Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
Blackstone Holdings II L.P.
  2. Issuer Name and Ticker or Trading Symbol
Summit Materials, Inc. [SUM]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) _____ Other (specify below)
(Last)
(First)
(Middle)
C/O THE BLACKSTONE GROUP L.P., 345 PARK AVENUE
3. Date of Earliest Transaction (Month/Day/Year)
08/11/2015
(Street)

NEW YORK, NY 10154
4. If Amendment, Date Original Filed(Month/Day/Year)
6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)
2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)
4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)
5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)
6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)
7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)
2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)
5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)
6. Date Exercisable and Expiration Date
(Month/Day/Year)
7. Title and Amount of Underlying Securities
(Instr. 3 and 4)
8. Price of Derivative Security
(Instr. 5)
9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)
10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)
11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
LP Units of Summit Materials Holdings L.P. (1) 08/11/2015   S(2)     13,739,945   (1)   (1) Class A Common Stock 13,739,945 (2) 30,781,057 (3) I See Footnotes (4) (9) (10) (11) (12) (13)
LP Units of Summit Materials Holdings L.P. (1) 08/11/2015   S(2)     2,896,494   (1)   (1) Class A Common Stock 2,896,494 (2) 6,488,901 (3) I See Footnotes (5) (9) (10) (11) (12) (13)
LP Units of Summit Materials Holdings L.P. (1) 08/11/2015   S(2)     261,315   (1)   (1) Class A Common Stock 261,315 (2) 585,415 (3) I See Footnotes (6) (9) (10) (11) (12) (13)
LP Units of Summit Materials Holdings L.P. (1) 08/11/2015   S(2)     22,143   (1)   (1) Class A Common Stock 22,143 (2) 49,605 (3) I See Footnotes (7) (9) (10) (11) (12) (13)
LP Units of Summit Materials Holdings L.P. (1) 08/11/2015   S(2)     12,867   (1)   (1) Class A Common Stock 12,867 (2) 28,826 (3) I See Footnotes (8) (9) (10) (11) (12) (13)

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Blackstone Holdings II L.P.
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    
Blackstone Holdings I/II GP Inc
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    
Blackstone Group L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    
Blackstone Group Management L.L.C.
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    
SCHWARZMAN STEPHEN A
C/O THE BLACKSTONE GROUP L.P.
345 PARK AVENUE
NEW YORK, NY 10154
    X    

Signatures

 BLACKSTONE HOLDINGS II L.P., By: Blackstone Holdings I/II GP Inc., its general partner, By: /s/ John G. Finley, Name: John G. Finley, Title: Chief Legal Officer   08/13/2015
**Signature of Reporting Person Date

 BLACKSTONE HOLDINGS I/II GP INC., By: /s/ John G. Finley, Name: John G. Finley, Title: Chief Legal Officer   08/13/2015
**Signature of Reporting Person Date

 THE BLACKSTONE GROUP L.P., By: Blackstone Group Management L.L.C., its general partner, By: /s/ John G. Finley, Name: John G. Finley, Title: Chief Legal Officer   08/13/2015
**Signature of Reporting Person Date

 BLACKSTONE GROUP MANAGEMENT L.L.C., By: /s/ John G. Finley, Name: John G. Finley, Title: Chief Legal Officer   08/13/2015
**Signature of Reporting Person Date

