The flat roof is much more commonly seen on commercial buildings than on residences, but that doesn't mean it is without benefit for homeowners. Nonetheless, if the flat roof isn't constructed properly in all aspects, or if some of its ramifications are ignored, it can be the source of endless headaches. Let's look at some of the distinctions between a flat roof and a sloped roof and why one might be preferable to the other.
A flat roof, though graded enough to drain, must be watertight, whereas a sloped roof is designed not to be waterproof but water shedding. Any roof with a pitch less than 2 in 12 falls in the flat category, for the shedding principle fails below that steepness.