personal Data or refuse or withdraw the consents herein, in any case without
cost, by contacting in writing the Participant’s local human resources representative. Further, the Participant understands that the Participant is providing the consents herein on a purely voluntary basis. If the Participant does not consent,
or if the Participant later seeks to revoke the Participant’s consent, the Participant’s employment status or service and career with the Employer will not be adversely affected; the only consequence of the Participant’s refusing or
withdrawing the Participant’s consent is that the Company would not be able to grant Options or other equity awards to the Participant or administer or maintain such awards. Therefore, the Participant understands that refusing or withdrawing
the Participant’s consent may affect the Participant’s ability to participate in the Plan. For more information on the consequences of Participant’s refusal to consent or withdrawal of consent, the Participant understands that the
Participant may contact the Participant’s local human resources representative. 
 18. Limitation on Rights; No Right to Future
Grants; Extraordinary Item of Compensation. By accepting this Agreement and the grant of the Option evidenced hereby, the Participant expressly acknowledges that: (a) the Plan is discretionary in nature and may be suspended or terminated by
the Company at any time; (b) the grant of the Option is a one-time benefit that does not create any contractual or other right to receive future grants of options, or benefits in lieu of options; (c) all determinations with respect to
future option grants, if any, including the grant date, the number of Shares granted, the exercise price and the exercise date or dates, will be at the sole discretion of the Company; (d) the Participant’s participation in the Plan is
voluntary; (e) the value of the Option is an extraordinary item of compensation that is outside the scope of the Participant’s employment contract, if any, and nothing can or must automatically be inferred from such employment contract or
its consequences; (f) Options are not part of normal or expected compensation for any purpose and are not to be used for calculating any severance, resignation, redundancy, end of service payments, bonuses, long-service awards, pension or
retirement benefits or similar payments, the Participant waives any claim on such basis and, for the avoidance of doubt, the Option shall not constitute an “acquired right” under the applicable law of any jurisdiction; (g) if the
underlying Shares do not increase in value, the Option will have no value; (h) if the Participant exercises the Option and acquires Shares, the 

  
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value of such Shares may increase or decrease in value, even below the exercise price; and (i) the future value of the underlying Shares is unknown and cannot be predicted with certainty. In
addition, the Participant understands, acknowledges and agrees that the Participant will have no rights to compensation or damages related to option proceeds in consequence of the termination of the Participant’s employment for any reason
whatsoever and whether or not in breach of contract. 
 19. Award Administrator. The Company may from time to time designate a third
party (an “Award Administrator”) to assist the Company in the implementation, administration and management of the Plan and any Options granted thereunder, including by sending Award Notices on behalf of the Company to Participants,
and by facilitating through electronic means acceptance of Agreement by Participants and Option exercises by Participants. 
 20. Book
Entry Delivery of Shares. Whenever reference in this Agreement is made to the issuance or delivery of certificates representing one or more Shares, the Company may elect to issue or deliver such Shares in book entry form in lieu of certificates.

 21. Electronic Delivery and Acceptance. The Company may, in its sole discretion, decide to deliver any documents related to
current or future participation in the Plan by electronic means. The Participant hereby consents to receive such documents by electronic delivery and agrees to participate in the Plan through an on-line or electronic system established and
maintained by the Company or a third party designated by the Company. 
 22. Acceptance and Agreement by the Participant; Forfeiture upon
Failure to Accept. By accepting this Option (including through electronic means), the Participant agrees to be bound by the terms, conditions, and restrictions set forth in the Plan, this Agreement, and the Company’s policies, as in effect
from time to time, relating to the Plan. The Participant’s rights under the Option will lapse 90 days from the Date of Grant, and the Option will be forfeited on such date if the Participant shall not have accepted this Agreement by such date.
For the avoidance of doubt, the Participant’s failure to accept this Agreement shall not affect the Participant’s continuing obligations under any other agreement between the Company and the Participant. 

23. No Advice Regarding Grant. The Company is not providing any tax, legal or financial advice, nor is the Company making any
recommendations regarding the Participant’s participation in the Plan, or the Participant’s acquisition or sale of the underlying Shares. The Participant is hereby advised to consult with his or her own personal tax, legal and financial
advisors regarding his or her participation in the Plan before taking any action related to the Plan. 
 24. Appendices For Non-U.S.
Participants. Notwithstanding any provisions in this Agreement, Participants residing and/or working outside the United States shall be subject to the Terms and Conditions for Non-U.S. Participants attached hereto as Appendix B. If the
Participant relocates from the United States to another country, the Terms and Conditions for Non-U.S. Participants and the applicable Country-Specific Terms and Conditions will apply to the Participant, to the extent the Company determines that the
application of such terms and conditions is necessary or advisable for legal or administrative reasons. Moreover, if the 

  
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Participant relocates between any of the countries included in Country-Specific Terms and Conditions, the special terms and conditions for such country will apply to the Participant, to the
extent the Company determines that the application of such terms and conditions is necessary or advisable for legal or administrative reasons. The Terms and Conditions for Non-U.S. Participants and the Country-Specific Terms and Conditions
constitute part of this Agreement. 
 25. Imposition of Other Requirements. The Company reserves the right to impose other
requirements on the Participant’s participation in the Plan, on the Option and on any Shares acquired under the Plan, to the extent the Company determines it is necessary or advisable for legal or administrative reasons, and to require the
Participant to sign any additional agreements or undertakings that may be necessary to accomplish the foregoing. 
 26. Waiver. The
Participant acknowledges that a waiver by the Company of breach of any provision of this Agreement shall not operate or be construed as a waiver of any other provision of this Agreement, or of any subsequent breach by the Participant or any other
participant in the Plan. 
 [Signatures follow] 

  
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	SUMMIT MATERIALS, INC.
		
	By:	 	  

		 	 Name: Thomas W. Hill
 Title: Chief Executive
Officer

 Acknowledged and Agreed 

as of the date first written above: 
  

	
	
	  

	Participant Signature

 Exhibit A - 1 

Exhibit A 

Summit Materials, Inc. 

Nonqualified Stock Option Award Notice 

Participant: 
 Date of Grant: 

Vesting Start Date: 
 Exercise Price: 

 Number of Shares Subject to Option: 

Time-Vesting Options: 
 1.75x MOIC
Performance-Vesting Options: 
 3.00x MOIC Performance-Vesting Options: 

Vesting Schedule: 
 1. Time-Based
Vesting Options. 
 (a) So long as the Participant’s employment with the Company and its Affiliates has not been terminated (the
“Termination Date”), 25% of the Time-Vesting Options shall become vested on each of the first four anniversaries of the Vesting Start Date. 

