Architect George Woodward discusses the purpose of this in 1860: "The same amount of strength can be had with a less amount of lumber. Historically many rafters, including hip rafters, often tapered in height 1/5 to 1/6 of their width, with the larger end at the foot. Later, principal rafters and common rafters were mixed, which is called a major/minor or primary/secondary roof system. The earliest surviving roofs in Europe are of common rafters on a tie beam this assembly is known as a "closed couple". There are many names for rafters depending on their location, shape, or size (see below). In recent buildings there is a preference for trussed rafters on the grounds of cost, economy of materials, off-site manufacture, and ease of construction, as well as design considerations including span limitations and roof loads (weight from above). Exposed rafters are a feature of some traditional roof styles. In home construction, rafters are normally made of wood. Labeled AĪ rafter is one of a series of sloped structural members such as steel beams that extend from the ridge or hip to the wall plate, downslope perimeter or eave, and that are designed to support the roof shingles, roof deck, roof covering and its associated loads. Rafter and tie-beam joints (Carpentry and Joinery, 1925) Coyau or sprocket. It is one of five poteaux-en-terre buildings that survive in the US. Note how the rafter poles for the gallerie tie-in. 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. Under the midsections of the rafters are purlins which support the common rafters and are supported by principal rafters. There is not always a ridge board or beam where the rafter tops meet. Common rafters without collar beams form most of this roof. For other uses, see Rafter (disambiguation). This article is about the structural beam.
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