Purlin Spacing For Corrugated Metal Roofing

Without a set of blueprints with a pe s seal you have no option but to follow the inspectors gig.

Purlin spacing for corrugated metal roofing. The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. The support system for the roof is comprised of ridgepole and rafters or purlins. Once the purlin spacing is determined then the metal roofing panels are typically attached to every line of purlins. For heavier material such as gage steel the metal roof purlins spacing length could go up to 4 feet.

Purlin spacing is dependent on profile of the metal and gauge plus snow and wind load plus what the rafters are designed to carry. The typical spacing standards for residential and commercial buildings are about 1 to 2 foot. Screw line spacing for metal roofing over metal purlins this will depend upon the type of panel that is used and the thickness of the steel. 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.

An engineer will use a load chart in order to determine the spacing between metal purlins. You need to check the installation instructions from the manufacturer depending on whether the purlins firring strips are 1x or 2x material and how wide thickness metal gage of roofing steel or aluminum type of seams design wind and snow loading whether designed to be walked on or not etc i have seen it vary from as little as 4 inches clear gap between firring strips on lightweight aluminum to as much as 4 feet on very heavy gage steel standing seam roofing commonly around 1 2. We do recommend it however. When placing rafters for a tin roof also frequently referred to as corrugated metal or steel it is common to set the distance between rafters based on the size of the roofing panels.