Guidelines for Use of Collar Beams

Abstract

Collar beams are used within triangular wooden roof structures as both ridge ties and rafter braces, in spite of the fact that specific recommendations for their use are often contradictory or imprecise. To develop more consistent and rational guidelines for the use of collar beams, a structural model of a triangular roof was subjected to various loading scenarios across a wide range of both roof slopes and collar beam locations. It was found that in regions of moderate or heavy snow, collars can effectively prevent rafter separation at the ridge; in regions of high wind and no snow, either metal ridge straps or collars placed directly at the ridge should be used for most roof configurations. When used as rafter braces to permit larger spans, collar beams can have a modest impact, but only within a limited range of roof angles.