EXHIBIT NO. 5.1


          [Letterhead of Buchanan Ingersoll Professional Corporation]
 
                                       March 15, 1999
 
Board of Directors
Armstrong World Industries, Inc.
P.O. Box 3001
Lancaster, Pennsylvania  17604

Ladies and Gentlemen:

     We have acted as counsel to Armstrong World Industries, Inc., a
Pennsylvania corporation (the "Company"), in connection with the proposed
issuance by the Company of up to 300,000 shares of the Company's Common Stock,
par value $1.00 per share (the "Common Stock"), pursuant to the terms of the
Triangle Pacific Corp. Salaried Employees Profit Sharing Plan, the Triangle
Pacific Corp. Non-Union Hourly Employees 401(k) Plan, the Robbins Hardwood
Flooring, Inc. Employees' Retirement Savings Plan, the Hartco Flooring Company
Retirement Savings Plan and the Hartco Flooring Company Bargaining Employees'
Retirement Savings Plan, as proposed to be amended (collectively, the "Plans").
 
     In connection with such proposed issuance, we have examined the Articles of
Incorporation of the Company, as amended, the Bylaws of the Company, as amended,
the relevant corporate proceedings of the Company, the Registration Statement on
Form S-8 covering the issuance of such shares, and such other documents,
records, certificates of public officials, statutes and decisions as we consider
necessary to express the opinions contained herein.  In the examination of such
documents, we have assumed the genuineness of all signatures and the
authenticity of all documents submitted to us as originals and the conformity to
those original documents of all documents submitted to us as certified or
photostatic copies.

     Based on the foregoing, we are of the opinion that when the Registration
Statement shall have been declared effective by order of the Securities and
Exchange Commission and when the Common Stock has been duly issued and delivered
pursuant to the terms of the Plans, as amended, such shares of Common Stock will
be legally issued, fully paid and non-assessable.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                           Very truly yours,          
                                                                      
                                                                      
                                           BUCHANAN INGERSOLL         
                                           PROFESSIONAL CORPORATION   
                                                                      
                                           By:  /s/ Stephen W. Johnson 
                                                ----------------------
                                                Stephen W. Johnson