felt-and-gravel roofing

built-up rib

A rib made of laminations of timber of various sizes.

built-up roofing, composition roofing, felt-and-gravel roofing, gravel roofing

built-up roofing
A continuous roof covering made up of laminations or plies of saturated or coated roofing felts, alternated with layers of asphalt or coal-tar pitch and surfaced with a layer of gravel or slag in a heavy coat of asphalt or coal-tar pitch or finished with a cap sheet; generally used on flat or low-pitched roofs. Also see tar-and-gravel roofing.