![]() Table R502.3.1(1) shall be used to determine the maximum allowable span of floor joists that support sleeping areas and attics that are accessed by means of a fixed stairway in accordance with Section R311.7 provided that the design live load does not exceed 30 pounds per square foot (1. To calculate the maximum spans of species not shown above, use the Span Calculator or the Span Tables for Joists and Rafters on the American Wood Council website. R502.3.1 Sleeping areas and attic joists. ![]() To calculate maximum rafter spans using different design criteria (load, snow load, spacing, grade, etc.) for these common lumber species, see the International Residential Code (IRC). The span values (displayed above) are from the American Softwood Lumber standard sizes. Rafters with ceiling not attached to rafters, ground snow load = 50 Psf, dead load = 20 Psf, deflection limit L/180 The greater the space between rafters, the shorter the distance they can span. No other company in the industry, regardless of size, can offer this comprehensive range of Design/Build Solutions to the design and contracting communities. The following span table uses a moderate snow load of 50 Psf, but yours could be more or less. Rafter joist spacing is only one aspect of roof design and building that affects the span, along with load variables, wood species, and grade. The Super Stud Affiliation of Companies manufacture and supply all of the necessary products and components to construct a complete, dried-in structural shell. Consult your local building code authority to determine the snow load in your area. Note: Snow load factors can be specific to the regional location of a structure. Other span tables are based on the guidance given in BS 5268-7.1 which is a uniformly distributed load of 1. Rafter Span Tables - Use these tables to determine maximum rafter length. What next Leave rafter span tables and return Home. Rafter Span Tables Rafters with ceiling not attached to rafters, live load = 20 Psf, dead load = 20 Psf, deflection limit L/180 The floor joist span tables are based on the loadings given in the amended version of BS 6399-1 which is an imposed load of either a uniformly distributed load of 1.5 kN/m² or a concentrated load of 1.4 kN. hese span tables for joists and rafters are calculated T on the basis of a series of modulus of elasticity (E) and bending design values (F b Additionally, compression perpendicular to grain design values (F c ) are included as a consideration for selection of joists and rafters. Ceiling Joist Span Tables - How to determine the size and maximum length of ceiling joists. The braces need to be supported by a bearing wall, shown in the diagram above.Įxample: In the rafter span table below, the highlighted cell (13-0) indicates that a 2" x 8" Douglas Fir rafter, with a grade of #2, spaced 24" apart, can have a maximum span of 13 feet - 0 inches (13-0) if designed for a live load of 20 Psf, and dead load of 20 Psf. Note also that you can break up the span of a rafter by adding a purlin and bracing to the underside. When calculating the maximum span of a rafter, use the horizontal distance between two vertical supports. Tables listing Maximum Spans for Southern Pine joists and rafters are detailed below.
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