X0304 4 2011-08-15 0 0000007431 ARMSTRONG WORLD INDUSTRIES INC AWI 0001017988 OCONNOR JAMES J C/O ARMSTRONG WORLD INDUSTRIES, INC. 2500 COLUMBIA AVENUE LANCASTER PA 17603 1 0 0 0 Common Stock 2011-08-15 4 P 0 2500 37.643 A 31987 D The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $37.63 to $37.65, inclusive. The reporting person hereby undertakes to provide to the issuer, any security holder of the issuer, or the staff of the Securities Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range stated herein. Includes 4,448 unvested restricted stock units. /s/ Robert J. Sandkuhler, Attorney-in-fact 2011-08-17