Modified bitumen roofing systems are applied through a multi-step process involving the modification of asphalt with polymers, such as SBS (styrene-butadiene-styrene) or APP (atactic polypropylene). This enhances flexibility and durability. The modified bitumen is then manufactured into rolls, which can be installed using various methods, including torching, cold adhesive, or self-adhering techniques. Proper surface preparation and installation ensure optimal adhesion and performance, providing a robust waterproofing solution for flat and low-slope roofs.