Rafter And Purlin Spacing For Metal Roof

Purlins should be fastened through the decking and into the rafters.

Rafter and purlin spacing for metal roof.

The metal roof purlins spacing must be done correctly within narrow tolerances. Fyi we run purlins on 3 5 feet on center depending on size of purlin. Contact fabral for additional information. Pole buildings with metal roofs are typically built with metal roofs resting directly on rafters and purlins horizontal members that run between rafters and tie them together.

We do recommend it however. The cos of the purlin spacing is because the load on the purlins is vertical and the purlin spacing is with the run of the roof. Wider panels allow for greater spacing between rafters. For more detailed information on re roofing applications consult fabral tech nical bulletin 721 re roofing with metal.

Without a set of blueprints with a pe s seal you have no option but to follow the inspectors gig. I explained the layout of roof trusses and purlins on your building design. Purlins are non pressure treated 1 x 4 x 12 lumber that is installed on to the roof in a specific layout pattern and screw pattern. The inspector asked about the type of wood being used as purlins.

Load tables are available for all fabral panels. I did not know. He gave me a copy of r802 5 1 3 rafter spans for common lumber species. There is a chance of damaging roofing sheets if you are failed to do so.

One of my questions was about snow loads. Because this roof design doesn t have the added weight of plywood roof sheathing and metal roofs are generally lighter than asphalt shingle roofs the rafters have much. This will provide a solid framework for attaching the metal panels. The table shows one 2 x 8 that will make a 15ft.

Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch. Purlin spacing is dependent on profile of the metal and gauge plus snow and wind load plus what the rafters are designed to carry. Rafter spacing is based on the width of the metal roofing panels. The wider the roofing panels the greater spacing distance you should put.

The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. Do all roofing projects require purlins. The width of metal panels will determine the rafter spacing. For sake of discussion we will assume a minimal roof snow load of 20 psf pounds per square foot and a 4 12 roof slope.