Rafter on roof is basically structural member which supports the roof. Based on its location, they have been classified into various categories.
Also Read: Basic Elements of Roof
A rafter is one of a series of sloped structural members (beams) that extend from the ridge or hip to the wall plate, downslope perimeter or eave, and that are designed to support the roof deck and its associated loads. A pair of rafters is a couple.
They are defined as the members of roof making up the main body of the framework. Roof Rafters are inclined members of a roof. Their sizes depend upon the length and spacing. The top of the rafter is fastened in one of the many ways determined by the type of roof. The bottom of the rafter rests on the plate member which is providing a connecting link between the wall and the roof. They are the functional parts of both the walls and the roof. There are many types of rafter for roofs depending on their location, shape and size.
A rafter that runs at right angles from the top of the wall plate to the roof ridge. These are the inclined members supporting the battens to support roof coverings. They are normally spaced at 30 to 45cm centre-to-centre, depending upon the roof covering material.
02. Hip Rafter:
The structural members of the roof at the intersection of two roof surfaces forming a hip are known as a hip rafter. These rafters run diagonally from the ridge to the corners of the walls support roof covering. Hip rafters also run at 45 degrees to the common rafters.
03. Hip Jack Rafter:
These rafters are shorter than the common rafters running from a hip to the eaves or from a ridge to the valley, and cut against the hip or ridge. Jack rafters cannot extend the full distance from plate to ridge board. Jack rafters are subdivided into hip and valley. In Hip jack rafters, the lower ends rest on the plate and the upper ends rest on a hip rafter.
04. Valley Rafter:
A valley is the reverse of a hip. It is formed by the intersection of two roof surfaces having an external angle is less than 180 degrees.
Valley Jack Rafter:
Valley jack rafter is the part of valley rafters. In valley jack rafters, lower ends rest on the valley rafters and the upper ends rest on the ridge board.