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Exhibit No. 21

Subsidiaries of Armstrong World Industries, Inc.

December 31, 2025

The following is a list of subsidiaries of Armstrong World Industries, Inc., omitting certain subsidiaries, which, when considered in the aggregate as a single subsidiary, would not constitute a significant subsidiary.

 

U.S. Subsidiaries

Jurisdiction of

Incorporation

3form, LLC

Delaware

Architectural Components Group, Inc.

Delaware

Arktura LLC

Delaware

Armstrong Cork Finance LLC

Delaware

Armstrong Ventures, Inc.

Delaware

Armstrong World Industries (Delaware) LLC

Delaware

Armstrong World Industries Canada Ltd.

Canada

AWI Licensing Company

Delaware

Tectum, Inc.

Delaware

Turf Design, Inc.

Illinois