This week at work my crew was setting trusses for a new house and it reminded me about how often residential wood trusses collapse. The biggest reason they collapse is poor bracing and a mis-understanding about how to proper erect these great time savers. A typical metal plate connected wood truss is a very efficient way of framing a roof. The trusses are typically designed by a large wood truss manufacturer for the local building code required loads. The manufacturer than builds the trusses in a factory and delivers them to the job site with some kind of boom truck or crane.
One of the large companies designing wood trusses in this country is Alpine Engineered Products. The trusses in the picture were designed by them and then manufactured by a local lumber company that we use. Along with the set of engineered drawings comes some general information about bracing trusses. Because every situation is so different it’s up to the builder to understand the concepts and apply them correctly. Many times when a collapse has occurred the investigation reveals a lack of proper bracing.
Alpine Engineered Products publishes a great Builders Guide To Trusses. The guide has lots of information for builders about proper handling, connections, reading the drawings and bracing. One of the more important bracing issues is properly bracing the gable ends and then connecting that bracing to the laterals along the length of the building. The other important bracing is web braces that are actually detailed and called out on the drawings. Again the Builders Guide To Trusses is a big help understanding how that works.
So next time you’re involved with the erection of wood trusses or you’re having a new home built with trusses make sure that the trusses are properly braced.