Modified Bitumen

Modified Bitumen Roof Systems

Modified Bitumen Roof systems are similar to built-up roofs in that they involve a multi-ply assembly, but don’t require a gravel surface. The other difference is a material has been added to the asphalt sheets that “modify” their characteristics to weather better under normal climatic conditions. Specific types are called Asphaltic Polypropylene Polymers (APP) and Styrene-Butadiene-Styrene (SBS).

APP materials have been modified with a plastic component which encapsulates the asphalt molecules. Generally, APP products are smooth-surfaced and require some type of top surfacing to achieve a fire resistant rating, which is required by many building codes.

SBS materials have been modified with a rubber-like synthetic material, which becomes part of the asphalt molecule and changes its characteristics. SBS products generally come with a granule surfacing and a fire retardant to achieve a fire resistant rating.

A.D. Willis Company has been named a U.S. Intec “All Star Platinum Contractor” for our commitment to perfection in applying their modified bitumen roof system.