Modified bitumen systems combine the advantages of built-up roofing with the ease of application of a single-ply system. Bitumen is reinforced with fibreglass or polyester for added durability, and manufactured into sheets or rolls for ease of application. One, two (most common), or three ply-systems are available.
There are two kinds of modified bitumen systems:
- SBS (Styrene Butadiene Styrene) systems are usually installed with hot asphalts or cold adhesives.
- APP (Atactic Polypropylene) systems in almost every case are installed using the torch method.
The advantages of these systems are:
- Durable in extreme weather conditions
- Easy to repair
- Come in rolls for ease of application
- Factory-manufactured to ensure quality control
- Expand or contract with the movement of the building
- Variety of surfaces that resist oxidation and damage from UV rays.