(b) Notwithstanding the foregoing, immediately prior to, and following, the occurrence of a Change in Control that occurs prior to the
Participant’s Termination Date, 100% of the Time-Vesting Options shall become vested and exercisable. 
 2. Performance-Based
Vesting Options. 
 (a) Vesting Conditions. The 1.75x MOIC Performance-Vesting Options and 3.00x MOIC Performance-Vesting Options
(collectively, “Performance-Vesting Options”) shall be subject to, and only be considered vested and exercisable upon satisfaction of, both a Service Vesting Condition and a Performance Vesting Condition, and a Performance-Based
Vesting Option shall only become vested and exercisable beginning on the first date that the Service Vesting Condition and the Performance Vesting Condition are both satisfied with respect to such Performance-Based Vesting Option. 

(b) 1.75x MOIC-Vesting Terms. 

(i) The Service Vesting Condition shall be satisfied with respect to 25% of the 1.75x MOIC Performance-Vesting Options on each
of the first four anniversaries of the Vesting Start Date, subject to the Participant’s continued employment through each such vesting date. 

 Exhibit A - 2 
  

 (ii) The Performance Vesting Condition applicable to all 1.75x MOIC
Performance-Vesting Options shall be satisfied at such time prior to June 30, 2020 that the Sponsor shall have received aggregate cash proceeds and/or has distributed to its limited partners marketable securities (in each case, not subject to
any clawback, indemnity or similar contractual obligation) in respect of its Units (as defined in the LP Agreement) in the Partnership equal to, or in the case of marketable securities having a fair market value equal to, at least 175% of its
aggregate Capital Contributions (as defined in the LP Agreement) in respect of such Units (the “1.75x Hurdle”), then all of the 1.75x MOIC Performance-Vesting Options shall become vested and exercisable. 

(c) 3.00x MOIC-Vesting Terms. 

(i) The Service Vesting Condition shall be satisfied with respect to 25% of the 3.00x MOIC Performance-Vesting Options on each
of the first four anniversaries of the Vesting Start Date, subject to the Participant’s continued employment through each such vesting date. 

(ii) The Performance Vesting Condition applicable to all 3.00x MOIC Performance-Vesting Options shall be satisfied at such time
prior to June 30, 2020 that the Sponsor shall have received aggregate cash proceeds and/or has distributed to its limited partners marketable securities (in each case, not subject to any clawback, indemnity or similar contractual obligation) in
respect of its Units in the Partnership equal to, or in the case of marketable securities having a fair market value equal to, at least 300% of its aggregate Capital Contributions in respect of such Units (the “3.00x Hurdle”), then
all of the 3.00x MOIC Performance-Vesting Options shall become vested and exercisable. 
 3. Forfeiture Upon Termination of
Employment. 
 (a) Any Time-Vesting Options that are unvested on a Termination Date shall be immediately forfeited by the Participant.

 (b) Subject to Section 3(c) of this Award Notice, any Performance-Vesting Options that are unvested on a Termination Date shall be
immediately forfeited by the Participant 
 (c) Notwithstanding Section 3(b) of this Award Notice 

(i) In the event a transaction closes before the earlier of the Termination Date or June 30, 2020 and a portion of the
proceeds are subject to any clawback, indemnity or similar obligation, then any Performance-Vesting Options with respect to which the applicable Service Vesting Condition was satisfied prior to the Termination Date shall remain eligible for
additional vesting following such date until the effect of any clawback, indemnity or similar contractual obligation is finally determined (and shall vest or not vest at the time of such final determination if the relevant hurdle is met); 

 Exhibit A - 3 
  

 (ii) If the Participant’s employment is terminated without Cause or if
the Participant has entered into a written employment agreement with the Company that includes a definition of “good reason” or “constructive termination,” if the Participant resigns for “good reason” or
“constructive termination” (as defined in such written employment agreement) (any such termination, a “Qualifying Termination”), any Performance-Vesting Options with respect to which the applicable Service Vesting
Condition was satisfied prior to the Termination Date shall remain outstanding and eligible to vest for 12 months following such Termination Date, provided that such Performance-Vesting Options shall only be eligible to vest in accordance with
Section 2 of this Award Notice if a Change in Control occurs during such 12-month period, and 
 (iii) If the
Participant experiences a Qualifying Termination in the 12 months following a Change in Control, then the Sponsor shall be deemed to have received cash proceeds in an amount equal to the value of their equity interests in the Company and its
Affiliates immediately prior to the applicable Termination Date (as determined in good faith by the Board, but valuing shares of Common Stock using a 30-day volume-weighted average price preceding the Termination Date), for purposes of this Award
Notice and determining achievement of the 1.75x MOIC Hurdle and 3.00x MOIC Hurdle. 

 Appendix A 

Restrictive Covenants 

Confidentiality; Non-Compete; Non-Solicit; Non-Disparagement. 

(a) For the purposes of this Appendix A, any reference to the “Company” shall mean the Company and its Subsidiaries and Affiliates,
collectively. In view of the fact that Participant’s work for the Company brings Participant into close contact with many confidential affairs of the Company not readily available to the public, and plans for further developments, Participant
agrees: 
 (i) Participant will not at any time (whether during or after Participant’s Employment with the Company):
(x) retain or use for the benefit, purposes or account of Participant or any other person; or (y) disclose, divulge, reveal, communicate, share, transfer or provide access to any person outside the Company (other than its professional
advisers who are bound by confidentiality obligations), any non-public, proprietary or confidential information – including without limitation trade secrets, know-how, research and development, software, databases, inventions, processes,
formulae, technology, designs and other intellectual property, information concerning finances, investments, profits, pricing, costs, products, services, vendors, customers, clients, partners, investors, personnel, compensation, recruiting,
training, advertising, sales, marketing, promotions, government and regulatory activities and approvals – concerning the past, current or future business, activities and operations of the Company, its Subsidiaries or Affiliates and/or any third
party that has disclosed or provided any of same to the Company on a confidential basis (“Confidential Information”) without the prior written authorization of the Board, except as specifically necessary during the term of
Participant’s Employment in order to perform the duties of his or her position and in the best interests of the Company. 

