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A collar beam or collar is a horizontal member between two

rafter A rafter is one of a series of sloped structural members such as wooden 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 and its associate ...

s and is very common in domestic roof construction. Often a collar is structural but they may be used simply to frame a

ceiling A ceiling is an overhead interior surface that covers the upper limits of a room. It is not generally considered a structural element, but a finished surface concealing the underside of the roof structure or the floor of a story above. Ceilings ...

. A collar beam is often called a collar tie but this is rarely correct. A

tie Tie has two principal meanings: * Tie (draw), a finish to a competition with identical results, particularly sports * Necktie, a long piece of cloth worn around the neck or shoulders Tie or TIE may also refer to: Engineering and technology * ...

in building construction is an element in tension rather than compression and most collar beams are designed to work in compression to keep the rafters from sagging. A collar near the bottom of the rafters may replace a tie beam and be designed to keep the rafters from spreading, thus are in tension: these are correctly called a collar tie.

Etymology

''Collar'' in general comes from Latin ''collare'' meaning neck.

Collar beam roofs

The simplest form of roof framing is a common rafter roof. This roof framing has nothing but rafters and a tie beam at the bottoms of the rafters. The next step in the development of roof framing was to add a collar, called a collar beam roof. Collar beam roofs are suitable for spans up to around (4.5 meters).Moncrieff, G. K.. ''The principles of structural design'',. Chatham, Eng.: W. & J. Mackay & Co. orthe Royal Engineers Institute, 1897-98. Print.

Crown post roof framing

A crown post is a compression member, a post, in roof framing which carries a longitudinal beam called a crown plate. The crown plate in turn carries collar beams which help support and carry the rafters, thus collar beams are always found in crown post roof framing.

Arched brace roof

The arch brace truss is made by adding two braces between the rafters and collar. This puts the collar and the braces in tension.

References

{{Roofs Roofs