A flat roof cap sheet is a waterproof membrane that protects the roof structure from various environmental factors such as rain, snow, ultraviolet rays, and temperature fluctuations. Usually made from materials such as modified bitumen, EPDM (ethylene propylene diene monomer), or TPO (thermoplastic polyolefin), these sheets are designed to provide a robust barrier against moisture, prolonging the roof's lifespan and reducing maintenance costs.