Modified bitumen (mod-bit) roofs consist of two plies of reinforced mod-bit membranes that are fused together with either liquid hot asphalt bitumen, thermofused with a blowtorch, or cold-applied with adhesives and hot air welded at the seams. Membrane reinforcement is either polyester or fiberglass-based. Mod-bit roofs have a granulated top surface that come in an array of colors. Application methods are often determined by the type of mod-bit membrane installed. There are two types of modified bitumen systems: APP and SBS.
Modified bitumen membranes gained prominence in Europe in the 1960s, and now have a significant share of the North American market. Modified bitumen is made of asphalt bitumen infused with either APP or SBS copolymers. Regular asphalt bitumen alone is hard and brittle at ambient temperatures, and even more so when cold. The introduction of these copolymers modifies these physical properties. APP (atactic polypropylene) is a plastic copolymer that enhances the properties of asphalt bitumen with flexibility, elasticity, and ductility. SBS (styrene- butadiene-styrene) is a rubber copolymer and endows the asphalt bitumen with even greater elasticity and flexibility at lower temperatures than its APP counterpart. The cold Canadian climate favours the use of SBS mod-bit.
HSX Roofing is a certified applicator of the following manufacturers’ Modified Bitumen systems: