In large buildings where heavy trusses are used the purlins are continuous members that rest.
Roofing roof framing plan c purlins.
Under purlins were typically propped off internal walls.
Engineered purlin metal mart offers a complete line of engineered purlin material.
When repairing or replacing a roof it pays to be familiar with these terms.
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.
Includes illustrations that show roofs have hip rafters ridge boards jack rafters and more.
We do recommend it however.
Purlins purlins are used in roof construction to support corrugated sheet metal if it is used or to support the sheathing of roofs framed with trusses.
In addition our c section purlins can also be used for door framing roof trimming window trimming parapet rails and side rails also see z purlins page.
In traditional timber truss construction purlins rest on the principal rafters of the truss.
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 facia frame may also supports the soffit.
They give added support to the roof and also provide a nailing surface for the end panels and drip edge.
This frame supports and is hidden by a metal facia board.
Metal c purlins are light in weight and perfect for simple span construction.
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.
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.
In small roofs purlins are inserted between the rafters and nailed through the rafters.
The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to.
The steel purlins are in turn supported by rafters or walls.
C section purlins or cee section purlins are designed to form the walls and floor joists of a building shell structure making them also ideal for supporting beams needed for mezzanine flooring.
Roof framing involves a lexicon all its own.
Do all roofing projects require purlins.
Here is a closer look at common roofing terms.
The purlins support the long span steel roofing but before the roof itself is put on a metal facia frame is installed around the perimeter of the roof.
Metal roof purlins are installed horizontally under metal roofs.
For example an 8 x 4 under purlin would support the center of a row of 6 x 2 rafters that in turn would support 3 x 2 roof purlins to which the roof cladding was fixed.
They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.
Purlins are 2 by 4 feet and are installed much like metal roofing.