(ii) “Confidential Information” shall not include any information that is: (a) generally known to the industry
or the public other than as a result of Participant’s breach of this covenant or any breach of other confidentiality obligations by third parties; (b) made legitimately available to Participant by a third party without breach of any
confidentiality obligation; or (c) required by law to be disclosed; provided that Participant shall give prompt written notice to the Company of such requirement, disclose no more information than is so required, and cooperate with any
attempts by the Company to obtain a protective order or similar treatment. 
 (iii) Except as required by law, Participant
will not disclose to anyone, other than Participant’s immediate family and legal or financial advisors, the existence or contents of this Agreement; provided that Participant may disclose to any prospective future employer the provisions
of Section (b) of this Appendix provided they agree to maintain the confidentiality of such terms. 
 (iv) Upon
termination of Participant’s Employment with the Company for any reason, Participant shall (x) cease and not thereafter commence use of any Confidential Information or intellectual property (including without limitation, any

 Appendix A - 2 
  

 
patent, invention, copyright, trade secret, trademark, trade name, logo, domain name or other source indicator) owned or used by the Company, its Subsidiaries or Affiliates; (y) immediately
destroy, delete, or return to the Company, at the Company’s option, all originals and copies in any form or medium (including memoranda, books, papers, plans, computer files, letters and other data) in Participant’s possession or control
(including any of the foregoing stored or located in Participant’s office, home, laptop or other computer, whether or not Company property) that contain Confidential Information or otherwise relate to the business of the Company, its Affiliates
and Subsidiaries, except that Participant may retain only those portions of any personal notes, notebooks and diaries that do not contain any Confidential Information; and (z) notify and fully cooperate with the Company regarding the delivery
or destruction of any other Confidential Information of which Participant is or becomes aware. 
 (b) Participant acknowledges and
recognizes the highly competitive nature of the businesses of the Company and its Affiliates and accordingly agrees as follows: 

(i) Participant will not, within twelve months following the termination of Participant’s Employment with the Company or
such shorter time as provided in Section 1(b)(iv) (the “Post-Termination Period”) or during Participant’s Employment (collectively with the Post-Termination Period, the “Restricted Period”): 

(A) engage in any business involved, either directly or indirectly, in (x) the acquisition of companies primarily engaged
in the U.S. and Canadian aggregates and related downstream product sectors (including, but not limited to, asphalt, paving, cement, concrete and concrete products) (any such company, a “Business”) or (y) the operation of any
Business (any such business as described in subclauses (x) or (y), a “Competitive Business”). 
 (B)
enter the employ of, or render any services to, any person (or any division or controlled or controlling affiliate of any person) who or which engages in a Competitive Business; 

(C) acquire a financial interest in, or otherwise become actively involved with, any Competitive Business, directly or
indirectly, as an individual, partner, shareholder, officer, director, principal, agent, trustee or consultant; or 
 (D)
interfere with, or attempt to interfere with, business relationships (whether formed before, on or after the date of this Agreement) between the Company or any of its Affiliates and customers, clients, suppliers, partners, members, investors or
acquisition targets. 
 (ii) During the Restricted Period, Participant will not, whether on Participant’s own behalf or
on behalf of or in conjunction with any person, directly or indirectly: 
 (A) solicit or encourage any employee of the
Company or its Affiliates to leave the Employment of the Company or its Affiliates; or 

 Appendix A - 3 
  

 (B) hire any such employee who was employed by the Company or its Affiliates
as of the date of Participant’s termination of Employment with the Company or who left the Employment of the Company or its Affiliates coincident with, or within one year prior to or after, the termination of Participant’s Employment with
the Company. 
 (iii) During the Restricted Period, Participant will not, whether on Participant’s own behalf or on
behalf of or in conjunction with any person, directly or indirectly solicit or assist in soliciting in competition with the Company, the business of any client or prospective client: 

(A) with whom Participant had personal contact or dealings on behalf of the Company during the one-year period preceding
Participant’s termination of Employment; 
 (B) with whom employees reporting to Participant have had personal contact
or dealings on behalf of the Company during the one year immediately preceding Participant’s termination of Employment; or 

(C) for whom Participant had direct or indirect responsibility during the one year immediately preceding Participant’s
termination of Employment. 
 Notwithstanding anything to the contrary in this Agreement, Participant may, directly or indirectly own,
solely as an investment, securities of any person which are publicly traded on a national or regional stock exchange or on the over-the-counter market if Participant (i) is not a controlling person of, or a member of a group which controls,
such person and (ii) does not, directly or indirectly, own 5% or more of any class of securities of such person. 
 (c) During the
Restricted Period, Participant will not, directly or indirectly, solicit or encourage to cease to work with the Company or its Affiliates any consultant then under contract with the Company or its Affiliates. 

(d) Participant will not, other than as required by law or by order of a court or other competent authority, make or publish, or cause any
other person to make or publish, any statement that is disparaging or that reflects negatively upon the Company or its Affiliates, or that is or reasonably would be expected to be damaging to the reputation of the Company or its Affiliates. 

(e) It is expressly understood and agreed that although Participant and the Company consider the restrictions contained in this Appendix A to
be reasonable, if a final judicial determination is made by a court of competent jurisdiction, that the time or territory or any other restriction contained in this Agreement is an unenforceable restriction against Participant, the provisions of
this Agreement shall not be rendered void but shall be deemed amended to apply as to such maximum time and territory and to such maximum extent as such court may judicially determine or indicate to be enforceable. Alternatively, if any court of
competent jurisdiction finds that any restriction contained in this Agreement is unenforceable, and such restriction cannot be amended so as to make it enforceable, such finding shall not affect the enforceability of any of the other restrictions
contained herein. 

 Appendix A - 4 
  

 (f) The period of time during which the provisions of this Appendix A shall be in effect
shall be extended by the length of time during which Participant is in breach of the terms hereof as determined by any court of competent jurisdiction on the Company’s application for injunctive relief. 

2. Specific Performance; Survival. 

(a) Participant acknowledges and agrees that the Company’s remedies at law for a breach or threatened breach of any of the provisions of
this Appendix A would be inadequate and the Company would suffer irreparable damages as a result of such breach or threatened breach. In recognition of this fact, Participant agrees that, in the event of such a breach or threatened breach, in
addition to any remedies at law, the Company, without posting any bond, shall be entitled to suspend making any payments or providing any benefit otherwise required by this Agreement and obtain equitable relief in the form of specific performance,
temporary restraining order, temporary or permanent injunction or any other equitable remedy which may then be available. 
 (b) The provisions of this
Appendix A shall survive the termination of Participant’s Employment for any reason. 

