Rafter
A rafter is a sloped structural member that extends from the ridge of the roof down to the eave, supporting the roof sheathing and carrying roof loads (snow, wind, dead weight) down to the exterior walls. Rafters are the traditional roof framing method, cut individually and assembled on site. They create the basic triangular shape of a pitched roof.
In-Depth Explanation
Rafters are one of the oldest and most fundamental elements of wood construction, forming the skeletal framework of pitched roofs. Each rafter must be cut with three key geometric cuts: the plumb cut at the ridge (where it meets the ridge board or opposing rafter), the bird's mouth (the notch where it bears on the wall's top plate), and the tail cut (the angle at the eave end). Rafter sizing depends on span, spacing, species, grade, and the loads they must carry — building codes provide span tables that specify the maximum span for each size and spacing combination. Common residential rafter sizes range from 2x6 to 2x12, with 16 or 24 inches on-center spacing. While manufactured trusses have largely replaced site-built rafters in production housing because of their speed and engineered efficiency, conventional rafters remain essential for complex roof geometries, cathedral ceilings (where the rafter cavity is the insulation space), renovation work, and custom designs. A roof framed with rafters requires a ridge board or ridge beam at the peak, and the opposing rafters must be connected with collar ties or ceiling joists to resist the outward thrust they exert on the walls.
Usage Example
The framing crew cut and installed 32 pairs of 2x10 rafters at 16 inches on center to create the cathedral ceiling in the great room addition.