![]() ![]() For other grades and species and for other loading conditions, refer to the AWC STJR. For determination of roof rafter sizes, reduction of roof spans shall be permitted where a roof rafter support brace is installed in accordance with Section R804.3.2.2. Live load is weight of furniture, wind, snow and more. Rafter spans shall be measured along the horizontal projection of the rafter. Roof rafter size and thickness shall be determined in accordance with the limits set forth in Table R804.3.2.1(1) based on the horizontal projection of the roof rafter span. dead load (weight of structure and fixed loads) 15 lbs/ft 2. 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. Douglas fir maximum horizontal roof rafter span for Lumber Grade Selected Structural and No. To calculate maximum joist spans using different design criteria (loading, spacing, grade, etc.) for these common lumber species, see the International Residential Code (IRC). RAFTER SPACING (inches) TABLE R802.5. The above spans are from the American Softwood Lumber standard sizes. Uninhabitable attics with limited storage, a live load of 20 Psf, a dead load of 10 Psf, and a deflection limit of L/240 Whenever calculating of maximum scope of a rafter, use of horizontal distances between two vertically supports. TJI 110, 210, 230, 360, 560 Bar Specifiers Orientation (Canada) Rafter Span Diagram. Listed are 46 tables based on common loading conditions for floor joists, ceiling joists and rafters. The second range table is to same as the primary, except that it assumes a ground snow load concerning 50 psf. ** Span is greater than 26 feet in length. Simplified maximum span tables for selected visual and mechanical grades of Southern Pine lumber in sizes 2×4 thru 2×12. Ceiling Joist Span Tables Uninhabitable attics without storage, a live load of 10 Psf, a dead load of 5 Psf, and a deflection limit of L/240 Based on the following design requirements: an uninhabitable attic with limited storage has a live load of 20 Psf, a dead load of 10 Psf, and a deflection limit of L/240 (span in inches divided by 240). Example: The highlighted cell (below) shows that a 2" x 6" Douglas Fir joist, with a grade of #2, spaced 24" apart, can have a maximum span of 10 feet - 8 inches (10-8).
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