 Appendix B - 1 

APPENDIX B 

SUMMIT MATERIALS, INC. 

2015 OMNIBUS INCENTIVE PLAN 

NONQUALIFIED STOCK OPTION AGREEMENT 

TERMS AND CONDITIONS FOR NON-U.S. PARTICIPANTS 

Capitalized terms used but not otherwise defined herein shall have the meaning given to such terms in the Plan and the Nonqualified Stock
Option Agreement. 
 1. Responsibility for Taxes. This provision supplements Section 6 of the Nonqualified Stock Option
Agreement: 
 (a) The Participant acknowledges that, regardless of any action taken by the Company or, if different, the Employer the
ultimate liability for all income tax, social insurance, payroll tax, fringe benefits tax, payment on account or other tax-related items related to the Participant’s participation in the Plan and legally applicable to the Participant
(“Tax-Related Items”) is and remains the Participant’s responsibility and may exceed the amount actually withheld by the Company or the Employer. The Participant further acknowledges that the Company and/or the Employer
(1) make no representations or undertakings regarding the treatment of any Tax-Related Items in connection with any aspect of the Option, including, but not limited to, the grant, vesting or exercise of the Option, the subsequent sale of Shares
acquired pursuant to such exercise and the receipt of any dividends and/or any other distributions; and (2) do not commit to and are under no obligation to structure the terms of the grant or any aspect of the Option to reduce or eliminate the
Participant’s liability for Tax-Related Items or achieve any particular tax result. Further, if the Participant is subject to Tax-Related Items in more than one jurisdiction between the Date of Grant and the date of any relevant taxable or tax
withholding event, as applicable, the Participant acknowledges that the Company and/or the Employer (or former employer, as applicable) may be required to withhold or account for Tax-Related Items in more than one jurisdiction. 

(b) Prior to any relevant taxable or tax withholding event, as applicable, the Participant agrees to make adequate arrangements satisfactory
to the Company and/or the Employer to satisfy all Tax-Related Items. In this regard, the Participant authorizes the Company and/or the Employer, or their respective agents, at their discretion, to satisfy their withholding obligations with regard to
all Tax-Related Items by: 
 (i) withholding from the Participant’s wages or other cash compensation paid to the
Participant by the Company and/or the Employer; or 
 (ii) withholding from proceeds of the sale of Shares acquired at
exercise of the Option either through a voluntary sale or through a mandatory sale arranged by the Company (on the Participant’s behalf pursuant to this authorization) without further consent; or 

 Appendix B - 2 
  

 (iii) withholding in Shares to be issued upon exercise of the Option; 

provided, however, that if the Participant is a Section 16 officer of the Company under the Exchange Act, then the Company will withhold in Shares upon
the relevant taxable or tax withholding event, as applicable, unless the use of such withholding method is problematic under applicable tax or securities law or has materially adverse accounting consequences, in which case, the obligation for
Tax-Related Items may be satisfied by one or a combination of methods (i) and (ii) above. 
 (c) Depending on the withholding
method, the Company may withhold or account for Tax-Related Items by considering applicable minimum statutory withholding rates or other applicable withholding rates, including maximum applicable rates, in which case the Participant will receive a
refund of any over-withheld amount in cash and will have no entitlement to the Common Stock equivalent. If the obligation for Tax-Related Items is satisfied by withholding in Shares, for tax purposes, the Participant is deemed to have been issued
the full number of Shares subject to the portion of the Option that is exercised, notwithstanding that a number of the Shares are held back solely for the purpose of paying the Tax-Related Items 

(d) Finally, the Participant agrees to pay to the Company or the Employer, any amount of Tax-Related Items that the Company or the Employer
may be required to withhold or account for as a result of the Participant’s participation in the Plan that cannot be satisfied by the means previously described. The Company may refuse to issue or deliver the Shares or the proceeds of the sale
of Shares if the Participant fails to comply with the Participant’s obligations in connection with the Tax-Related Items. 
 2.
Nature of Grant. This provision supplements Section 18 of the Nonqualified Stock Option Agreement: 
 In accepting the grant of the
Option, the Participant acknowledges, understands and agrees that: 
 (a) the Option grant and the Participant’s participation in the
Plan shall not create a right to employment or be interpreted as forming an employment or services contract with the Company or any Affiliate; 

(b) the Option and the Shares subject to the Option are not intended to replace any pension rights or compensation; 

(c) for purposes of the Option, the Termination Date shall be the date the Participant is no longer actively providing services to the Company
or its Affiliates (regardless of the reason for such termination and whether or not later to be found invalid or in breach of employment laws in the jurisdiction where the Participant is employed or the terms of the Participant’s employment
agreement, if any), and unless otherwise expressly provided in this Agreement or determined by the Company, the Participant’s right to vest in the Option under the Plan, if any, will terminate and the Participant’s right to exercise any
vested Option, if any, will be measured as of such date and will not be extended by any notice period (e.g., the Participant’s period of service would not include any contractual notice period or any period of “garden leave”

 Appendix B - 3 
  

 
or similar period mandated under employment laws in the jurisdiction where the Participant is employed or the terms of the Participant’s employment agreement, if any); the Committee shall
have the exclusive discretion to determine when the Participant is no longer actively providing services for purposes of the Option grant (including whether the Participant may still be considered to be providing services while on a leave of
absence); 
 (d) unless otherwise provided in the Plan or by the Company in its discretion, the Option and the benefits evidenced by this
Agreement do not create any entitlement to have the Option or any such benefits transferred to, or assumed by, another company nor to be exchanged, cashed out or substituted for, in connection with any corporate transaction affecting the
Company’s Common Stock; and 
 (e) neither the Company nor any Affiliate shall be liable for any foreign exchange rate fluctuation
between the Participant’s local currency and the United States Dollar that may affect the value of the Option or of any amounts due to the Participant pursuant to the exercise of the Option or the subsequent sale of any Shares acquired upon
exercise. 
 3. Insider Trading Restrictions/Market Abuse Laws. The Participant acknowledges that, depending on his or her country of
residence, the Participant may be subject to insider trading restrictions and/or market abuse laws, which may affect his or her ability to acquire or sell Shares or rights to Shares (e.g., Options) under the Plan during such times as the
Participant is considered to have “inside information” regarding the Company (as defined by the laws in the Participant’s country). Any restrictions under these laws or regulations are separate from and in addition to any restrictions
that may be imposed under any applicable Company insider trading policy. The Participant is responsible for ensuring compliance with any applicable restrictions and is advised to consult his or her personal legal advisor on this matter.EX-10.9

 Exhibit 10.9 

INDEMNIFICATION AGREEMENT 

This Indemnification Agreement is effective as of
[                    ], (this “Agreement”) and is between Summit Materials, Inc., a Delaware corporation (the
“Company”), and the undersigned director/officer of the Company (the “Indemnitee”). 

