Flat roof systems work by providing a waterproof membrane over a building. They consist of one or more layers of hydrophobic material placed over a structural deck with
a vapor barrier typically placed between the deck and roof membrane. Flashing, thin strips of material such as copper, intersect with the membrane and other building components (such as the parapet
walls) to prevent water infiltration.
Water is directed to drains, downspouts, and gutters by the slight pitch of the roof.