A roof having an almost level surface, except for either being slightly convex, to allow drainage towards its edges, or slightly concave, allowing water to drain at the center of the roof.
A roof with a level surface.
A slightly sloped roof, usually with a tar and gravel cover. Most commercial buildings use this kind of roof.
A flat roof is a type of covering of a building. In contrast to the sloped form of a roof, a flat roof is horizontal or nearly horizontal. Materials that cover flat roofs should allow the water to run off freely from a very slight inclination.
Roofing material on a structure with a roof deck which has a slope of less than 1" rise in a 12" run.