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Joist span table for floor joists

Floor joist spans for various sizes and species of wood

Joist span table - Use these tables to determine floor joist spans based on grade of lumber, size of joist, floor joist spacing, and a live load of 30 lbs/ft2 or 40 lbs/ft2.  These tables can also be used to determine deck joist span.

 For example, in the joist span table below, the highlighted cell shows that 2" x 8"  Southern Yellow Pine joists, that have a grade of #2, and are spaced 24" apart can have a maximum span of 10 feet - 3 inches (10-3) if designing for a live load of 40 lbs/ft2.

Nominal Size Spacing (o.c.) Species and Grade of Lumber ( based on 30 lb / ft2. Live Load)
Southern Yellow Pine Southern Yellow Pine Douglas Fir Eastern Spruce
#1 grade (kiln dried) #2 grade #2 grade Structural
2" x 6" 12 12-6 11-3 12-0 11-0
16 11-4 10-10 10-11 10-0
24 9-11 8-8 9-7 8-9
2" x 8" 12 16-6 14-11 15-10 14-6
16 15-0 13-6 14-5 13-2
24 13-1 11-6 12-7 11-6
2" x 10" 12 21-0 19-0 20-3 18-6
16 19-1 17-3 18-5 16-10
24 16-8 14-7 16-1 14-8
2" x 12" 12 25-7 23-1 24-8 22-6
16 23-3 21-0 22-5 20-6
24 20-3 17-9 19-7 17-11

Nominal Size Spacing (o.c.) Species and Grade of Lumber ( based on 40 lb / sq. ft. Live Load)
Southern Yellow Pine Southern Yellow Pine Douglas Fir Eastern Spruce
#1 grade (kiln dried) #2 grade #2 grade Structural
2" x 6" 12 11-4 10-3 10-11 10-1
16 10-4 9-4 9-11 9-2
24 9-0 7-9 8-8 7-11
2" x 8" 12 15-0 13-6 14-5 13-2
16 13-7 12-3 13-1 12-0
24 11-11 10-3 11-3 10-6
2" x 10" 12 19-1 17-3 18-5 16-10
16 17-4 15-8 16-9 15-3
24 15-2 13-1 14-6 13-4
2" x 12" 12 23-3 21-0 22-5 20-6
16 21-1 19-1 20-4 18-7
24 18-5 15-11 17-6 16-3

The above spans are based on American Softwood Lumber standard sizes.

** Note: The data in the floor joist span tables above was obtained from Architectural Drawing and Light Construction by Edward J. Muller.


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