Background 
 The
Company believes that, in order to attract and retain highly competent persons to serve as directors or in other capacities, including as officers, it must provide such persons with adequate protection through indemnification against the risks of
claims and actions against them arising out of their services to and activities on behalf of the Company. 
 The Company desires and has
requested Indemnitee to serve as a director and/or officer of the Company and, in order to induce the Indemnitee to serve in such capacity, the Company is willing to grant the Indemnitee the indemnification provided for herein. Indemnitee is willing
to so serve on the basis that such indemnification be provided. 
 The parties by this Agreement desire to set forth their agreement
regarding indemnification and the advancement of expenses. 
 In consideration of Indemnitee’s service to the Company and the covenants
and agreements set forth below, and for other good and valuable consideration, the receipt and adequacy of which are hereby acknowledged, the parties hereto, intending to be legally bound, hereby agree as follows. 

Section 1. Indemnification. 

To the fullest extent permitted by the General Corporation Law of the State of Delaware (the “DGCL”):

 (a) The Company shall indemnify Indemnitee if Indemnitee was or is made or is threatened to be made a party to, or is otherwise
involved in, as a witness or otherwise, any threatened, pending or completed action, suit or proceeding (brought in the right of the Company or otherwise), whether civil, criminal, administrative or investigative and whether formal or informal,
including appeals, by reason of the fact that Indemnitee is or was or has agreed to serve as a director, officer, employee or agent of the Company, or while serving as a director or officer of the Company, is or was serving or has agreed to serve at
the request of the Company as a director, officer, employee or agent (which, for purposes hereof, shall include a trustee, fiduciary, partner or manager or similar capacity) of another corporation, limited liability company, partnership, joint
venture, trust, employee benefit plan or other enterprise, or by reason of any action alleged to have been taken or omitted in any such capacity. 

(b) The indemnification provided by this Section 1 shall be from and against all loss and liability suffered and expenses
(including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by or on behalf of Indemnitee in connection with such action, suit or proceeding, including any appeals. 

Section 2. Advance Payment of Expenses. To the fullest extent permitted by the DGCL, expenses (including
attorneys’ fees) incurred by Indemnitee in appearing at, participating in or defending any action, suit or proceeding or in connection with an enforcement action as 

 
contemplated by Section 3(e), shall be paid by the Company in advance of the final disposition of such action, suit or proceeding within 30 days after receipt by the Company of a
statement or statements from Indemnitee requesting such advance or advances from time to time. The Indemnitee hereby undertakes to repay any amounts advanced (without interest) to the extent that it is ultimately determined that Indemnitee is not
entitled under this Agreement to be indemnified by the Company in respect thereof. No other form of undertaking shall be required of Indemnitee other than the execution of this Agreement. This Section 2 shall be subject to
Section 3(b) and shall not apply to any claim made by Indemnitee for which indemnity is excluded pursuant to Section 6. 

Section 3. Procedure for Indemnification; Notification and Defense of Claim. 

(a) Promptly after receipt by Indemnitee of notice of the commencement of any action, suit or proceeding, Indemnitee shall, if a claim in
respect thereof is to be made against the Company hereunder, notify the Company in writing of the commencement thereof. The failure to promptly notify the Company of the commencement of the action, suit or proceeding, or of Indemnitee’s request
for indemnification, will not relieve the Company from any liability that it may have to Indemnitee hereunder, except to the extent the Company is actually and materially prejudiced in its defense of such action, suit or proceeding as a result of
such failure. To obtain indemnification under this Agreement, Indemnitee shall submit to the Company a written request therefor including such documentation and information as is reasonably available to Indemnitee and is reasonably necessary to
enable the Company to determine whether and to what extent Indemnitee is entitled to indemnification. 
 (b) With respect to any action,
suit or proceeding of which the Company is so notified as provided in this Agreement, the Company shall, subject to the last two sentences of this paragraph, be entitled to assume the defense of such action, suit or proceeding, with counsel
reasonably acceptable to Indemnitee, upon the delivery to Indemnitee of written notice of its election to do so. After delivery of such notice, approval of such counsel by Indemnitee and the retention of such counsel by the Company, the Company will
not be liable to Indemnitee under this Agreement for any subsequently-incurred fees of separate counsel engaged by Indemnitee with respect to the same action, suit or proceeding unless the employment of separate counsel by Indemnitee has been
previously authorized in writing by the Company. Notwithstanding the foregoing, if Indemnitee, based on the advice of his or her counsel, shall have reasonably concluded (with written notice being given to the Company setting forth the basis for
such conclusion) that, in the conduct of any such defense, there is or is reasonably likely to be a conflict of interest or position between the Company and Indemnitee with respect to a significant issue, then the Company will not be entitled,
without the written consent of Indemnitee, to assume such defense. In addition, the Company will not be entitled, without the written consent of Indemnitee, to assume the defense of any claim brought by or in the right of the Company. 

(c) To the fullest extent permitted by the DGCL, the Company’s assumption of the defense of an action, suit or proceeding in accordance
with paragraph (b) above will constitute an irrevocable acknowledgement by the Company that any loss and liability suffered by Indemnitee and expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement by
or for the account of Indemnitee incurred in connection therewith are indemnifiable by the Company under Section 1 of this Agreement. 

