Modified Bitumen Roof Systems – (MBs) consist of one, two, or three-ply systems with modifiers, such as APP or SBS (Styrene Butadiene Styrene), which adds plastic or rubber-like properties to increase durability and strength. APP is adhered using heat and SBS with adhesive, both are reinforced with fiberglass or polypropylene. The type of substrate will typically determine the type of system being installed. Modified membranes may also be installed in conjunction with a built-up roof to form a “hybrid” roof system. MBs have proven performance on residential, commercial, and industrial applications.