Deck Joist Span Chart & Calculator
Look up maximum deck joist span and allowable overhang from AWC DCA 6-15 Table 2. Built for US DIY builders and small contractors who need a fast, code-referenced answer.
Deck joist span calculator
Pick species group, joist size, and spacing. Results come straight from AWC DCA 6-15 Table 2.
Use the lesser of the table overhang and one-fourth of the actual joist span (L/4). Ledger and guard-post members must be at least 2x8 nominal per DCA 6.
Deck joist span chart / table (AWC DCA 6)
Full Table 2 values: three species groups × four sizes × three spacings, with span and overhang.
Source: AWC DCA 6-15 PDF, Table 2.
Deck joist span guide
What is deck joist span?
Deck joist span is the clear distance from the face of one support to the face of the next—ledger to beam, or beam to beam on a non-ledger deck. It does not include the overhang past the beam. If your joists hang past the beam, that cantilever is checked separately against the overhang column in Table 2 and against L/4.
How to use this chart / calculator
1) Choose the species group that matches your lumber stamp. 2) Pick the nominal joist size. 3) Pick on-center spacing. The calculator returns the maximum allowable span and the table overhang. Compare your planned clear span to that number; if you need more length, tighten spacing, step up a size, or add a beam.
Assumptions behind the numbers
AWC DCA 6 Table 2 assumes 40 psf live load, 10 psf dead load, No. 2 grade, wet service, and L/360 deflection for the main span. Overhangs are limited by a 220 lb point load at L/180 cantilever deflection, and must also stay within L/4 of the actual main span. Read the full write-up on our assumptions page.
Joist size guide (2x6–2x12)
Smaller joists cost less but limit how far you can go without an intermediate beam. DCA 6 also requires a minimum 2x8 for the ledger and for any joist or rim that receives a guard post—even if a 2x6 would span for strength.
Spacing: 12, 16, and 24 inches on center
Closer spacing raises the allowable span for the same size. Many composite decking products also require 12″ or 16″ o.c. regardless of the joist table—always check the decking manufacturer. See the 16 inch on center slice for a common layout.
Overhang / cantilever rules
The allowable overhang LO is the smaller of the Table 2 value and one-fourth of the actual joist span. A long table overhang does not help if your back span is short. Details on the joist overhang page.
Species by US region (brief)
Southern Pine is common in the Southeast. Douglas Fir-Larch, Hem-Fir, and SPF show up widely inland and in the West/North. Redwood and Western Cedars are popular on the West Coast for appearance and natural durability; Ponderosa and Red Pine appear in northern species groupings. Use the stamp on the board, not a guess from geography alone. Southern Pine values: southern pine deck joist span.
Local code & engineer disclaimer
Your city or county may amend the IRC, require snow loads above 40 psf, or ask for sealed drawings. Treat this site as a planning aid. For hot tubs, roofs, multi-level decks, or unusual geometry, hire a licensed engineer.
FAQ
How far can a 2x8 deck joist span?
At 16″ o.c., Southern Pine reaches 11'-10"; DF-L / Hem-Fir / SPF reaches 11'-1"; Redwood / Western Cedars reach 10'-7" per DCA 6 Table 2. See 2x8 deck joist span.
How far can a 2x10 deck joist span?
At 16″ o.c.: 14'-0" (Southern Pine), 13'-7" (DF-L/HF/SPF), 13'-0" (Redwood group). Full grid on 2x10 deck joist span.
How far can a 2x12 deck joist span?
At 16″ o.c.: 16'-6" Southern Pine, 15'-9" DF-L/HF/SPF, 15'-1" Redwood group. At 12″ o.c. Southern Pine and DF-L hit the guide’s 18'-0" joist-length limit.
How far can a 2x6 deck joist span?
At 16″ o.c.: 9'-0" Southern Pine, 8'-4" DF-L/HF/SPF, 8'-0" Redwood group. Remember ledger and guard-post members still need 2x8 minimum.
What does 16 inch on center mean for deck joists?
Joists are spaced so their centers are 16 inches apart. It is the most common residential spacing and balances lumber cost with span capacity. See joist spacing 16.
Is joist span the same as decking span?
No. Joist span is how far the joist can run between beams; decking span is how far the deck boards can run between joists. See decking joist span.
Where do these numbers come from?
American Wood Council DCA 6-15, Table 2, based on the 2015 IRC. We transcribed the cells into JSON—no invented spans.