Should a flat roof be sloped?
Sloping A Flat Roof
Sloping should be implemented if the structure causes the roof to pond water for an extended period of time. Water which evaporates within 48 to 72 hours is acceptable.
If standing water occurs for a prolonged period of time and additional drainage is not an option the roof should be sloped. Drainage should be added and all drains should be sumped when possible. Certain roofing system warranties require sloping.