deck joist span calculator · 2,400/mo searches
Deck Joist Span Calculator (IRC R507.6)
How far can a deck joist span? It depends on the joist size, the on-center spacing and the lumber species. Enter your deck below and the calculator reads the maximum span straight from IRC Table R507.6, the same table your plans examiner uses.
Member sizes read from the IRC R507.6 (joists) and R507.5 (beams) tables for No. 2 Southern Pineat 40 psf live + 10 psf dead. Footings from tributary load ÷ soil bearing (R507.3); ledger fasteners per R507.9. Confirm with your local building department.
| Decking: Pressure-treated pine192 sq ft · ~28 × 16′ boards · Shop materials ↗ | $575–$1,730 |
| Substructure (joists, beam, posts, hardware)192 sq ft framing · Shop materials ↗ | $1,150–$2,495 |
| Footings (concrete piers)4 posts · Shop materials ↗ | $140–$360 |
| Railing / guard40 lin ft · Shop materials ↗ | $600–$2,400 |
| Stairs4 treads · Shop materials ↗ | $120–$380 |
| Permit + fasteners + miscallowance | $75–$500 |
| Total estimate | $2,660–$7,865 |
Low is a DIY material budget; high is contractor-installed with labor. Regional prices vary, so treat this as a planning range, not a quote.
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Turn this deck into a permit-ready PDF: title block, elevation, framing & footing schedules, code citations.
Full deck joist span table (IRC R507.6)
| Joist | 12" o.c. | 16" o.c. | 24" o.c. |
|---|---|---|---|
| 2x6 | 9'11" | 9' | 7'7" |
| 2x8 | 13'1" | 11'10" | 9'8" |
| 2x10 | 16'2" | 14' | 11'5" |
| 2x12 | 18' | 16'6" | 13'6" |
| Joist | 12" o.c. | 16" o.c. | 24" o.c. |
|---|---|---|---|
| 2x6 | 9'6" | 8'4" | 6'10" |
| 2x8 | 12'6" | 11'1" | 9'1" |
| 2x10 | 15'8" | 13'7" | 11'1" |
| 2x12 | 18' | 15'9" | 12'10" |
| Joist | 12" o.c. | 16" o.c. | 24" o.c. |
|---|---|---|---|
| 2x6 | 8'10" | 8' | 6'10" |
| 2x8 | 11'8" | 10'7" | 8'8" |
| 2x10 | 14'11" | 13' | 10'7" |
| 2x12 | 17'5" | 15'1" | 12'4" |
Deck Joist Span: what to know
- •Spans are clear, face-of-support to face-of-support, for No. 2 grade lumber at 40 psf live + 10 psf dead load.
- •Tighter spacing spans further: a 2x8 Southern Pine goes 13'1" at 12" o.c. but only 9'8" at 24" o.c.
- •Joist cantilevers past the beam are limited to 1/4 of the back-span (IRC R507.6.1).
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