Built Up (BUR) and Modified Bitumen (Mod Bit) Roofing Systems
What is Bitumen?
Bitumen (sometimes referred to as pitch) is a thick, oily byproduct of crude oil refining or steel coaking.
What do these systems have in common?
Built-Up and Modified Bitumen systems share many characteristics, chief among them is the use of bitumen as an adhesive for layers of felt, fabric, or matting.
Built-Up Roofing Systems
Time tested, water resistant.
Built-Up roof systems are constructed with layers of felt and bitumen (either asphalt or coal tar pitch) that are applied hot and left to cool. They are then covered with gravel, a mineral sheet cap, or other weather resistant coatings. Generally, BUR systems are three or four ply. The layering of the bitumen and felt provide enhanced water resistance.
Modified Bitumen systems combine the layers of a BUR system during the manufacturing process rather than during the application process, creating a single-ply application. Polymer modifiers can be added during the manufacturing process to give the roof additional elasticity, temperature flexibility, and weatherability.