Deck Joist Span

2x8 Deck Joist Span

2x8 is the workhorse size for many residential decks. It meets DCA 6’s minimum for ledgers and guard-post joists while spanning farther than 2x6.

2x8 span & overhang by species

Notes for 2x8 joists

At 16″ o.c. you get 11'-10" (Southern Pine), 11'-1" (DF-L/HF/SPF), or 10'-7" (Redwood group). Compare with 2x6 and 2x10.

All values assume 40 psf live / 10 psf dead, No. 2, wet service. Confirm overhang with L/4. Full context on the deck joist span home page.

2x6 span2x10 span2x12 spanSouthern PineCalculatorDeck joist span

Planning tips

Measure clear span from the face of the ledger (or beam) to the face of the far beam—do not count the overhang in that measurement. If your layout needs more length than Table 2 allows at your preferred spacing, you can tighten spacing, step up a joist size, or add an intermediate beam. Composite decking may force 12″ or 16″ o.c. even when the joist table would allow 24″.

Guard posts and ledgers still need at least 2x8 nominal members under DCA 6, regardless of how short the joist span is. Wet-service No. 2 values already include the reductions used in Table 2; do not “upgrade” the spans for dry use without an engineer. Snow loads above 40 psf, hot tubs, and roofed decks are outside this table.

Cross-check any number you rely on against the official AWC DCA 6 PDF Table 2, and confirm local amendments with your building department before you order lumber.

Disclaimer

This site is a reference tool. Span and overhang values are transcribed from the American Wood Council DCA 6-15 Table 2 (based on the 2015 IRC). It is not engineering design. Always follow your local building code and a licensed design professional. These tables do not apply to snow loads above 40 psf, hot tubs, roofed decks, or other concentrated loads.