The larger the deck the larger the joists.
Deck floor joist spacing.
Ready to start calculating how much lumber you ll need for your joists.
Please note that when deck joists are cantilevered they should not extend further than one fourth of the actual adjacent joist span according to irc 2015 r507 5.
A 2x8 up to 12 feet.
Southern pine deck joist maximum spans no cantilever with cantilever joists may cantilever up to of the actual adjacent span.
Most composite and pvc decking brands like trex and azek recommend a minimum joist spacing of 16 inches oc.
Deck joist spacing should never exceed 16 on center with the exception of max deck boards which allow for maximum 24 on center.
Deck joist spacing for composite decking remains largely the same as if working with treated lumber.
But you ll notice when you look at the portion of the span table for joists with cantilevers that the joist span for decks with a cantilever is often less than the span for the same sized joist without cantilevers.
On center for standard straight composite decking installation.
Spanning 16 6 between supports may cantilever up to an additional 4 1 for a total maximum length of 20 7.
2x10 to 15 feet and 2x12 to 18 feet.
Section r507 5 notes that deck joists can cantilever up to 1 4 of the joist span.
As a rule the larger the deck the larger the joists.
Two by twelve douglas fir joists spaced 12 inches apart on center for example can span 20 feet 7 inches but the same joists spaced 24 inches part can only span 14 feet 7 inches.
If adding additional framing be sure to keep all boards level and in plane across the tops.
For example a 2 x 12 joist placed 16 oc.
In this instance the maximum span between deck post centres is 2 07m c16 or 2 24m c24.
The maximum joist spans below are based on a ground snow and live load of 40 pounds per square foot and a dead load of 10 pounds per square foot.
We recommend beams are constructed from two 44 x 145mm q deck deck joists and are placed at maximum centres of 1 8m.
Some brands like weardeck let you get away with more reinforced with a layer of fiberglass on both the top and bottom weardeck boards easily allow for spans of 24 inches oc.
To learn more about deck joist sizing spacing and allowable span reference this chart.
For example joists spaced 16 inches from the center of the joist next to it can span 1 5 times in feet the depth of their inches.
For a more rigid feel 12 or less may be preferred.
Maximum 2x6 deck joist span.
