![]() 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. 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 following updated APA-The Engineered Wood Association standards were also approved for reference: ANSI A190. The following span table uses a moderate snow load of 50 Psf, but yours could be more or less. BASE VALUES for dimension lumber computed. Consult your local building code authority to determine the snow load in your area. Western Wood Products Association for Floor and Ceiling Joists and Roof Rafters. With these inputs, the calculator analyzes forces and structural capacity to output an appropriately sized rafter. The steps are in accordance with Chapter 8 of IRC 2018 and Clauses 23.4, 28.1.1, 28.2.1.1 and 28.3.1 of IS 875-1987.All relevant formulas used are shown. International Residential Code 2015 (IRC 2015) Code Compare. Note: Snow load factors can be specific to the regional location of a structure. Therefore, 2×6 size Douglas Fir-Larch rafter at 2 ft spacing is adequate. Rafter Span Tables Rafters with ceiling not attached to rafters, live load = 20 Psf, dead load = 20 Psf, deflection limit L/180 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. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |