POWER OF ATTORNEY

     Know all by these presents, that the undersigned hereby constitutes and
appoints each of Mark A. Hershey and Bryan Y.M. Tham of Armstrong World
Industries, Inc. or any of them signing singly, and with full power of
substitution, the undersigned's true and lawful attorney-in- fact to:

     1.   prepare, execute in the undersigned's name and on the
          undersigned's behalf, and submit to the U.S. Securities and Exchange
          Commission (the "SEC") a Form ID, including amendments thereto, and
          any other documents necessary or appropriate to obtain codes and
          passwords enabling the undersigned to make electronic filings with the
          SEC of reports required by Section 16(a) of the Securities Exchange
          Act of 1934 or any rule or regulation of the SEC;

     2.   take any other action of any type whatsoever in connection with
          the foregoing which, in the opinion of such attorney-in-fact, may be
          of benefit to, in the best interest of, or legally required by, the
          undersigned, it being understood that the documents executed by such
          attorney-in-fact on behalf of the undersigned pursuant to this Power
          of Attorney shall be in such form and shall contain such terms and
          conditions as such attorney-in-fact may approve in such attorney-in-
          fact's discretion.

     The undersigned hereby grants to each such attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary, or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney-in-fact, or such
attorney-in- fact's substitute or substitutes, shall lawfully do or cause to be
done by virtue of this power of attorney and the rights and powers herein
granted. The undersigned acknowledges that the foregoing attorneys-in-fact, in
serving in such capacity at the request of the undersigned, are not assuming any
of the undersigned's responsibilities to comply with Section 16 of the
Securities Exchange Act of 1934.

     This Power of Attorney shall remain in full force and effect unless revoked
by the undersigned in a signed writing delivered to the foregoing
attorneys-in-fact.

     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 1st day of April, 2016.




                                   /s/ Stephen McNamara
                                   ------------------------------
                                   Name:  Stephen McNamara