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Maximum Floor Joist Span

No. 1 and No. 2 Grade of Douglas fir and maximum span floor joists - imperial units

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/ft2Live 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

Floor joists - maximum span

Max. Live Load 30 lbs/ft2(1436 N/m2)

Maximum Floor Joist Span, Live Load 30 lbs/ft2(1436 N/m2) (ft - in)
Nominal Size
(inches)
Joist Spacing Center to Center
(inches)
Lumber Grade
Selected StructuralNo. 1No. 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 Floor Joist Span, Live Load 60 lbs/ft2(1436 N/m2) (ft - in)
Nominal Size
(inches)
Joist Spacing Center to Center
(inches)
Lumber Grade
Selected StructuralNo. 1No. 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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