Page 1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K ( Mark One ) ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 2500 C TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 Pennsylvania ( State or other jurisdiction of incorporation or organization ) For the fiscal year ended December 31 , 2020 OR Title of each class Common Stock , $ 0.01 par For the transition period from ARMSTRONG WORLD INDUSTRIES , INC . ( Exact name of registrant as specified in its charter ) mbia Avenue , Lancaster , Pennsylvania ( Address of principal executive offices ) value per to Commission File Number 1-2116 Registrant's telephone number , including area code ( 717 ) 397-0611 Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol ( s ) AWI 23-0366390 ( I.R.S. Employer Identification No. ) 17603 ( Zip Code ) Name of each exchange on which registered New York Stock Exchange share Yes | No No 区 Yes Securities registered pursuant to Section 12 ( g ) of the Act : None Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes > No Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( $ 232.405 of this chapter ) during the preceding 12 months ( or for such shorter time period that the registrant was required to submit such files ) . Yes No Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company , or an emerging growth company . See the definitions of “ large accelerated filer , " " accelerated filer , " " smaller reporting company , ” and “ emerging growth company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer Non - accelerated filer Accelerated filer Smaller reporting company Emerging growth company If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . < No 区 Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Act ) . Yes ☐ The aggregate market value of the Common Stock of Armstrong World Industries , Inc. held by non - affiliates based on the closing price ( $ 77.96 per share ) on the New York Stock Exchange ( trading symbol AWI ) as of June 30 , 2020 was approximately $ 3.7 billion . As of February 17 , 2021 , the number of shares outstanding of the registrant's Common Stock was 47,788,314 . Documents Incorporated by Reference Certain sections of Armstrong World Industries , Inc.'s definitive Proxy Statement for use in connection with its 2021 annual meeting of shareholders , to be filed no later than April 30 , 2021 ( 120 days after the last day of our 2020 fiscal year ) , are incorporated by reference into Part III of this Form 10 - K Report where indicated .