Deck Joist Span Chart — IRC R507.6
Maximum allowable deck joist spans per IRC Table R507.6 — 40 psf live load + 10 psf dead load, #2 grade lumber. Spans are measured as the clear distance between supports.
Local codes may require stricter spans. Always verify with your building department before purchasing lumber. Use the Joist Span Calculator for interactive pass/fail results.
Douglas Fir-Larch #2
| Size | 12″ O.C. | 16″ O.C. | 24″ O.C. |
|---|
| 2×6 | 9′-9″ | 8′-10″ | 7′-8″ |
| 2×8 | 13′-1″ | 11′-10″ | 9′-8″ |
| 2×10 | 16′-3″ | 14′-8″ | 11′-11″ |
| 2×12 | 18′-0″ | 17′-0″ | 13′-10″ |
Southern Yellow Pine #2
| Size | 12″ O.C. | 16″ O.C. | 24″ O.C. |
|---|
| 2×6 | 10′-9″ | 9′-9″ | 8′-1″ |
| 2×8 | 14′-2″ | 12′-10″ | 10′-6″ |
| 2×10 | 17′-1″ | 15′-6″ | 12′-8″ |
| 2×12 | 19′-8″ | 17′-10″ | 14′-7″ |
Hem-Fir #2
| Size | 12″ O.C. | 16″ O.C. | 24″ O.C. |
|---|
| 2×6 | 9′-4″ | 8′-5″ | 6′-10″ |
| 2×8 | 12′-4″ | 11′-2″ | 9′-2″ |
| 2×10 | 15′-3″ | 13′-10″ | 11′-4″ |
| 2×12 | 17′-8″ | 16′-0″ | 13′-1″ |
Quick rules of thumb
- • 16″ O.C. is the standard for most deck framing — check your composite decking manufacturer, some require 12″.
- • Southern Yellow Pine spans noticeably farther than Hem-Fir — worth specifying if available.
- • Add a mid-span beam (or reduce span) before going to a larger joist size — it often costs less.
- • These spans are for deck joists only. Interior floor joists use different load tables.
Related tools & references