(d) The determination whether to grant Indemnitee’s indemnification request shall be made promptly and in any event within 30 days
following the Company’s receipt of a request for indemnification in accordance with Section 3(a). If the Company determines that 

  
 2 

 
Indemnitee is entitled to such indemnification or, as contemplated by paragraph (c) above, the Company has acknowledged such entitlement, the Company will make payment to Indemnitee
of the indemnifiable amount within such 30 day period. If the Company is not deemed to have so acknowledged such entitlement or the Company’s determination of whether to grant Indemnitee’s indemnification request shall not have been made
within such 30 day period, the requisite determination of entitlement to indemnification shall, subject to Section 6, nonetheless be deemed to have been made and Indemnitee shall be entitled to such indemnification, absent (i) a
misstatement by Indemnitee of a material fact, or an omission of a material fact necessary to make Indemnitee’s statement not materially misleading, in connection with the request for indemnification, or (ii) a prohibition of such
indemnification under the DGCL. 
 (e) In the event that (i) the Company determines in accordance with this Section 3 that
Indemnitee is not entitled to indemnification under this Agreement, (ii) the Company denies a request for indemnification, in whole or in part, or fails to respond or make a determination of entitlement to indemnification within 30 days
following receipt of a request for indemnification as described above, (iii) payment of indemnification is not made within such 30 day period, (iv) advancement of expenses is not timely made in accordance with Section 2, or
(v) the Company or any other person takes or threatens to take any action to declare this Agreement void or unenforceable, or institutes any litigation or other action or proceeding designed to deny, or to recover from, the Indemnitee the
benefits provided or intended to be provided to Indemnitee hereunder, Indemnitee shall be entitled to an adjudication in any court of competent jurisdiction of his or her entitlement to such indemnification or advancement of expenses.
Indemnitee’s expenses (including attorneys’ fees) incurred in connection with successfully establishing Indemnitee’s right to indemnification or advancement of expenses, in whole or in part, in any such proceeding or otherwise shall
also be indemnified by the Company to the fullest extent permitted by the DGCL. 
 (f) Indemnitee shall be presumed to be entitled to
indemnification and advancement of expenses under this Agreement upon submission of a request therefor in accordance with Section 2 or Section 3 of this Agreement, as the case may be. The Company shall have the burden of
proof in overcoming such presumption, and such presumption shall be used as a basis for a determination of entitlement to indemnification and advancement of expenses unless the Company overcomes such presumption by clear and convincing evidence.

 Section 4. Insurance and Subrogation. 

(a) The Company shall use its reasonable best efforts to purchase and maintain a policy or policies of insurance with reputable insurance
companies with A.M. Best ratings of “A” or better, providing Indemnitee with coverage for any liability asserted against, and incurred by, Indemnitee or on Indemnitee’s behalf by reason of the fact that Indemnitee is or was or has
agreed to serve as a director, officer, employee or agent of the Company, or while serving as a director or officer of the Company, is or was serving or has agreed to serve at the request of the Company as a director, officer, employee or agent
(which, for purposes hereof, shall include a trustee, fiduciary, partner or manager or similar capacity) of another corporation, limited liability company, partnership, joint venture, trust, employee benefit plan or other enterprise, or arising out
of Indemnitee’s status as such, whether or not the Company would have the power to indemnify Indemnitee against such liability under the provisions of this Agreement. Such insurance policies shall have coverage terms and policy limits at least
as favorable to Indemnitee as the insurance coverage provided to any other director or officer of the Company. If the Company has such insurance in effect at the time the Company receives from Indemnitee any notice of the commencement of an action,
suit or proceeding, the Company shall give prompt 

  
 3 

 
notice of the commencement of such action, suit or proceeding to the insurers in accordance with the procedures set forth in the policy. The Company shall thereafter take all necessary or
desirable action to cause such insurers to pay, on behalf of Indemnitee, all amounts payable as a result of such proceeding in accordance with the terms of such policy. 

(b) Subject to Section 9(b), in the event of any payment by the Company under this Agreement, the Company shall be subrogated to
the extent of such payment to all of the rights of recovery of Indemnitee with respect to any insurance policy. Indemnitee shall execute all papers required and take all action necessary to secure such rights, including execution of such documents
as are necessary to enable the Company to bring suit to enforce such rights in accordance with the terms of such insurance policy. The Company shall pay or reimburse all expenses actually and reasonably incurred by Indemnitee in connection with such
subrogation. 
 (c) Subject to Section 9(b), the Company shall not be liable under this Agreement to make any payment of amounts
otherwise indemnifiable hereunder (including, but not limited to, judgments, fines and amounts paid in settlement, and excise taxes or penalties relating to the Employee Retirement Income Security Act of 1974, as amended) if and to the extent that
Indemnitee has otherwise actually received such payment under this Agreement or any insurance policy, contract, agreement or otherwise. 

Section 5. Certain Definitions. For purposes of this Agreement, the following definitions shall apply: 

(a) The term “action, suit or proceeding” shall be broadly construed and shall include, without limitation, the
investigation, preparation, prosecution, defense, settlement, arbitration and appeal of, and the giving of testimony in, any threatened, pending or completed claim, action, suit, arbitration, alternative dispute mechanism or proceeding, whether
civil, criminal, administrative or investigative. 
 (b) The term “by reason of the fact that Indemnitee is or was or has agreed
to serve as a director, officer, employee or agent of the Company, or while serving as a director or officer of the Company, is or was serving or has agreed to serve at the request of the Company as a director, officer, employee or agent (which, for
purposes hereof, shall include a trustee, partner or manager or similar capacity) of another corporation, limited liability company, partnership, joint venture, trust, employee benefit plan or other enterprise” shall be broadly
construed and shall include, without limitation, any actual or alleged act or omission to act. 
 (c) The term
“expenses” shall be broadly construed and shall include, without limitation, all direct and indirect costs of any type or nature whatsoever (including, without limitation, all attorneys’ fees and related disbursements,
appeal bonds, other out-of-pocket costs and reasonable compensation for time spent by Indemnitee for which Indemnitee is not otherwise compensated by the Company or any third party), actually and reasonably incurred by Indemnitee in connection with
either the investigation, defense or appeal of an action, suit or proceeding or establishing or enforcing a right to indemnification under this Agreement or otherwise incurred in connection with a claim that is indemnifiable hereunder. 

(d) The term “judgments, fines and amounts paid in settlement” shall be broadly construed and shall include, without
limitation, all direct and indirect payments of any type or nature whatsoever, as well as any penalties or excise taxes assessed on a person with respect to an employee benefit plan). 

  
 4 

 Section 6. Limitation on Indemnification. 

