Rafter
![Common rafters without collar beams form most of this roof. There is not always a ridge board or beam where the rafter tops meet. Under the midsections of the rafters are purlins which support the common rafters and are supported by principal rafters. This roof ends in an octagonal hip.](/Images/godic/202501/18/Gin_gang_0071402.jpg")
![A double roof (using a Norman truss), common rafters supported by principal rafters (top chords in this case) and an unusual extra layer of common rafters on the lower half to form a gallerie. Note how the rafter poles for the gallerie tie-in. The Bequet-Ribault House was built c. 1793 near Ste. Geneviève, Missouri. It is one of five poteaux-en-terre buildings that survive in the US.[1]](/Images/godic/202501/18/Photograph_of_the_Roof_Framing_in_the_Bequet-Ribault_House_in_Ste_Genevieve_MO1402.png")
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![Coyau or sprocket. Labeled A](/Images/godic/202501/18/Coyaux1402.png")
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.