A common arrangement is a rafter and purlin system which combines purlins and rafters.
Roof framing plan roofing c purlins.
Dead load will be the actual weight of the roof steel and the roof purlins.
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.
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.
The purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to.
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.
They give added support to the roof and also provide a nailing surface for the end panels and drip edge.
We do recommend it however.
The shape of cee purlins does not allow end lapping they are butted together.
Purlins are installed horizontally under metal roofs.
In structural steel or aluminum construction purlins usually w shapes or channels transfer roof loads to the major structural elements supporting the roof.
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.
Welded together they can be used as columns braces and ties.
Cee purlins are secondary steel framing members most commonly used as roof purlins wall girts and header jamb and sill for windows and doors on metal buildings.
A traditional purlin strictly by definition is a horizontal structural member in a roof.
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.
Besides providing support for the roof rafters and purlins add to the interior beauty so you often see log purlins and rafters that match the wall logs.
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.
In the past the majority of roof structures were of wooden construction but over the past 15 to 20 years there has been a vast shift away from wood to metal mainly steel roof construction.
The roof support system is a ridgepole and either rafters which run perpendicular from the top of the walls to the ridge or purlins which run parallel to the ridge.
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.
Purlins are 2 by 4 feet and are installed much like metal roofing.
They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.
The type and spacing of purlins is a design consideration which depends upon the incident roof loads as well as the limiting lengths of sheeting to be used.
In large buildings where heavy trusses are used the purlins are continuous members that rest.
Engineered purlin metal mart offers a complete line of engineered purlin material.
