Roof

Roof, cover for the top of a building. A roof encloses and protects a building from the elements, and helps drain water from rainfall. Large beams (often called joists), timbers, and rafters support a roof. Metal, concrete, or composite materials are used to build a roof or smaller roofing units called shingles. Flat and lean-to roofs consist of designs of one flat plane. Roofs in which the design consists of two joined flat planes are the gable roof and its inverted design, the butterfly roof. The hip, gambrel, and mansard roofs are more sophisticated designs, in which more than two flat planes are joined at various angles. The design of the roof and the choice of roofing materials are based on the function of the building as well as the climate.