Purlins For Roof Trusses

In architecture or structural engineering or building a purlin or purline is a horizontal structural member in a roof.

Purlins for roof trusses.

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. Trusses most likely on 8 s. Purlins 24 spacing mike the pole barn guru writes. If you are planning upon going with edgewise purlins across a single truss you are going to run into an uplift problem.

Purlins are dimensional lumber that are fastened to the top chord of trusses connecting them together for bracing purposes. 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. The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed. Purlins placed flat will not span eight feet so eliminates this option.

Purlins 24 oc are typical along with the bottom bracing shown. Spacing is typically 24 on center in low snow loads and is reduced based upon truss span and snow load. 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. To the good folks in michigan the only way to construct a pole building is to place the columns every eight feet.

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.