Modified Bitumen systems are similar to their BUR cousins, IE.: they come in two generic families. These types of systems are popular with clients that like the redundancy of a multi-ply roof assembly, but do not like a gravel surface roof, or are looking for something that is easier to maintain. The families are called "APP" and "SBS" types, and these names are acronyms for their chemical names. 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 basically encapsulates the asphalt molecules. SBS materials are modified with a rubber-like synthetic which in essence becomes part of the asphalt molecule and changes its characteristics. Generally speaking, APP products are smooth surfaced, and require some type of coating as a top surfacing to achieve a fire resistant rating which is required in many localities by building code. SBS products generally come with granule surfacing and a fire retardant in the product in order to achieve a fire resistant rated roof.

Modified Bitumen roof systems with quality installations performed by FixaRoof