Supporting Structure for Roof Trusses A structure that is not level and is out of square will result in an ugly and unsatisfactory roof line. Time is well spent in ensuring: The load bearing top plates are level. The structure is of the correct dimension The top plates as well as being level are straight in their length The internal walls are set below the outer wall level by: Unbattened ceiling – 10mm Battened ceiling – 10 mm plus batten thickness Roof Trusses Erection and Fixing It is convenient to mark the truss position on the wall plates before lifting trusses. Use the layout drawing as your guide and note that the truss design spacing must not be exceeded.   Ensure first truss is installed carefully and within erection tolerances.   WARNING – Do not use web as ladder to climb up or down the roof during installation. This can cause damage to the web and lead to serious injury.   Gable Roofs – Start with a gable truss at each end, fixing it to the top plate at the marked position. These trusses must be temporarily braced back to the ground or frame at the panel points.   Hip or Dutch Gable – Start with the Dutch girder truss or the truncated girder, placing it on the top plate at the position marked and temporarily bracing it back to the frame. Locate hip and jack trusses and adjust girder truss position before fixing.   Line – Using a stringline along the Apex, place each intermediate truss and fix it to the top plate at the position marked, spacing it with gauging rods and ties. Erection Bracing for Roof Trusses The roof trusses must be braced during erection. If this is not done, then two problems can occur.   Collapse during erection Erection tolerance will be exceeded, causing overloading, buckling and possible permanent damage. The exact details of erection bracing will, for practical purposes, differ from job to job. The following recommendations are for guidance only as the details employed are the erectors responsibility.   The first truss should be erected straight and plumb to erection tolerances given previously and temporarily braced to a rigid element, e.g. wall or ground.   The purpose of temporary bracing is to hold trusses straight and plumb prior to fixing permanent bracing. All permanent bracing, ties, hold down, etc. must be fixed prior to loading roof. Roof Trusses Frame Bracing The frame must be fully braced, plumb, and nailed home before the erection of trusses is commenced.