Notwithstanding any other provision herein to the contrary, the Company shall not be obligated pursuant to this Agreement: 

(a) Claims Initiated by Indemnitee. To indemnify or advance expenses to Indemnitee with respect to an action, suit or proceeding (or
part thereof), however denominated, initiated by Indemnitee, other than (i) an action, suit or proceeding brought to establish or enforce a right to indemnification or advancement of expenses under this Agreement (which shall be governed by the
provisions of Section 6(b) of this Agreement) and (ii) an action, suit or proceeding (or part thereof) that was authorized or consented to by the board of directors of the Company, it being understood and agreed that such
authorization or consent shall not be unreasonably withheld in connection with any compulsory counterclaim brought by Indemnitee in response to an action, suit or proceeding otherwise indemnifiable under this agreement. 

(b) Action for Indemnification. To indemnify Indemnitee for any expenses incurred by Indemnitee with respect to any action, suit or
proceeding instituted by Indemnitee to enforce or interpret this Agreement, unless Indemnitee is successful in such action, suit or proceeding in establishing Indemnitee’s right, in whole or in part, to indemnification or advancement of
expenses hereunder (in which case such indemnification or advancement shall be to the fullest extent permitted by the DGCL), or unless and to the extent that the court in such action, suit or proceeding shall determine that, despite
Indemnitee’s failure to establish his or her right to indemnification, Indemnitee is entitled to indemnification for such expenses; provided, however, that nothing in this Section 6(b) is intended to limit the
Company’s obligations with respect to the advancement of expenses to Indemnitee in connection with any such action, suit or proceeding instituted by Indemnitee to enforce or interpret this Agreement, as provided in Section 2 hereof.

 (c) Section 16(b) Matters. To indemnify Indemnitee on account of any suit in which judgment is rendered against Indemnitee
for disgorgement of profits made from the purchase or sale by Indemnitee of securities of the Company pursuant to the provisions of Section 16(b) of the Securities Exchange Act of 1934, as amended. 

(d) Fraud or Willful Misconduct. To indemnify Indemnitee on account of conduct by Indemnitee where such conduct has been determined by
a final (not interlocutory) judgment or other adjudication of a court or arbitration or administrative body of competent jurisdiction as to which there is no further right or option of appeal or the time within which an appeal must be filed has
expired without such filing to have been knowingly fraudulent or constitute willful misconduct. 
 (e) Prohibited by Law. To
indemnify Indemnitee in any circumstance where such indemnification has been determined by a final (not interlocutory) judgment or other adjudication of a court or arbitration or administrative body of competent jurisdiction as to which there is no
further right or option of appeal or the time within which an appeal must be filed has expired without such filing to be prohibited by law. 

Section 7. Certain Settlement Provisions. The Company shall have no obligation to indemnify Indemnitee
under this Agreement for any amounts paid in settlement of any action, 

  
 5 

 
suit or proceeding without the Company’s prior written consent. The Company shall not settle any action, suit or proceeding in any manner that would impose any fine or other obligation on
Indemnitee without Indemnitee’s prior written consent. Neither the Company nor Indemnitee will unreasonably withhold his, her, its or their consent to any proposed settlement. 

Section 8. Savings Clause. If any provision or provisions (or portion thereof) of this Agreement shall be
invalidated on any ground by any court of competent jurisdiction, then the Company shall nevertheless indemnify Indemnitee if Indemnitee was or is made or is threatened to be made a party or is otherwise involved in any threatened, pending or
completed action, suit or proceeding (brought in the right of the Company or otherwise), whether civil, criminal, administrative or investigative and whether formal or informal, including appeals, by reason of the fact that Indemnitee is or was or
has agreed to serve as a director, officer, employee or agent of the Company, or while serving as a director or officer of the Company, is or was serving or has agreed to serve at the request of the Company as a director, officer, employee or agent
(which, for purposes hereof, shall include a trustee, partner or manager or similar capacity) of another corporation, limited liability company, partnership, joint venture, trust, employee benefit plan or other enterprise, or by reason of any action
alleged to have been taken or omitted in such capacity, from and against all loss and liability suffered and expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement reasonably incurred by or on behalf of Indemnitee
in connection with such action, suit or proceeding, including any appeals, to the fullest extent permitted by any applicable portion of this Agreement that shall not have been invalidated. 

Section 9. Contribution/Jointly Indemnifiable Claims. 

(a) In order to provide for just and equitable contribution in circumstances in which the indemnification provided for herein is held by a
court of competent jurisdiction to be unavailable to Indemnitee in whole or in part, it is agreed that, in such event, the Company shall, to the fullest extent permitted by the DGCL, contribute to the payment of all of Indemnitee’s loss and
liability suffered and expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement reasonably incurred by or on behalf of Indemnitee in connection with any action, suit or proceeding, including any appeals, in an
amount that is just and equitable in the circumstances; provided, that, without limiting the generality of the foregoing, such contribution shall not be required where such holding by the court is due to any limitation on indemnification set
forth in Section 4(c), 6 (other than clause (e)) or 7 hereof. 
 (b) Given that certain jointly
indemnifiable claims may arise due to the service of the Indemnitee as a director and/or officer of the Company at the request of the Indemnitee-related entities, the Company acknowledges and agrees that the Company shall be fully and primarily
responsible for the payment to the Indemnitee in respect of indemnification or advancement of expenses in connection with any such jointly indemnifiable claim, pursuant to and in accordance with the terms of this Agreement, irrespective of any right
of recovery the Indemnitee may have from the Indemnitee-related entities. Under no circumstance shall the Company be entitled to any right of subrogation against or contribution by the Indemnitee-related entities and no right of advancement,
indemnification or recovery the Indemnitee may have from the Indemnitee-related entities shall reduce or otherwise alter the rights of the Indemnitee or the obligations of the Company hereunder. In the event that any of the Indemnitee-related
entities shall make any payment to the Indemnitee in respect of indemnification or advancement of expenses with respect to any jointly indemnifiable claim, the Indemnitee-related entity making such payment shall be subrogated to the extent of such
payment to all of the rights of recovery of the Indemnitee against the Company, and Indemnitee shall execute all papers reasonably required 

  
 6 

 
and shall do all things that may be reasonably necessary to secure such rights, including the execution of such documents as may be necessary to enable the Indemnitee-related entities effectively
to bring suit to enforce such rights. The Company and Indemnitee agree that each of the Indemnitee-related entities shall be third-party beneficiaries with respect to this Section 9(b), entitled to enforce this Section 9(b)
as though each such Indemnitee-related entity were a party to this Agreement. For purposes of this Section 9(b), the following terms shall have the following meanings: 

(i) The term “Indemnitee-related entities” means any corporation, limited liability company, partnership, joint venture, trust,
employee benefit plan or other enterprise (other than the Company or any other corporation, limited liability company, partnership, joint venture, trust, employee benefit plan or other enterprise Indemnitee has agreed, on behalf of the Company or at
the Company’s request, to serve as a director, officer, employee or agent and which service is covered by the indemnity described in this Agreement) from whom an Indemnitee may be entitled to indemnification or advancement of expenses with
respect to which, in whole or in part, the Company may also have an indemnification or advancement obligation (other than as a result of obligations under an insurance policy). 

