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.
1x4 perlins for metal roof.
We do recommend it however.
Engineered purlin metal mart offers a complete line of engineered purlin material.
Most you see on homes and many commercial building is non structural metal roofing and needs to be on solid sheathing.
The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to.
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 roofing is manufactured in panels that.
There are two ways to do this put in firring nailing though nails are not used any more for this strips or purlins in steel frame construction on the roof to support it or place the metal roofing directly on a flat surface like foam insulation board or the roof sheathing with roof water barrier in the correct position in the layer.
On metal frame building and the like you will likely see structural metal roofing installed on purlins that is what those 1x4 are purlins and those metal roofing panels are rated for that type of installation.
Tin roofing also known as metal roofing is considered more durable than composition or wood shingles.
Do all roofing projects require purlins.