Repair Technique for Buckled Wood Truss Members

Abstract

Many examples of wood roof trusses built in the early 1900’s still exist today. The compression members were often composed of built-up, vertically laminated lumber sections inadequately tied together and often laterally unbraced for substantial distances. Delaminations due to seasonal swelling and shrinkage forced the pieces to behave individually. The resulting overstresses initiated lateral buckling which became amplified by creep in the wood over an extended period of time. The roof surface warps and tears; moisture enters, and evidence of a problem finally becomes visible. Serviceability, and more importantly, safety, is threatened. A relatively unknown repair technique to permanently straighten and strengthen bowed and fractured truss compression members utilizes structural steel shapes to clamp and squeeze out the bow. A series of 1911 wood scissors trusses which were fractured and near collapse, were recently saved by this technique. The primary advantages of this repair method are simplicity, economy, avoidance of roof removal, and minimal intrusion on the original esthetics.