Several factors influence what constitutes a modified bitumen roof in asphalt or bitumen modification systems. These include the type of polymer used for modification, such as SBS (Styrene-Butadiene-Styrene) or APP (Atactic Polypropylene), which enhance flexibility and UV resistance. Additionally, the manufacturing process, including the method of blending and the thickness of the membrane, plays a crucial role. Environmental conditions, application techniques, and the intended use of the roofing system also significantly affect its performance and durability.