UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13D
Under the Securities and Exchange Act of 1934

(Amendment No. 1)

Armstrong World Industries, Inc.
(Name of Issuer)

Common Stock
(Title of Class of Securities)

04247X102
(CUSIP Number)

Allison Bennington, Esq.
ValueAct Capital
One Letterman Drive, Building D, Fourth Floor
San Francisco, CA 94129
(415) 362-3700
(Name, address and telephone number of Person
Authorized to Receive Notices and Communications)

Allison Bennington, Esq.
ValueAct Capital
One Letterman Drive, Building D, Fourth Floor
San Francisco, CA 94129
(415) 362-3700

December 15, 2014
(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box [ ].

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 240.13d-7 for other parties to whom copies are to be sent.

*The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

This information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).


SCHEDULE 13D

--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 2 of 14
-----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   ValueAct Capital Master Fund, L.P.
-----------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

-----------------------------------------------------------------------------
4. SOURCE OF FUNDS (See Instructions)*

   WC*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                         [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   British Virgin Islands
-----------------------------------------------------------------------------
                    7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES           8.  SHARED VOTING POWER
   BENEFICIALLY         9,200,000**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH      9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        9,200,000**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    9,200,000**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

   16.8%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    PN
-----------------------------------------------------------------------------
*See Item 3
**See Item 2 and 5


SCHEDULE 13D

--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 3 of 14
----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   VA Partners I, LLC
-----------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

-----------------------------------------------------------------------------
4. SOURCE OF FUNDS*

   00*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                         [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   Delaware
-----------------------------------------------------------------------------
                    7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES           8.  SHARED VOTING POWER
   BENEFICIALLY         9,200,000**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH      9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        9,200,000**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    9,200,000**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    16.8%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    00 (LLC)
-----------------------------------------------------------------------------
*See Item 3
**See Item 2 and 5


SCHEDULE 13D

--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 4 of 14
----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   ValueAct Capital Management, L.P.
-----------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

-----------------------------------------------------------------------------
4. SOURCE OF FUNDS*

   00*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                         [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   Delaware
-----------------------------------------------------------------------------
                    7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES           8.  SHARED VOTING POWER
   BENEFICIALLY         9,200,000**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH      9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        9,200,000**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    9,200,000**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    16.8%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    PN
-----------------------------------------------------------------------------
*See Item 3
**See Item 2 and 5


SCHEDULE 13D

--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 5 of 14
----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   ValueAct Capital Management, LLC
-----------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

-----------------------------------------------------------------------------
4. SOURCE OF FUNDS*

   00*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                         [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   Delaware
-----------------------------------------------------------------------------
                    7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES           8.  SHARED VOTING POWER
   BENEFICIALLY         9,200,000**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH      9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        9,200,000**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    9,200,000**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    16.8%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    00 (LLC)
-----------------------------------------------------------------------------
*See Item 3
**See Item 2 and 5


SCHEDULE 13D

--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 6 of 14
-----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   ValueAct Holdings, L.P.
---------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

---------------------------------------------------------------------------
4. SOURCE OF FUNDS*

   00*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                         [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   Delaware
-----------------------------------------------------------------------------
                    7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES           8.  SHARED VOTING POWER
   BENEFICIALLY         9,200,000**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH      9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        9,200,000**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    9,200,000**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    16.8%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    PN
-----------------------------------------------------------------------------
*See Item 3
**See Items 2 and 5


SCHEDULE 13D

--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 7 of 14
-----------------------------------------------------------------------------
1. NAME OF REPORTING PERSON/S.S. OR I.R.S. INDENTIFICATION NO. OF ABOVE
   PERSON (entities only)

   ValueAct Holdings GP, LLC
---------------------------------------------------------------------------
2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                  (a) [X]
                                                                      (b) [ ]
-----------------------------------------------------------------------------
3. SEC USE ONLY

-----------------------------------------------------------------------------
4. SOURCE OF FUNDS*

   00*
-----------------------------------------------------------------------------
5. CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
   PURSUANT TO ITEMS 2(d) or 2(e)                                        [ ]
-----------------------------------------------------------------------------
6. CITIZENSHIP OR PLACE OF ORGANIZATION

   Delaware
-----------------------------------------------------------------------------
                   7.  SOLE VOTING POWER
                        0
   NUMBER OF       ----------------------------------------------------------
   SHARES          8.  SHARED VOTING POWER
   BENEFICIALLY        9,200,000**
   OWNED BY EACH   ----------------------------------------------------------
   PERSON WITH     9.  SOLE DISPOSITIVE POWER
                        0
                   ----------------------------------------------------------
                   10.  SHARED DISPOSITIVE POWER
                        9,200,000**
-----------------------------------------------------------------------------
11. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