(ii) The term “jointly indemnifiable claims” shall be broadly construed and shall include, without limitation, any action, suit or
proceeding for which the Indemnitee shall be entitled to indemnification or advancement of expenses from both the Indemnitee-related entities and the Company pursuant to the DGCL, any agreement or the certificate of incorporation, bylaws,
partnership agreement, operating agreement, certificate of formation, certificate of limited partnership or comparable organizational documents of the Company or the Indemnitee-related entities, as applicable. 

Section 10. Form and Delivery of Communications. All notices, requests, demands and other communications under this
Agreement shall be in writing and shall be deemed to have been duly given if (a) delivered by hand, upon receipt by the party to whom said notice or other communication shall have been directed, (b) mailed by certified or registered mail
with postage prepaid, on the third business day after the date on which it is so mailed, (c) mailed by reputable overnight courier, one day after deposit with such courier and with written verification of receipt or (d) sent by email or
facsimile transmission, with receipt of oral or written confirmation that such transmission has been received. Notice to the Company shall be directed to Anne Lee Benedict, Chief Legal Officer, by email at legal@summit-materials.com or by telephone
at 303-515-5161. Notice to Indemnitee shall be directed to Indemnitee’s contact information on file with the Company’s Secretary or its Human Resources Department. 

Section 11. Nonexclusivity. The provisions for indemnification and advancement of expenses set forth in this Agreement
shall not be deemed exclusive of any other rights which Indemnitee may have under any provision of law, in any court in which a proceeding is brought, other agreements or otherwise, and Indemnitee’s rights hereunder shall inure to the benefit
of the heirs, executors and administrators of Indemnitee. No amendment or alteration of the Company’s Certificate of Incorporation or Bylaws or any other agreement shall adversely affect the rights provided to Indemnitee under this Agreement.

 Section 12. No Construction as Employment Agreement. Nothing contained herein shall be construed as giving
Indemnitee any right to be retained as a director of the Company or in the employ of the Company. For the avoidance of doubt, the indemnification and advancement of expenses provided under this Agreement shall continue as to the Indemnitee even
though he may have ceased to be a director, officer, employee or agent of the Company. 

  
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 Section 13. Interpretation of Agreement. It is understood that the parties
hereto intend this Agreement to be interpreted and enforced so as to provide indemnification to Indemnitee to the fullest extent now or hereafter permitted by the DGCL. 

Section 14. Entire Agreement. This Agreement and the documents expressly referred to herein constitute the entire
agreement between the parties hereto with respect to the matters covered hereby, and any other prior or contemporaneous oral or written understandings or agreements with respect to the matters covered hereby are expressly superseded by this
Agreement. 
 Section 15. Modification and Waiver. No supplement, modification, waiver or amendment of this Agreement
shall be binding unless executed in writing by both of the parties hereto. No waiver of any of the provisions of this Agreement shall be deemed or shall constitute a waiver of any other provision hereof (whether or not similar) nor shall such waiver
constitute a continuing waiver. For the avoidance of doubt, this Agreement may not be terminated by the Company without Indemnitee’s prior written consent. 

Section 16. Successor and Assigns. All of the terms and provisions of this Agreement shall be binding upon, shall
inure to the benefit of and shall be enforceable by the parties hereto and their respective successors, assigns, heirs, executors, administrators and legal representatives. The Company shall require and cause any direct or indirect successor
(whether by purchase, merger, consolidation or otherwise) to all or substantially all of the business or assets of such Indemnitor, by written agreement in form and substance reasonably satisfactory to Indemnitee, expressly to assume and agree to
perform this Agreement in the same manner and to the same extent that the Company would be required to perform if no such succession had taken place. 

Section 17. Service of Process and Venue. The Company and Indemnitee hereby irrevocably and unconditionally
(i) agree that any action or proceeding arising out of or in connection with this Agreement shall be brought only in the Chancery Court of the State of Delaware (the “Delaware Court”), and not in any other state or federal court in
the United States of America or any court in any other country, (ii) consent to submit to the exclusive jurisdiction of the Delaware Court for purposes of any action or proceeding arising out of or in connection with this Agreement,
(iii) appoint, to the extent such party is not otherwise subject to service of process in the State of Delaware, irrevocably Corporation Service Company, 2711 Centerville Road, Suite 400, Wilmington, Delaware 19808 as its agent in the State of
Delaware as such party’s agent for acceptance of legal process in connection with any such action or proceeding against such party with the same legal force and validity as if served upon such party personally within the State of Delaware,
(iv) waive any objection to the laying of venue of any such action or proceeding in the Delaware Court, and (v) waive, and agree not to plead or to make, any claim that any such action or proceeding brought in the Delaware Court has been
brought in an improper or inconvenient forum. 
 Section 18. Governing Law. This Agreement shall be governed by and
construed in accordance with the laws of the State of Delaware. If a court of competent jurisdiction shall make a final determination that the provisions of the law of any state other than Delaware govern indemnification by the Company of
Indemnitee, then the indemnification provided under this Agreement shall in all instances be enforceable to the fullest extent permitted under such law, notwithstanding any provision of this Agreement to the contrary. 

  
 8 

 Section 19. Counterparts. This Agreement may be executed in two or
more counterparts, each of which shall be deemed to be an original and all of which together shall be deemed to be one and the same instrument, notwithstanding that both parties are not signatories to the original or same counterpart. 

Section 20. Headings. The section and subsection headings contained in this Agreement are for reference purposes
only and shall not affect in any way the meaning or interpretation of this Agreement. 

  
 9 

 This Agreement has been duly executed and delivered to be effective as of the date first above
written. 
  

							
	Company:	 	Indemnitee:
		
	SUMMIT MATERIALS, INC.	 	
				
	By:	 	  
	 		 	  

	Name:	 		 	Name:
	Title:	 		 	Title:

 [Summit – Signature Page to Indemnification Agreement]

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