APP waterproofing membrane (Atactic Polypropylene membrane) is a type of modified bitumen waterproofing material commonly used for flat roofs and concrete surfaces. It is made by blending bitumen with plastic (polypropylene) to enhance flexibility, durability, and resistance to heat and UV rays. Reinforced with polyester or fiberglass, APP membranes are applied using a torch-on method, creating a strong, seamless, and water-resistant layer ideal for long-term protection in harsh weather conditions.