This is capable of spans up to 12 m and can be designed to accommodate many different pitch angles.įor more information see: Trussed rafters This consists of a rafter incorporating tension and compression members in the shape of a W. In modern house construction, the most common form of rafter is known as the fink or 'w' trussed rafter. By installing a purlin into the roof structure, rafters no longer needed to be as thick and heavy, allowing larger potential spans. These run perpendicular to rafters, providing additional stiffness. In order to increase potential roof spans without compromising wall stability, increasing rafter sizes or attracting extra costs, purlins were introduced. The rafters sit on a wall plate which is an efficient means of spreading the load exerted by the roof structure down through the walls without creating pressure points where each rafter meets the wall.Ī closed couple roof adds ceiling joists running horizontally between the rafter feet, to support a ceiling and to make the structure much more rigid. The couple roof comprises two rafters leaning against each other, tied where they meet at the top.
Rafters can be used as a key component of various types of roof design. The may have battens laid on top of and perpendicular to them, to fix the roof covering to. Rafters are typically made of timber or steel and can be concealed within the roof structure, or can be left exposed to the spaces below. Rafters are generally laid in series, side by side, providing a base to support roof decks, roof coverings and so on. Typically, it runs from the ridge or hip of the roof to the wall plate of the external wall. A rafter is a structural component that is used as part of a roof construction.
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