It's recommended to use a joist span calculator or to refer to a joist sizing and span table. If the deck will have a diagonal layout, then reduce the spacing to account for the additional distance the boards must cross between joists.Ĭalculating the deck joist span is significantly more difficult and requires the use of several different formulas. Typically, going with 12-inch or 16-inch joist spacing is a safe bet for the project, but if you want to ensure the spacing is adequate for the project, use the following formula:ĭeck Length ÷ (Number of Joists - 1) = Joist Spacingįor example, a deck that measures 20 feet or 240 inches in length with 16 joists should have 16-inch joist spacing. Joists are generally spaced either 12 inches or 16 inches on center, though some builds may opt for eight inches or 24 inches on center. Once you know the material, joist size, and you have a plan with the intended size and shape of the deck, you can calculate the desired deck joist span and spacing.
Redwood, Western Cedars, Ponderosa Pine, Red Pine They are available in both structural and non-structural sections, with this guide providing span tables for common loading scenarios using the structural section sizes. Maximum Joist Span with 16 Inch Joist Spacingĭouglas Fir-Larch, Hem-Fir, Spruce-Pine-Fir Meypine and Rite Pine are H3 preservative treated pre-primed timbers manufactured from sustainably grown plantation softwoods. Maximum Joist Span with 12 Inch Joist Spacing The Spruce Home Improvement Review Board.
