Modified Bitumen Roofs

Lubbock Municipal Coliseum, Lubbock, Texas


Doctor's Hospital, Laredo, Texas

Modified Bitumen Roof systems are similar to Built-Up Roofs. These types of systems are popular with clients that like the redundancy of a multi-ply roof assembly that is easier to maintain, but not like a gravel roof surface. These types are called “APP” Asphaltic Polypropylene Polymers and “SBS” Styrene-Butadiene-Styrene. In either case, a material has been added to standard roofing asphalt to “modify” its characteristics to weather better under normal climactic conditions.

APP materials have been modified with a plastic material, which encapsulates the asphalt molecules. SBS materials are modified with a rubber-like synthetic material, which becomes part of the asphalt molecule and changes its characteristics.

Generally, APP products are smooth surfaced and require some type of coating as a top surfacing to achieve a fire resistant rating, which is required by many local building codes.

La Quinta, San Antonio, Texas

APP roofs are usually applied by heat welding the sheet to an insulation board.

SBS products generally come with granule surfacing and a fire retardant in the product in order to achieve a fire resistant rated roof, and are usually applied in a mopping of cold or hot asphalt to an insulation board. A. D. Willis Company, Inc. has been named by U.S. Intec as an “All Star Platinum Contractor” for our commitment to perfection and named Johns Manville as a "Blue Chip Contractor".

Modified Bitumen roof systems which A. D. Willis Company Inc. installs include:
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