For 2x4s purlins the posts are spaced in 4 feet distance.
How far to space purlins steel roof.
80 screws for each roofing square.
For 2x6s purlins the posts are spaced in 6 feet distance.
The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed.
In this example the section of roof is 20 feet wide and 14.
Fyi we run purlins on 3 5 feet on center depending on size of purlin.
By the standard the most used placement of purlin span for metal roof is five foot intervals.
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.
Rather than having 2 4 purlins every 12 it would make far more sense economically to use 2 6 purlins every 24.
Spacing is typically 24 on center in low snow loads and is reduced based upon truss span and snow load.
For heavier material such as gage steel the metal roof purlins spacing length could go up to 4 feet.
Less expensive 1 3rd less board footage of lumber fewer pieces to handle fewer joist hangers to have to attach and only one half as many screws to attach the roof steel.
Snap a chalk line horizontally across the roof two feet down from the top.
How to install metal roof purlins.
Edit answer for another 41 minute 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.
The typical spacing standards for residential and commercial buildings are about 1 to 2 foot.
Here are two easy formulas for determining the amount of metal roofing screws.
If the space between posts is greater than 8 feet then brace is needed to avoid buckling.
For the lighter material such as lightweight aluminum the common spacing length is 4 inches of clear gap.
Purlin spacing for metal roofing.
Measure the section of the roof from the fascia to the peak and divide this by two which is the two foot spacing of the wood nailers.
Purlin spacing is dependent on profile of the metal and gauge plus snow and wind load plus what the rafters are designed to carry.
Take your square footage and multiply it by 80.
Without a set of blueprints with a pe s seal you have no option but to follow the inspectors gig.
