Purlin Spacing For Steel Roofing

If the space between posts is greater than 8 feet then brace is needed to avoid buckling.

Purlin spacing for steel roofing.

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. For heavier material such as gage steel the metal roof purlins spacing length could go up to 4 feet. For the lighter material such as lightweight aluminum the common spacing length is 4 inches of clear gap.

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. By the standard the most used placement of purlin span for metal roof is five foot intervals. Purlin spacing for metal roofing. Spacing for purlins on a standard load most designs call for purlin placement at five foot intervals.

However engineering determines the optimal spacing between the purlins. Fyi we run purlins on 3 5 feet on center depending on size of purlin. 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.

For 2x4s purlins the posts are spaced in 4 feet distance. We do recommend it however. This will depend upon the type of panel that is used and the thickness of the steel. Once the purlin spacing is determined then the metal roofing panels are typically attached to every line of purlins.

The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed. An engineer will use a load chart in order to determine the spacing between metal purlins. The heavier the expected load is the shorter the distance between the purlins. Screw line spacing for metal roofing over metal purlins.

Do all roofing projects require purlins. For 2x6s purlins the posts are spaced in 6 feet distance. Spacing is typically 24 on center in low snow loads and is reduced based upon truss span and snow load.