Modified Bitumen

Modified bitumen (modbit) membranes are hybrids that incorporate the hig- tech formulation and prefabrication advantages of single-ply with some of the traditional installation techniques used in built-up roofing. These materials are factory-fabricated layers of asphalt, “modified” using a rubber or plastic ingredient for increased flexibility, and combined with reinforcement for added strength and stability. There are two primary modifiers used today: APP (atactic polypropylene) and SBS (styrene butadiene styrene).

• Self-adhered modbit has an adhesive backing that allows the installer to peel the release film and stick the membrane to the substrate. These systems usually consist of 2 layers – a base sheet and cap sheet.
• Torch applied modbit is installed by heating the asphalt on the back of the sheet until it becomes molten while rolling the sheet out. As the molten asphalt cools, the membrane bonds to the substrate. These systems usually consist of two to three layers including a base and cap sheet and or an interplay sheet for added reinforcement.
• Hot mop applications are installed by “mopping” a layer of hot asphalt onto the substrate while rolling the membrane into place. The asphalt or coal tar is heated in a kettle or tanker and then applied by mop. These systems usually consist of two to three layers including a base and cap sheet and/or an interplay sheet for added reinforcement.