Horizontal Roof Rafters - Maximum Spans

Douglas Fir in horizontal roof rafters and maximum spans.

Max. Live Load 20 lbs/ft²(956 N/m²)

Maximum Span (ft - in)
Nominal Size (inches)	Rafter Spacing, Center to Center, OC (inches)	Lumber Grade
Nominal Size (inches)	Rafter Spacing, Center to Center, OC (inches)	Selected Structural	No. 1	No. 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)

Maximum Span (ft - in)
Nominal Size (inches)	Joist Spacing Center to Center, OC (inches)	Lumber Grade
Nominal Size (inches)	Joist Spacing Center to Center, OC (inches)	Selected Structural	No. 1	No. 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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