How far can a 2×10 Southern Pine deck joist span at 24″ on center?
| Maximum joist span11.42 ft | 11′ 5″ |
|---|---|
| Maximum cantileverone quarter of the actual span, IRC R507.5.1 | 2′ 10″ |
| Joists across that spanfor a deck as wide as the span is long, at 24″ o.c. | 6joists |
| Species groupthe strongest of the common deck species, and the usual choice in the south-east | Southern Pine |
| — Same size, other spacings — | |
| 2x10 at 12″ o.c. | 16′ 2″ |
| 2x10 at 16″ o.c. | 14′ 0″ |
| 2x10 at 24″ o.c.the combination on this page | 11′ 5″ |
| — Other sizes at 24″ o.c. — | |
| 2x6 at 24″ o.c. | 7′ 7″ |
| 2x8 at 24″ o.c. | 9′ 8″ |
| 2x10 at 24″ o.c. | 11′ 5″ |
| 2x12 at 24″ o.c. | 13′ 6″ |
- Joist size
- 2×10
- Species
- Southern Pine
- Spacing
- 24 in o.c.
The answer
11′ 5″ — a 2×10 Southern Pine joist at 24″ on center, from IRC Table R507.5.
The four assumptions, and all four have to hold
40 psf live load plus 10 psf dead. No. 2 grade lumber. Wet service conditions. No cantilever.
Change any one and the number changes. A hot tub, a heavy planter, a roof over the deck or a snow-load jurisdiction all put you outside this table entirely, and outside it you need an engineer rather than a web page.
What spacing actually buys
The same 2×10 spans 11′ 5″ at 24″ o.c. and 16′ 2″ at 12″ — twice the joists for a gain of a few feet.
Going up a size is usually the cheaper route to more span. Compare the rows below before you decide to halve the spacing.
Species is worth a foot
The same 2×10 at 24″ spans 11′ 5″ in Southern Pine and 10′ 7″ in redwood or cedar. Buying whatever the yard has in stock can quietly cost you a foot of span, and nobody mentions it at the register.
Cantilever
Up to a quarter of the actual span, not the maximum — so 2′ 10″ only if your joists really run 11′ 5″. Joists spanning 10 ft cantilever 2½ ft, whatever this table says.
The inspector has the last word
Local codes amend the IRC. High-snow jurisdictions use higher live loads. Pull the permit before you buy lumber, not after: a deck built to the wrong table comes apart, and it comes apart with people standing on it.
Notes
- **Four assumptions, and all four have to hold.** IRC Table R507.5 is written for 40 psf live load plus 10 psf dead, No. 2 grade lumber, wet service conditions, and no cantilever. Change any one and the number changes. A hot tub, a heavy planter wall or a roof over the deck all put you outside the table entirely.
- Spacing buys more than you would guess. The same 2x10 goes from 11′ 5″ at 24″ o.c. to 16′ 2″ at 12″ — a gain of 4′ 9″ for twice the joists. Going up a size is usually cheaper: a 2x12 at 24″ reaches 13′ 6″.
- Species matters more than most people expect. The same 2x10 at 24″ spans 11′ 5″ in Southern Pine and 10′ 7″ in redwood or cedar. Buying "whatever the yard has" can quietly cost you a foot of span.
- Cantilever is capped at a quarter of the **actual** span, not the maximum. If your joists span 10 ft, the overhang can be 2½ ft even though this row says 2′ 10″.
- **The inspector has the last word.** Local codes amend the IRC, and high-snow jurisdictions use higher live loads. Pull the permit before you buy the lumber, not after — a deck built to the wrong table comes apart, and it usually comes apart with people on it.
Nearby sizes
- How far can a 2×8 Southern Pine deck joist span at 24″ on center?
- How far can a 2×12 Southern Pine deck joist span at 24″ on center?
- How far can a 2×6 Southern Pine deck joist span at 24″ on center?
- How far can a 2×10 Douglas Fir-Larch deck joist span at 24″ on center?
- How far can a 2×10 redwood or cedar deck joist span at 24″ on center?
- How far can a 2×10 Southern Pine deck joist span at 16″ on center?
- How far can a 2×10 Southern Pine deck joist span at 12″ on center?
Read more
- Deck Joist Cantilever: One Quarter of the Actual Span, Not the MaximumThis is the most misread line in the deck code, and it is misread in the direction that puts the beam too far in.
- Ledger Attachment: The Detail That Causes Nearly Every Deck CollapseSpan tables get the attention. Ledger failure is what actually drops decks, and it is almost always one of four specific mistakes.
- Deck Joist Span Tables: The Four Assumptions That Have to HoldThe span table is not a rule about lumber. It is a rule about lumber carrying 40 psf, dry, at No. 2 grade, with no cantilever, and any of those can be false on your deck.
- Composite or Pressure-Treated? The 20-Year Arithmetic, Including the Part Nobody CountsComposite wins the twenty-year total only if you would actually have refinished the wood. Most people do not, which is why most wood decks look their age.