Mod bit at 50

A roof system backbone continues to serve the industry well

For decades, polymer-modified bitumen has been a common roofing material used throughout North America. Installed using a torch, asphalt or cold adhesive, polymer-modified bitumen has been used for years by roofing contractors to build durable, weather-resistant low-slope roof systems.

As the material turns 50 years old, I'll review the product's history and preview what's ahead.


Following the long use of built-up roofing (BUR) worldwide, polymer-modified bitumen membranes were created as a soft polymer-asphalt mix identified as atactic polypropylene (APP) by Romolo Gorgati in Italy in 1967. By 1969, polymer-modified bitumen membranes were available in Germany, soon followed by most of Europe. After the oil embargo in 1973, skyrocketing petroleum prices drove the development of polymer-modified bitumen membranes in the U.S. However, these membranes did not come into prominence as a roofing product in the U.S. until the 1980s.