Maximum Floor Joist Span
No. 1 and No. 2 Grade of Douglas fir and maximum span floor joists - imperial units
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Maximum floor joist span for No. 1 and No. 2 Grade of Douglas fir are indicated below. Max. dead load (weight of structure and fixed loads) 10 lbs/ft2. Live load is weight of furniture, wind, snow and more.
- 1 psf (lbf/ft2) = 47.88 N/m2
- 1 ft = 0.3048 m
- 1 in = 25.4 mm
Max. Live Load 30 lbs/ft2 (1436 N/m2)
| Maximum Span (ft - in) | ||||
|---|---|---|---|---|
| Nominal Size (inches) |
Joist Spacing Center to Center (inches) |
Lumber Grade | ||
| Selected Structural | No. 1 | No. 2 | ||
| 2 x 6 | 12 | 12' - 6'" | 12' - 0" | 11' - 10" |
| 16 | 11' - 4" | 10' - 11" | 10' - 9" | |
| 24 | 9' - 11" | 9' - 7" | 9' - 1" | |
| 2 x 8 | 12 | 16' - 6" | 15' - 10" | 15' - 7" |
| 16 | 15' - 0" | 14' - 5" | 14' - 1" | |
| 24 | 13' - 1" | 12' - 4" | 11' - 6" | |
| 2 x 10 | 12 | 21' - 0" | 20' - 3" | 19' - 10" |
| 16 | 19' - 1" | 18' - 5" | 17' - 2" | |
| 24 | 16' - 8" | 15' - 0" | 14' - 1" | |
| 2 x 12 | 12 | 25' - 7" | 24' - 8" | 23' - 0" |
| 16 | 23' - 3" | 21' - 4" | 19' - 11" | |
| 24 | 20' - 3" | 17' - 5" | 16' - 3" | |
Max. Live Load 60 lbs/ft2 (2873 N/m2)
| Maximum Span (ft - in) | ||||
|---|---|---|---|---|
| Nominal Size (inches) |
Joist Spacing Center to Center (inches) |
Lumber Grade | ||
| Selected Structural | No. 1 | No. 2 | ||
| 2 x 8 | 12 | 13' - 1" | 12' - 7" | 12' - 4" |
| 16 | 11' - 11" | 11' - 5" | 10' - 8" | |
| 24 | 10' - 5" | 9' - 4" | 8' - 8" | |
| 2 x 10 | 12 | 16' - 8" | 16' - 1" | 15' - 0" |
| 16 | 15' - 2" | 13' - 11" | 13' - 0" | |
| 24 | 13' - 3" | 11' - 4" | 10' - 7" | |
| 2 x 12 | 12 | 20' - 3" | 18' - 7" | 17' - 5" |
| 16 | 18' - 5" | 16' - 1" | 15' - 1" | |
| 24 | 15' - 10" | 13' - 2" | 12' - 4" | |
| 2 x 14 | 12 | 23' - 11" | 20' - 10" | 19' - 5" |
| 16 | 21' - 8" | 18' - 0" | 16' - 10" | |
| 24 | 17' - 9" | 14' - 8" | 13' - 9" | |
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