One important defect that I find while inspecting houses with flat type roofs is the lack of adequate roof drains. When a flat roof system exists it is very important that the roof scupper drains remain obstruction free and free flowing because water will pool on the flat roof surface and infiltrate into the dwelling. Under the right climate conditions flat roofing systems have been known to collapse under snow and ice loads because of the lack of roof drainage. snow, ice and water collect until the roof structure buckles under the weight. It is imperative that a home inspector view the roof drains and determine if they are sufficient to properly drain the roof surface. A single drain is usually inadequate to propelry drain the roof surface. Additional drains and downspouts should be installed to pipe water off the surface and away from the home. Having a multiple drain system is a very good idea because if one drain were to be obstructed the other drain will pipe water away from the surface of the roof.