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Horizontal Roof Rafters - Maximum Spans

Douglas Fir in horizontal roof rafters and maximum spans.

Douglas fir maximum horizontal roof rafter span for Lumber Grade Selected Structural and No. 1 and No. 2, are indicated below.

Max. dead load (weight of structure and fixed loads) 15 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 20 lbs/ft2(956 N/m2)

Horizontal Roof Rafters - Maximum Spans - Max. Live Load 20 lbs/ft2(956 N/m2)
Nominal Size
(inches)		Rafter Spacing, Center to Center, OC
(inches)		Maximum Span (ft - in)
Lumber Grade
Selected StructuralNo. 1No. 2
2 x 6 12 16' - 4'' 15' - 9'' 14' - 9''
16 14' - 11'' 13' - 8'' 12' - 9''
24 13' 11' - 2'' 10' - 5''
2 x 8 12 21' - 7'' 19' - 11'' 18' - 8''
16 19' - 7'' 17' - 3'' 16' - 2''
24 17' 14' - 1'' 13' - 2''
2 x 10 12 27' - 6'' 24' - 4'' 22' - 9''
16 25' 21' - 1'' 19' - 9''
24 20' - 9'' 17' - 3'' 16' - 1''
2 x 12 12 33' - 6'' 28' - 3'' 26' - 5''
16 29' - 5'' 24' - 5'' 22' - 10''
24 24' 20' 18' - 8''

Max. Live Load 60 lbs/ft2(2873 N/m2)

Horizontal Roof Rafters - Maximum Spans - Max. Live Load 60 lbs/ft2(2873 N/m2)
Nominal Size
(inches)		Joist Spacing Center to Center, OC
(inches)		Maximum Span (ft - in)
Lumber Grade
Selected StructuralNo. 1No. 2
2 x 8 12 15' - 0'' 13' - 7'' 12' - 3''
16 13' - 7'' 11' - 9'' 11'
24 11' - 7'' 9' - 8'' 9'
2 x 10 12 19' - 1'' 16' - 8'' 15' - 7''
16 17' - 4'' 14' - 05'' 13' - 6''
24 14' - 2'' 11' - 9'' 11'
2 x 12 12 23' - 3'' 19' - 3'' 18'
16 20' - 1'' 16' - 8'' 15' - 7''
24 16' - 5'' 13' - 8'' 12' - 9''
2 x 14 12 25' - 11'' 21' - 7'' 20' - 2''
16 22' - 6'' 18' - 8'' 17' - 5''
24 18' - 4'' 15' - 3'' 14' - 3''

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