A modified bitumen roof is the next step in roofing systems that are designed to combine asphalt with polymerized rubber or plastic with fiberglass reinforcement to create a flexible waterproof membrane. This material is ideal for low-slop or flat roofing systems and can be applied as two-layer or multi-layered. They come in membrane form in rolls that are installed with an adhesive to the roof substrate. It can then be cold-adhered, heat welded, or self-adhered.

They are available in two forms, “plastic asphalt” aka atactic polypropylene (APP) or stands for styrene-butadiene-styrene (SBS) which is “elastic” or “rubberized” asphalt. There are several benefits to applying a modified bitumen roof as they are tear-resistant, waterproof, flexible, and energy-efficient.