Top roof water proofing: the proper design of falls in a flat roof is an essential consideration in the overall drainage of the roof. Falls create flow paths to direct the drainage of rain-water away from the roof to suitable discharge points. To be effective, it is essential to clear surface water as rapidly as possible from the flat roof to avoid pounding or stagnation of water on the roof itself. Waterproofing on a flat roof is a prime cause of deterioration because variation in temperature wet and dry areas of the roof can cause differential thermal movement together with the accumulation of acids left by evaporating rain, this would cause a breakdown on the roof surface.