Screw line spacing for metal roofing over metal purlins.
Steel roof purlin spacing.
Engineered purlin metal mart offers a complete line of engineered purlin material.
The width of metal panels will determine the rafter spacing.
The purlin are ultimately used to fasten the roof steel providing a diaphragm effect along with the siding when properly engineered and installed.
Metal roof purlins are installed horizontally under metal roofs.
The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to.
Purlins are 2 by 4 feet and are installed much like metal roofing.
Spacing is typically 24 on center in low snow loads and is reduced based upon truss span and snow load.
This will depend upon the type of panel that is used and the thickness of the steel.
Do all roofing projects require purlins.
The wider the roofing panels the greater spacing distance you should put.
For sake of discussion we will assume a minimal roof snow load of 20 psf pounds per square foot and a 4 12 roof slope.
Once the purlin spacing is determined then the metal roofing panels are typically attached to every line of purlins.
The purpose of purlins.
We do recommend it however.
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 metal roof purlins spacing must be done correctly within narrow tolerances.
They give added support to the roof and also provide a nailing surface for the end panels and drip edge.
First the purlins support the roof.
Secondly purlins tie the rafters together stabilizing and strengthening the structure s rigid framing.
There is a chance of damaging roofing sheets if you are failed to do so.
Metal building roof purlins provide three structural functions.
An engineer will use a load chart in order to determine the spacing between metal purlins.
They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.
Available in cee or zee shape red oxide primed or galvanized 16 14 or 12 gauge sizes from 4 up to 12 flange widths of 1 1 2 up to 4 cut to your specified lengths hole punching available load tables available for all material.
Also known as sheeting rails purlins create the roofing members of the secondary framing of a steel building.
However the screw placement diagrams commonly are based on the on center spacing center to center of the purlin rather than the gap between purlins to determine the length and spacing of the screws needed to prevent wind blowoff for various design wind speeds so pay close attention to that difference.
The building was built 24 on center.
