Sec Form 4 Filing - Graff Michael @ Builders FirstSource, Inc. - 2015-07-31

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 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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1. Name and Address of Reporting Person Graff Michael 2. Issuer Name and Ticker or Trading Symbol Builders FirstSource, Inc. [ BLDR] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O WARBURG PINCUS LLC, 450 LEXINGTON AVENUE 3. Date of Earliest Transaction (MM/DD/YY) 07/31/2015 (Street) NEW YORK, NY10017 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ 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 (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 Common Stock, par value $0.01 per share 07/31/2015 S 4,600,000 D $ 12.224 20,263,266 I ( 1 ) ( 2 ) See Footnote ( 1 ) ( 2 ) ( 3 )

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Graff Michael C/O WARBURG PINCUS LLC 450 LEXINGTON AVENUE NEW YORK, NY10017 X Signatures /s/ Michael Graff, Director 08/03/2015 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares of common stock, par value $0.01 per share (the "Common Stock"), of the Company that are reported herein are held by Warburg Pincus Private Equity IX, L.P., a Delaware limited partnership ("WP IX"). As of the date hereof, WP IX is the diret record holder of 20,263,266 shares of Common Stock of the Company. Warburg Pincus IX GP L.P., a Delaware limited partnership ("WP IX GP"), is the general partner of WP IX. WPP GP LLC, a Delaware limited liability company ("WPP GP"), is the general partner of WP IX GP. Warburg Pincus Partners, L.P., a Delaware limited partnership ("WP Partners"), is the sole member of WPP GP. Warburg Pincus Partners GP LLC, a Delaware limited liability company ("WP Partners GP"), is the general partner of WP Partners. Warburg Pincus & Co., a New York general partnership ("WP"), is the managing member of WP Partners GP. ( 2 )(Continued from Footnote 1) Warburg Pincus LLC, a New York limited liability company ("WP LLC"), manages WP IX. Charles R. Kaye and Joseph P. Landy are each Managing General Partners of WP and Managing Members and Co-Chief Executive Officers of WP LLC and may be deemed to control WP IX, WP IX GP, WPP GP, WP Partners, WP Partners GP, WP and WP LLC. By reason of the provisions of Rule 16a-1 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), WP IX GP, WPP GP, WP Partners, WP Partners GP, WP, WP LLC, Mr. Kaye and Mr. Landy may be deemed to be the beneficial owners of any securities that may be beneficially owned by WP IX. Each of WP IX GP, WPP GP, WP Partners, WP Partners GP, WP, WP LLC, Mr. Kaye and Mr. Landy disclaim beneficial ownership of all shares of Common Stock that may be deemed to be beneficially owned by WP IX, except to the extent of any indirect pecuniary interest therein. ( 3 )Michael Graff, the reporting person, who became a director of the Company on February 27, 2006, is a Partner of WP and a Managing Director and Member of WP LLC. As such, Mr. Graff may be deemed to have an indirect pecuniary interest (within the meaning of Rule 16a-1 of the Exchange Act) in an indeterminate portion of the securities reported as beneficially owned by WP IX, WP IX GP, WPP GP, WP Partners, WP Partners GP, WP and WP LLC. Mr. Graff disclaims beneficial ownership of such securities except to the extent of any indirect pecuniary interest therein. This Form 4 shall not be deemed an admission that any reporting person or any other person referred to herein is a beneficial owner of any securities of the Company for purposes of Section 16 of the Exchange Act, or for any other purpose or that any reporting person or other person has an obligation to file this Form 4.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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