    9,200,000**
-----------------------------------------------------------------------------
12. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
    CERTAIN SHARES                                                        [ ]
-----------------------------------------------------------------------------
13. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

    16.8%
-----------------------------------------------------------------------------
14. TYPE OF REPORTING PERSON

    00 (LLC)
-----------------------------------------------------------------------------
*See Item 3
**See Items 2 and 5


--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 8 of 14
-----------------------------------------------------------------------------
THE PURPOSE OF THIS AMENDMENT NO. 1 TO SCHEDULE 13D IS TO AMEND THE OWNERSHIP
REPORTS OF THE REPORTING PERSONS AND TO AMEND ITEM 4(PURPOSE OF TRANSACTION),
ITEM 6 (CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
TO SECURITIES OF THE ISSUER), AND ITEM 7 (MATERIAL TO BE FILED AS EXHIBITS).
THE INFORMATION BELOW SUPPLEMENTS THE INFORMATION PREVIOUSLY PROVIDED.

Item 1.     Security and Issuer

       This Schedule 13D relates to the Common Stock (the "Common Stock") of
Armstrong World Industries, Inc., a Pennsylvania corporation (the "Issuer").
The address of the principal executive offices of the Issuer is 2500 Columbia
Avenue, Lancaster, Pennsylvania 17603.

Item 2.     Identity and Background

       This statement is filed jointly by (a) ValueAct Capital Master Fund,
L.P. ("ValueAct Master Fund"), (b) VA Partners I, LLC ("VA Partners I"), (c)
ValueAct Capital Management, L.P. ("ValueAct Management L.P."), (d) ValueAct
Capital Management, LLC ("ValueAct Management LLC"), (e) ValueAct Holdings,
L.P. ("ValueAct Holdings") and (f) ValueAct Holdings GP, LLC ("ValueAct
Holdings GP")(collectively, the "Reporting Persons").

       ValueAct Master Fund is a limited partnership organized under the laws
of the British Virgin Islands.  It has a principal business address of One
Letterman Drive, Building D, Fourth Floor, San Francisco, CA 94129.

        VA Partners I is a Delaware limited liability company, the principal
business of which is to serve as the General Partner to ValueAct Master Fund.
It has a principal business address of One Letterman Drive, Building D,
Fourth Floor, San Francisco, CA 94129.

        ValueAct Management L.P. is a Delaware limited partnership which
renders management services to ValueAct Master Fund.  ValueAct Management LLC
is a Delaware limited liability company, the principal business of which is
to serve as the General Partner to ValueAct Management L.P.  Each has a
principal business address of One Letterman Drive, Building D, Fourth Floor,
San Francisco, CA 94129.

       ValueAct Holdings is a Delaware limited partnership and is the sole
owner of  the limited partnership interests of ValueAct Management L.P. and
the membership interests of ValueAct Management LLC and is the majority owner
of the membership interests of VA Partners I.  ValueAct Holdings GP is a
Delaware limited liability company, the principal business of which is to
serve as the General Partner to ValueAct Holdings.  Each has a principal
business address of One Letterman Drive, Building D, Fourth Floor, San
Francisco, CA 94129.

       (d) and (e). None of the entities or persons identified in this Item 2
has during the past five years been convicted of any criminal proceeding
(excluding traffic violations or similar misdemeanors), nor been a party to a
civil proceeding of a judicial or administrative body of competent judgment,
decree or final order enjoining future violations of, or prohibiting or
mandating activities subject to, federal or state securities laws or finding
any violation with respect to such laws.


--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 9 of 14
-----------------------------------------------------------------------------

Item 4.     Purpose of Transaction

        The following paragraphs supplement the information set forth in
Item 4 of Reporting Person's Schedule 13D dated July 31, 2014.

        On December 15, 2014, Armstrong World Industries, Inc. (the
"Company") announced that it entered into a Nomination and Shareholder
Agreement (the "Nomination Agreement") with ValueAct Capital Master Fund
L.P., VA Partners I, LLC, ValueAct Capital Management, L.P., ValueAct Capital
Management, LLC, ValueAct Holdings, L.P., ValueAct Holdings GP, LLC and
Gregory P. Spivy (collectively, the "ValueAct Group"). The ValueAct Group
currently beneficially owns approximately 17% of the Company's outstanding
common stock.

        Pursuant to the Nomination Agreement, the Company appointed Gregory
P. Spivy, a Partner at ValueAct Capital, as a member of the board of
directors of the Company (the "Board"), effective immediately. Mr. Spivy's
term will continue until the Company's 2015 annual meeting of shareholders,
at which time the Company has agreed to nominate Mr. Spivy for election to
the Board. However, if at any time the ValueAct Group ceases to own at least
7.5% of the outstanding common stock of the Company, Mr. Spivy will be
required to resign from the Board and the Company will no longer be required
to nominate Mr. Spivy for election at the 2015 annual meeting of
shareholders. Under the Nomination Agreement, the ValueAct Group is entitled
to nominate a mutually acceptable replacement in the event that Mr. Spivy no
longer serves as an Armstrong director during the term of the Nomination
Agreement, so long as the ValueAct Group continues to own at least 7.5% of
the Company's outstanding common stock.

