Purlin spacing for metal roofing.
Purlin spacing for corrugated metal 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.
We do recommend it however.
Without a set of blueprints with a pe s seal you have no option but to follow the inspectors gig.
The screws are spaced out so that every third corrugation has a screw.
Corrugated sheet roofing material is widely available and easy to use.
Fyi we run purlins on 3 5 feet on center depending on size of purlin.
When framing the roof the spacing for roof trusses should not exceed 24 inches 61 cm and purlins should not exceed 36 inches 91 cm apart.
When using purlins fabral recommends a maximum spacing of 24 on center note that 5v requires solid decking.
The overlaps ends and sides depends upon the sloop of the roof see below.
The typical spacing standards for residential and commercial buildings are about 1 to 2 foot.
Be sure the larger edge is laid so that the small edge of the next panel will overlap it.
Purlin spacing should suit the end laps required for the size of sheet to be used.
Purlins provide horizontal support for the sheets and form part of the framework for the building.
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 sometimes corrugated sheets are 39 wide instead of 37 wide.
Pullout values decrease if the fasteners protrude completely through the purlins.
Corrugations should run in a straight line between the highest and lowest points and at a right angle to the purlins the intermediate supports.
Align the first metal roofing panel so that it overlaps the edging by 1 2 to 3 4 of an inch and is square to the roof line.
For the lighter material such as lightweight aluminum the common spacing length is 4 inches of clear gap.
There will be four screws per screw line placed in the high of the corrugated panel.
Install the roofing screws vertically along each rib in the panel.
Minimum recommended purlin size is 4 x 2 50mm x 100mm in timber or z140mm x 1 6mm in steel.
All purlin joints must be supported by a rafter.
These panels can cost more to install that a traditional roof but in the long run are often a better value.
Corrugated metal panels often called tin because in the past such panels were sometimes made of tin are typically steel or aluminum sheets that are used as a roofing material.
The diagram above is a typical 37 wide panel and the spacing works out perfectly.
Do all roofing projects require purlins.
Kiln dried softwood is recommended for purlins or decking pine fir hemlock and spruce.
