Purlins Of Flat Roofs

The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to.

Purlins of flat roofs.

Lay the first purlin at the ridge. Illustration shows purlins at 1 2m centres however the maximum purlin centres should not exceed 1 8m. Roof live load roof dead load x spacing x span of purlin 2 divided by. Image copyright belongs to albion sections limited uk roof purlin are members used to directly support roof sheeting materials and could be made of timber or steel.

How to install metal roof purlins. 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. Run a tape measure from end to end along the rafters of the roof to determine how many purlins will be needed for installation. If you are planning upon going with edgewise purlins across a single truss you are going to run into an uplift problem.

Purlins placed flat will not span eight feet so eliminates this option. Trusses most likely on 8 s. Or less x 1 1 cfu the flat use factor for applying the load to the wide face of a member. Snap a chalk line horizontally across the roof two feet down from the top.

8 x section modulus of a 4 2 of 1 3125 x fb fiberstress in bending x 1 15 duration of load x 1 15 cr repetitive member factor as the purlins are spaced 24 o c.