 /s/ STEPHEN A. SCHWARZMAN   08/13/2015
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) Pursuant to the terms of an exchange agreement, dated as of March 11, 2015, limited partnership units of Summit Materials Holdings L.P. ("LP Units") held by the Reporting Persons are exchangeable for shares of the issuer's Class A common stock on a one-for-one basis.
(2) The Reporting Persons sold to the issuer the number of LP Units set forth above at a price per LP Unit of $24.784375, which represents the $25.75 price at which the issuer's Class A common stock was sold in a secondary offering, less the underwriters' discount of $0.965625 per share.
(3) Total holdings include LP Units previously reported as being indirectly beneficially owned by the Reporting Persons through Summit Materials Holdings GP, Ltd. ("Summit GP"). The Reporting Persons acquired direct ownership of such LP Units in connection with a dividend of LP Units by Summit GP, of which the Blackstone Funds (as defined below) are shareholders. The acquisitions were exempt under Rules 16a-9 and 16a-13.
(4) Reflects securities of the issuer held directly by Blackstone Capital Partners (Delaware) V-NQ L.P. (f/k/a Blackstone Capital Partners (Cayman) V-NQ L.P.).
(5) Reflects securities of the issuer held directly by Blackstone Capital Partners (Delaware) NQ V-AC L.P. (f/k/a Blackstone Capital Partners (Cayman) NQ V-AC L.P.).
(6) Reflects securities of the issuer held directly by Summit BCP Intermediate Holdings L.P. The general partner of Summit BCP Intermediate Holdings L.P. is Summit BCP Intermediate Holdings GP, Ltd. Summit BCP Intermediate Holdings GP, Ltd. is owned by Blackstone Capital Partners (Delaware) V-NQ L.P., Blackstone Capital Partners (Delaware) NQ V-AC L.P., Blackstone Family Investment Partnership (Delaware) V-NQ L.P. and Blackstone Participation Partnership (Delaware) V-NQ L.P.
(7) Reflects securities of the issuer held directly by Blackstone Family Investment Partnership (Delaware) V-NQ L.P. (f/k/a Blackstone Family Investment Partnership (Cayman) V-NQ L.P.).
(8) Reflects securities of the issuer held directly by Blackstone Participation Partnership (Delaware) V-NQ L.P. (f/k/a Blackstone Participation Partnership (Cayman) V-NQ L.P., and collectively with Blackstone Capital Partners (Delaware) V-NQ L.P., Blackstone Capital Partners (Delaware) NQ V-AC L.P., Summit BCP Intermediate Holdings L.P. and Blackstone Family Investment Partnership (Delaware) V-NQ L.P., the "Blackstone Funds").
(9) The general partner of each of Blackstone Capital Partners (Delaware) V-NQ L.P. and Blackstone Capital Partners (Delaware) NQ V-AC L.P. is Blackstone Management Associates (Cayman) V-NQ L.P. The general partners of each of Blackstone Management Associates (Cayman) V-NQ L.P., Blackstone Family Investment Partnership (Delaware) V-NQ L.P. and Blackstone Participation Partnership (Delaware) V-NQ L.P. are Blackstone LR Associates (Cayman) V-NQ Ltd. and BCP V-NQ GP L.L.C.
(10) Blackstone Holdings II L.P. is the sole member of BCP V-NQ GP L.L.C. and the controlling shareholder of Blackstone LR Associates (Cayman) V-NQ Ltd. The general partner of Blackstone Holdings II L.P. is Blackstone Holdings I/II GP Inc. The sole shareholder of Blackstone Holdings I/II GP Inc. is The Blackstone Group L.P. The general partner of The Blackstone Group L.P. is Blackstone Group Management L.L.C. Blackstone Group Management L.L.C. is wholly owned by Blackstone's senior managing directors and controlled by its founder, Stephen A. Schwarzman.
(11) Due to the limitations of the electronic filing system Blackstone Capital Partners (Delaware) V-NQ L.P., Blackstone Capital Partners (Delaware) NQ V-AC L.P., Summit BCP Intermediate Holdings L.P., Summit BCP Intermediate Holdings GP, Ltd., Blackstone Family Investment Partnership (Delaware) V-NQ L.P., Blackstone Participation Partnership (Delaware) V-NQ L.P., Blackstone Management Associates (Cayman) V-NQ L.P., BCP V-NQ GP L.L.C. and Blackstone LR Associates (Cayman) V-NQ Ltd. are filing a separate Form 4.
(12) Information with respect to each of the Reporting Persons is given solely by such Reporting Person, and no Reporting Person has responsibility for the accuracy or completeness of information supplied by another Reporting Person.
(13) Each of the Reporting Persons (other than the Blackstone Funds to the extent they directly hold securities reported herein), disclaims beneficial ownership of the securities held by the Blackstone Funds, except to the extent of such Reporting Person's pecuniary interest therein, if any, and, pursuant to Rule 16a-1(a)(4) under the Securities Exchange Act of 1934, each of the Reporting Persons (other than the Blackstone Funds to the extent they directly hold securities reported herein) states that the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of all of the reported securities for purposes of Section 16 or for any other purpose.

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