Roof Truss Rafter And Purlin

The roof support system is a ridgepole and either rafters which run perpendicular from the top of the walls to the ridge or purlins which run parallel to the ridge.

Roof truss rafter and purlin.

The boards creating the slope of the roof are wider than lumber used to build trusses 2x8s 2x10s and 2x12s are most common in rafters vs. A purlin plate in wood construction is also called an arcade plate in european english under purlin and principal purlin. The term plate means a major horizontal supporting timber. In finished space insulation is placed between the rafter boards and drywall or other material is fastened to the face.

Purlin and rafter are the basic members of any roof structure. A truss roof using factory made trusses which are delivered to site complete and just erected. As structural members they resist loads and provide lateral restraints for truss members therefore it is important to design them properly against forces such as bending shear torsion buckling etc. Purlin plates are beams which support the mid span of rafters and are supported by posts.

Rafter boards are fastened to the ridge board at the peak and the top plate where they join the wall. By supporting the rafters they allow longer spans than the rafters alone. Parts of a traditional queen post roof truss. It is especially preferable to use in huge room that lacks trusses to create overhead effect despite the fact that trusses are used for practical purpose in the first place.

They are the load transmitting members of the steel roof. Under purlins were typically propped off internal walls. Purlins might be attached to rafters while rafter should support all laps and joins. There are three types of purlins in wood construction.

For example an 8 x 4 under purlin would support the center of a row of 6 x 2 rafters that in turn would support 3 x 2 roof purlins to which the roof cladding was fixed. In timber construction purlins are nailed to the rafter or supporting trusses while in steel roof construction they are welded or bolted to the rafters or trusses by the means of cleats. Purlin plates under purlin principal purlins and common purlins. The rafter and purlin spacing for metal roof must be fitted to support the whole.

In lightweight timber roof construction under purlins were used to support rafters over longer spans than the rafters alone could span. This is the right way to fix truss clips connecting the rafter and wall plate. A common arrangement is a rafter and purlin system which combines purlins and rafters. The longitudinal horizontal beam that is sitting on a post or the principal rafter of a truss and used to support common rafters.

A cut roof this is the traditional method of cutting the timber on site and building up the roof using rafters ridge boards joists and purlins etc the exact details being determined by the size of roof size of timbers etc.