2×6 deck joist spans (2021 IRC)

2×6 deck joist spans by load case, species group, and spacing

Rows are the table's own load cases and species groups; columns are joist spacing, on center. Every value is quoted from 2021 IRC Table R507.6 as printed.

2021 IRC Table R507.6 — 40 psf live load, 50 psf ground snow load, 60 psf ground snow load, 70 psf ground snow load; 10 psf dead load, No. 2 grade, wet service factor included, deflection L/360. Table source

2×6 deck joist cantilever limits

The cantilever columns are keyed to the joist back span — the span behind the support the joist runs past. Find the back span across the top, read down to the species group and load case, and the cell is the longest cantilever Table R507.6 lists for that combination. NP means not permitted by the table. For a 2×6 Southern pine under the 40 psf live load case the table lists 1’0” at a 4-foot back span and 1’5” at an 8-foot back span, and NP from a 10-foot back span on.

Two conditions come with those columns as the table states them: a 220-pound point load at the free end of the cantilever, and deflection at the cantilever held to L/180 rather than the L/360 that applies to the back span.

2021 IRC Table R507.6 — maximum cantilever under the same load cases (40 psf live load, 50 psf ground snow load, 60 psf ground snow load, 70 psf ground snow load), with a 220-pound point load at the free end and deflection at the cantilever held to L/180. Table source

Reading the load case rows

The first block is the 40 psf live load case — the deck itself, with people and furniture on it. The 50 psf ground snow load, 60 psf ground snow load, 70 psf ground snow load blocks are ground snow load cases: the snow load on the ground at your address, which your building department publishes, not the depth of snow sitting on the deck. Pick the row that matches your jurisdiction's ground snow load, and where the ground snow load falls between the table's rows, the next row up is the one the table covers.

Under the 70 psf ground snow load case, a 2×6 Southern pine deck joist at 16-inch centers is listed at 7’6” against 9’0” under the 40 psf live load case — the same stick of lumber, a different row of the same table.

Point loads, cantilevers beyond the table footnotes, unusual snow loads, or anything else outside the table's stated conditions — that's an engineer's question.

Common questions

Other deck joist sizes and the rest of the deck

Deck joists: 2×6 · 2×8 · 2×10 · 2×12

The beam the joists land on is a different table: deck beam spans (2021 IRC Table R507.5(1)). For the same size indoors, see 2×6 floor joist spans.