rafter

A rafter is a sloped structural member that forms the main framework of a roof. It runs from the wall plate at the eave up to the ridge, and together with other rafters shapes the roof and transfers its loads to supporting walls or beams. Rafters are typically spaced at regular intervals and cut to seat securely on the wall plate and ridge.

Rafters come in several types. Common rafters run from the wall plate to the ridge; hip rafters extend from the building corner toward the ridge; jack rafters connect from hip rafters toward the ridge. Exterior ends may overhang as eaves, and the rafter tails extend beyond the walls. The end of a rafter can be notched (birdsmouth) to seat on the wall plate.

Roof framing may use a ridge board, which is non-structural, or a ridge beam, which carries part of the load. When a ridge beam is used, rafters bear against it; when only a ridge board is present, other members resist outward thrust. Materials include sawn timber, engineered wood products such as LVL or glulam, and occasionally steel.

Although roof trusses have largely replaced rafters in many new houses, rafters remain common in timber-frame and historic construction, where individual members are visible and repair is straightforward.