This system was developed in the United States in the early seventies. The term modified refers to the addition of plastic or rubber-based polymeric binders to asphalt to improve its performance and durability. The special characteristics of mod-bit systems are in their toughness, light-weight loading, and resistance to wind and fire. They also provide an easily inspected surface and long-term service expectancy. Modified Bitumen roofing exhibits many characteristic of built-up, yet affords the ease of application of a single-ply system.
In effect, mod-bits exhibit properties of both built-up and single-ply roofing, yet it is a system which is complimentary in fulfilling specific roofing requirements that may not be met by B.U.R. or single-ply systems alone.