        During the term of the Nomination Agreement, the ValueAct Group has
agreed, among other things, that it will not: (i) in any way participate in
any "solicitation" of proxies, or advise, encourage or influence any person
with respect to the voting of any securities of the Company with respect to
the election of individuals to the Board or approval of any shareholder
proposals; (ii) in any way participate in any group with any persons who are
not ValueAct affiliates with respect to the Company's securities; (iii)
acquire any beneficial or other ownership interest in more than 19% in the
aggregate of the shares of the Company's common stock outstanding at such
time; (iv) sell the securities of the Company to any person or entity that
would own more than 5% of the outstanding shares of the Company's common
stock following such transaction; (v) effect or seek to effect any tender or
exchange offer, merger, consolidation, acquisition, scheme, arrangement,
business combination, recapitalization, reorganization, sale or acquisition
of material assets, liquidation, dissolution or other extraordinary
transaction involving the Company; (vi) engage in any short sale or similar
derivative transaction related to the market price or value of the Company's
securities; (vii) call or seek to call any meeting of shareholders, nominate
any candidate to the Board, seek the removal of any member of the Board, seek
to act by written consent, or make a request for any shareholder list or
other Company books and records; (viii) support or make any proposal that
constitutes controlling, changing or influencing the Board or management of
the Company, any material change in the capitalization or dividend policy of
the Company, seeking to have the Company waive or amend its governance
documents, or causing any class of securities of the Company to become
eligible for deregistration; (ix) disparage the Company or affiliates thereof


--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 10 of 14
-----------------------------------------------------------------------------
or any of its current or former officers or directors; (x) make any public
disclosure, announcement or statement regarding a plan or proposal with
respect to the Company or take any action that could require the Company to
make any public disclosure; (xi) enter into any discussions negotiations,
agreements, or understandings with any third party with respect to any of the
foregoing; or (xii) request, directly or indirectly, any amendment or waiver
of the foregoing.

        The ValueAct Group also has agreed that it will: (i) vote in favor of
the Company's nominees to the board of directors at the Company's 2015 annual
meeting of shareholders; and (ii) vote in accordance with the Board's
recommendation with respect to any routine matters and the advisory vote on
executive compensation to be submitted for the approval of shareholders at
the 2015 annual meeting.

        The Nomination Agreement terminates on the earliest of: (i) the
Company's material breach of the Nomination Agreement that has not been cured
within thirty (30) days after receipt of notice of such breach; (ii) the date
immediately following the last day on which a shareholder of the Company may
timely give notice of its intent to bring a proposal for consideration at the
Company's 2016 annual meeting of shareholders; (iii) the date that is ninety
(90) days after the date any ValueAct designee ceases to be a member of the
Board; and (iv) a mutually agreed upon date.

        The foregoing summary of the Nomination Agreement is not complete and
is subject to, and qualified in its entirety by, the text of the Nomination
Agreement, a copy of which is attached as Exhibit 99.1 to the Issuer's
Current Report on Form 8-K dated December 15, 2014 and incorporated herein by
reference.

        In connection with the execution of the Nomination Agreement, the
Company entered into a Confidentiality Agreement with the members of the
ValueAct Group.

        On December 15, 2014, the Company issued a press release relating to
the appointment of Mr. Spivy to the Board, a copy of which is attached as
Exhibit 99.2 to the Issuer's Current Report on Form 8-K dated December 15,
2014 and is incorporated herein by reference.

Item 5.    Interest in Securities of the Issuer

       (a) and (b).  Set forth below is the beneficial ownership of shares of
Common Stock of the Issuer for each person named in Item 2.  Shares reported
as beneficially owned by ValueAct Master Fund are also reported as
beneficially owned by (i) ValueAct Management L.P. as the manager of each
such investment partnership, (ii) ValueAct Management LLC, as General Partner
of ValueAct Management L.P., (iii) ValueAct Holdings, as the sole owner of
the limited partnership interests of ValueAct Management L.P. and the
membership interests of ValueAct Management LLC and as the majority owner of
the membership interests of VA Partners I and (iv) ValueAct Holdings GP, as
General Partner of ValueAct Holdings.  Shares reported as beneficially owned
by ValueAct Master Fund are also reported as beneficially owned by VA
Partners I, as General Partner of ValueAct Master Fund.  VA Partners I,
ValueAct Management L.P., ValueAct Management LLC, ValueAct Holdings and
ValueAct Holdings GP also, directly or indirectly, may own interests in one
or more than one of the partnerships from time to time.  Unless otherwise


--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 11 of 14
-----------------------------------------------------------------------------
indicated below, by reason of such relationship ValueAct Master Fund is
reported as having shared power to vote or to direct the vote, and shared
power to dispose or direct the disposition of, such shares of Common Stock,
with VA Partners I (only with respect to ValueAct Master Fund), ValueAct
Management L.P., ValueAct Management LLC, ValueAct Holdings and ValueAct
Holdings GP.

