POWER OF ATTORNEY
                      FOR SECTION 16 REPORTING OBLIGATIONS

     KNOW ALL BY THESE PRESENTS, that the undersigned hereby makes, constitutes
and appoints James F. Major, Jr., Lanesha T. Minnix and Jason Ritter signing
singly, as the undersigned's true and lawful attorney-in-fact, with full power
and authority as hereinafter described on behalf of and in the name, place and
stead of the undersigned to:

(1)  prepare, execute, acknowledge, deliver and file Forms 3, 4, and 5
     (including any amendments thereto) with respect to the securities of BMC
     Stock Holdings, Inc., a Delaware corporation, or any successor thereto (the
     "Company"), with the U.S. Securities and Exchange Commission, any national
     securities exchanges and the Company, as considered necessary or advisable
     under Section 16(a) of the Securities Exchange Act of 1934 and the rules
     and regulations promulgated thereunder, as amended from time to time (the
     "Exchange Act");

(2)  seek or obtain, as the undersigned's representative and on the
     undersigned's behalf, information of transactions in the Company's
     securities from any third-party, including brokers, employee benefit plan
     administrators and trustees, and the undersigned hereby authorizes any such
     person to release any such information to the undersigned and approves and
     ratifies any such release of information; and

(3)  perform any and all other acts which in the discretion of such attorney-in-
     fact is necessary or desirable for and on behalf of the undersigned in
     connection with the foregoing.

The undersigned acknowledges that:

(1)  this Power of Attorney authorizes, but does not require, such attorney-in-
     fact to act in his or her discretion on information provided to such
     attorney-in-fact without independent verification of such information;

(2)  any documents prepared and/or executed by such attorney-in-fact on behalf
     of the undersigned pursuant to this Power of Attorney will be in such form
     and will contain such information and disclosure as such attorney-in-fact,
     in his or her discretion, deems necessary or desirable;

(3)  neither the Company nor such attorney-in-fact assumes (i) any liability for
     the undersigned's responsibility to comply with the requirement of the
     Exchange Act, (ii) any liability of the undersigned for any failure to
     comply with such requirements, or (iii) any obligation or liability of the
     undersigned for profit disgorgement under Section 16(b) of the Exchange
     Act; and

(4)  this Power of Attorney does not relieve the undersigned from responsibility
     for compliance with the undersigned's obligations under the Exchange Act,
     including without limitation the reporting requirements under Section 16 of
     the Exchange Act.

     The undersigned hereby gives and grants the foregoing attorney-in-fact full
power and authority to do and perform all and every act and thing whatsoever
requisite, necessary or appropriate to be done in and about the foregoing
matters as fully to all intents and purposes as the undersigned might or could
do if present, hereby ratifying all that such attorney-in-fact of, for and on
behalf of the undersigned, shall lawfully do or cause to be done by virtue of
this Power of Attorney.

     This Power of Attorney shall remain in full force and effect until revoked
by the undersigned in a signed writing delivered to such attorney-in-fact.


     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 5th day of October, 2017.


                           By:     /s/ Keith Costello
                           ---------------------------------------
                           Name:   Keith Costello
                           Title:  Senior Vice President of Sales and Marketing