Max Span
14'-6"
Joist Size
2x10
Joists Needed
12
Total Load
50 psf
14'-6"
2x10
12
50 psf
| Size | Max Span | OK? |
|---|---|---|
| 2x6 | 9'-0" | |
| 2x8 | 11'-10" | |
| 2x10 | 14'-6" | |
| 2x12 | 17'-0" |
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Inputs
Result
SPF #2 2×10 at 16" OC with 40 psf live load has a base span of 174". Grade factor = 1.0, spacing factor = 1.0, load factor = 1.0. Max span = 174" = 14'6". Room width of 14' is within span, so 2×10 works.
Inputs
Result
Douglas Fir #2 2×8 at 16" OC: base span = 157". With 30 psf load factor = 1.10, span = 157 × 1.10 = 173" = 14'5". Room width of 12' is well within span, so 2×8 is sufficient.
A 2×10 SPF #2 joist at 16" OC with 40 psf live load can span up to 14'6". Douglas Fir #2 spans 16'5" and Southern Pine #2 spans 17'4" under the same conditions.
| Species (#2 grade) | 12" OC | 16" OC | 24" OC |
|---|---|---|---|
| SPF 2×10 | 16'0" | 14'6" | 12'8" |
| Douglas Fir 2×10 | 18'0" | 16'5" | 14'3" |
| Southern Pine 2×10 | 19'1" | 17'4" | 15'1" |
For a 16-foot span at 16" OC with 40 psf live load, you need at least a 2×10 in Douglas Fir #2 (16'5" max) or 2×12 in SPF #2 (17'0" max). Southern Pine #2 2×10 also works at 17'4".
| Joist Size | SPF #2 (16" OC) | Douglas Fir #2 (16" OC) | Southern Pine #2 (16" OC) |
|---|---|---|---|
| 2×8 | 11'6" | 12'6" | 13'1" |
| 2×10 | 14'6" | 16'5" | 17'4" |
| 2×12 | 17'0" | 19'1" | 20'3" |
Yes. Closer spacing increases span capacity. At 12" OC, joists can span about 10% more than 16" OC. At 24" OC, span decreases by about 13%. Always check local codes for spacing requirements.
Live load is weight from people, furniture, and movable items (typically 30-50 psf). Dead load is the permanent weight of the structure itself (joists, subfloor, flooring), typically 10-15 psf.
| Space | Live Load (psf) | Dead Load (psf) | Total (psf) |
|---|---|---|---|
| Bedroom | 30 | 10 | 40 |
| Living room | 40 | 10 | 50 |
| Deck / Balcony | 40–60 | 10–15 | 50–75 |
| Storage / Attic | 20–40 | 5–10 | 25–50 |
Deck joists follow different tables due to weather exposure. IRC deck joist spans are typically 10-15% shorter than interior floor joists. Check IRC Section R507 for deck-specific spans.
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Last Updated: Mar 26, 2026
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