        As of the date hereof, ValueAct Master Fund is the beneficial owner
of 9,200,000 shares of Common Stock, representing approximately 16.8% of the
Issuer's outstanding Common Stock (which shares may also be deemed to be
beneficially owned by VA Partners I).

        ValueAct Management L.P., ValueAct Management LLC, ValueAct Holdings
and ValueAct Holdings GP may each be deemed the beneficial owner of an
aggregate of 9,200,000 shares of Common Stock, representing approximately
16.8% of the Issuer's outstanding Common Stock.

       All percentages set forth in this Schedule 13D are based upon the
Issuer's reported 54,888,401 outstanding shares of Common Stock as
reported in the Issuer's 10-Q for the quarterly period ended September 30,
2014.

       (c) The Reporting Persons have not made any transactions in the
Issuer's Common Stock in the sixty days prior to the date of this Report.

       (d) and (e)  Not applicable.

Item 6.     Contracts, Arrangements, Understandings or Relationships with
            Respect to Securities of the Issuer

       Other than as described elsewhere in this Report and as previously
reported, the Reporting Persons have no understandings, arrangements,
relationships or contracts relating to the Issuer's Common Stock which are
required to be described hereunder.

Item 7.     Material to Be Filed as Exhibits

(1) Joint Filing Agreement.

      (2) Nomination and Shareholder Agreement, dated December 15, 2014, by
and among the Issuer and the ValueAct Group, filed as Exhibit 99.1  to the
Issuer's Current Report on Form 8-K dated December 15, 2014 and incorporated
herein by reference.


--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 12 of 14
-----------------------------------------------------------------------------
                                  SIGNATURE
          After reasonable inquiry and to the best of his knowledge and
belief, the undersigned certifies that the information set forth in this
statement is true, complete and correct.

                              POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears
below on this Schedule 13D hereby constitutes and appoints Jeffrey W. Ubben,
Bradley E. Singer, G. Mason Morfit and Allison Bennington, and each of
them, with full power to act without the other, his or its true and lawful
attorney-in-fact and agent, with full power of substitution and
resubstitution, for him or it and in his or its name, place and stead, in any
and all capacities (until revoked in writing) to sign any and all amendments
to this Schedule 13D, and to file the same, with all exhibits thereto and
other documents in connection therewith, with the Securities and Exchange
Commission, granting unto said attorneys-in-fact and agents, and each of
them, full power and authority to do and perform each and every act and thing
requisite and necessary fully to all intents and purposes as he or it might
or could do in person, thereby ratifying and confirming all that said
attorneys-in-fact and agents or any of them, or their or his substitute or
substitutes, may lawfully do or cause to be done by virtue hereof.

                              ValueAct Capital Master Fund L.P., by
                              VA Partners I, LLC, its General Partner

                              By:     /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President

                              VA Partners I, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President


                               ValueAct Capital Management, L.P., by
                               ValueAct Capital Management, LLC its
                               General Partner

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President


                               ValueAct Capital Management, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President


--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 13 of 14
-----------------------------------------------------------------------------


                                ValueAct Holdings, L.P., by
                                ValueAct Holdings GP, LLC, its
                                General Partner

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President


                                 ValueAct Holdings GP, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President


--------------------------                          -------------------------
CUSIP NO. 04247X102                                             Page 14 of 14
-----------------------------------------------------------------------------
                                 Exhibit 1

                           JOINT FILING UNDERTAKING

The undersigned parties hereby agree that the Schedule 13D filed herewith
(and any amendments thereto) relating to the Common Stock of Armstrong World
Industries Inc., is being filed jointly on behalf of each of them with the
Securities and Exchange Commission pursuant to Section 13(d) of the
Securities Exchange Act of 1934, as amended.

                              ValueAct Capital Master Fund L.P., by
                              VA Partners I, LLC, its General Partner

                              By:     /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President

                              VA Partners I, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President


                               ValueAct Capital Management, L.P., by
                               ValueAct Capital Management, LLC its
                               General Partner

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President


                               ValueAct Capital Management, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President

                                ValueAct Holdings, L.P., by
                                ValueAct Holdings GP, LLC, its
                                General Partner

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President


                                 ValueAct Holdings GP, LLC

                              By:    /s/  Bradley E. Singer
                                --------------------------------------
Dated:  December 16, 2014     Bradley E. Singer, Vice President

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