Purlins For Roof Trusses

Purlins support the loads from the roof deck or sheathing and are supported by the principal rafters and or the building walls steel beams etc.

Purlins for roof trusses. Trusses most likely on 8 s. In post frame construction roof purlins are the members running the lengthwise direction of the building either placed on top of or between the roof trusses or rafters to attach the roof steel or other roof sheathing to. 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. Installation of pole barn purlins.

Purlins placed flat will not span eight feet so eliminates this option. 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. If you are planning upon going with edgewise purlins across a single truss you are going to run into an uplift problem. To strengthen the roof system truss clustering cross bracing and wind bracing is recommended at both end of the buildings and every 20 for longer span buildings.

Purlins are dimensional lumber that are fastened to the top chord of trusses connecting them together for bracing purposes. Purlins 24 oc are typical along with the bottom bracing shown. The use of purlins as opposed to closely spaced rafters is common in pre engineered metal building systems and both the ancient post and beam and newer pole building timber frame construction methodologies. In architecture or structural engineering or building a purlin or purline is a horizontal structural member in a roof.

Spacing is typically 24 on center in low snow loads and is reduced based upon truss span and snow load.