The dead load of a building of light frame construction is about 10 lb/ft.2 for a flooring or roofing system without plastered ceilings and 20 lb/ft.2 with plastered ceilings. For a concrete flooring system, each 1 in. thick slab has a uniform load of about 12 psf; this is 36 psf for a 3 in. slab. To this, at least 10 psf should be added for the supporting system. Dead loads are gravity forces that act vertically downward. On a sloped roof, the dead load acts over the entire inclined length of the member.