Purlin Spacing For Metal Roofs

Screw line spacing for metal roofing over metal purlins.

Purlin spacing for metal roofs.

Standard gage are generally used for roofing. Numbers 20 and 22 u s. For 2x6s purlins the posts are spaced in 6 feet distance. Do all roofing projects require purlins.

An engineer will use a load chart in order to determine the spacing between metal purlins. Load tables specifying safe loads for different spans are available from metal deck manufacturers. By the standard the most used placement of purlin span for metal roof is five foot intervals. Metal roof purlins are installed horizontally under metal roofs.

This will depend upon the type of panel that is used and the thickness of the steel. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. The typical spacing standards for residential and commercial buildings are about 1 to 2 foot. Spacing for purlins on a standard load most designs call for purlin placement at five foot intervals.

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 heavier the expected load is the shorter the distance between the purlins. For the lighter material such as lightweight aluminum the common spacing length is 4 inches of clear gap. However it is important to note that expected load is a crucial factor while determining this.

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. They give added support to the roof and also provide a nailing surface for the end panels and drip edge. The spacing of purlins on roofs and girts on wall is usually 4 to 6 ft.

If the space between posts is greater than 8 feet then brace is needed to avoid buckling. 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. 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 purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to.

However engineering determines the optimal spacing between the purlins.