Metal Roof Joist Spacing

Wider panels allow for greater spacing between rafters.

Metal roof joist spacing.

A metal roof must also allow for some overlap on each side of the panels which will reduce the effective width of the panel. Twenty four inches is a common spacing of furring strips for a metal roof. For example in the rafter span table below the highlighted cell in the 40 live load table indicates that 2 x 8 southern yellow pine joists that have a grade of 2 that are spaced 24 apart can have a maximum span of 10 feet 3 inches 10 3 if designing for a live load of 40 lbs ft 2. The tables below give maximum spans for rafters and beams.

In areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot. The same concept holds true for roof trusses. If the roof is not completely square you can decrease the space between joists but never increase the space. Common spacing for trusses on this type of building is often between 2 and 4 feet but trusses built with advanced designs may allow spacing as great as 8 or 12 feet.

In other words you would space a roof joist 15 inches apart from another roof joist but never 17 inches apart. Rafter spacing is based on the width of the metal roofing panels. A roof joist is always spaced no more than 16 inches apart from another roof joist. Typically pole barn style buildings in my area have bays distance between trusses of 5 feet to 12 depending on pitch insulation and height.

Steel roof panel systems west conshohocken pa. The substructure to which the metal panels are fastened must be properly spaced and sufficiently thick to provide a roof or wall system able to meet required design loads. Place corner pieces where panels will meet bends at the edge of the roofing. Use 1 1 4 inch nails to cover the outline of the roof with strips of metal eave flashing also called edging.

Astm e1646 95 2011 standard test method for water penetration of. If purlins are laying flat on top of the truss 5 or 6 feet is the max on 2x4 s edge up can go to 12 feet or more. If there are gutters installed on the eaves the eave flashing should be installed to overhang the lip of the gutter by about 1 2 inch. Truss spacing for metal roof.

So the space between rafters can be greater without reducing the maximum span. The figures are based on quality materials. A 2 nominal lumber thickness provides the maximum pullout values for both screws and nails when the fasteners penetrate a minimum of 1 into the wood. For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.