What Size Purlins For Metal Roof

Bending stresses f b.

What size purlins for metal roof.

Purlins are 2 by 4 feet and are installed much like metal roofing. They give added support to the roof and also provide a nailing surface for the end panels and drip edge. Purlins are installed horizontally under metal roofs. 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.

Temperature factor c t 1 nds 2 3 3. If you want to know how to support roof purlins they are usually supported by 2 4 or 2 6 struts or posts. For 2x4s purlins the posts are spaced in 4 feet distance. Step 1 run a tape measure from end to end along the rafters of the roof to determine how many purlins will be needed for installation.

The typical spacing standards for residential and commercial buildings are about 1 to 2 foot. Load duration factor c d 1 15 nds 2 3 2 c m. Boards measuring 1 inches by 4 inches or 2 inches by 4 inches are commonly used for purlins though never use treated lumber because it will corrode the steel roof and fasteners. The standard of purlin length will vary anywhere between 100 to 300 mm while the thickness will vary anywhere between 1 to 3 mm.

For heavier material such as gage steel the metal roof purlins spacing length could go up to 4 feet. Allowable bending pressure f b f b c d c m c t c l c f c fu c i c r c d. For the lighter material such as lightweight aluminum the common spacing length is 4 inches of clear gap. 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.

Cee purlin lengths are cut to length from 6 45 in 1 8 increments though 20 and 25 are the most commonly chosen lengths. 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 purpose of the purlins is to provide a solid foundation for the metal roofing panels and trim to be screwed to.

Total purlin dead load 1 638 psf. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.