Purlin Spacing For Metal Roofs

This will depend upon the type of panel that is used and the thickness of the steel.

Purlin spacing for metal roofs.

The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to. For the lighter material such as lightweight aluminum the common spacing length is 4 inches of clear gap. Load tables specifying safe loads for different spans are available from metal deck manufacturers. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.

Standard gage are generally used for roofing. Numbers 20 and 22 u s. By the standard the most used placement of purlin span for metal roof is five foot intervals. Wider panels allow for greater spacing between rafters.

To determine how far apart to set rafters measure the width of the metal panel and then the width of the first hill and valley of the panel. Spacing for purlins on a standard load most designs call for purlin placement at five foot intervals. Do all roofing projects require purlins. However it is important to note that expected load is a crucial factor while determining this.

If the space between posts is greater than 8 feet then brace is needed to avoid buckling. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. For 2x6s purlins the posts are spaced in 6 feet distance. The heavier the expected load is the shorter the distance between the purlins.

A metal roof must also allow for some overlap on each side of the panels which will reduce the effective width of the panel. The typical spacing standards for residential and commercial buildings are about 1 to 2 foot. The spacing of purlins on roofs and girts on wall is usually 4 to 6 ft. Screw line spacing for metal roofing over metal purlins.

For heavier material such as gage steel the metal roof purlins spacing length could go up to 4 feet. Purlins are 2 by 4 feet and are installed much like metal roofing. However engineering determines the optimal spacing between the purlins. We do recommend it however.

An engineer will use a load chart in order to determine the spacing between metal purlins.