Joists

 

MAXIMUM CLEAR JOIST SPANS

Southern Pine #2. 
Residential living areas Live Load = 40 psf.
Dead Load = 10 psf.

 

 

 

 Joist Spacing  Joist Size

 Maximum floor
 joist spans

 12"

 2x6

 10' 9"
 12"  2x8  14' 2"
 12"  2x10  18' 0"
 12"  2x12  21' 9"
 16"

 2x6

 9' 9"
 16"  2x8  12' 10"
 16"  2x10  16' 1"
 16"  2x12  18' 10"
 24"  2x6  8' 6"
 24"  2x8  11' 0"
 24"  2x10  13' 1"
 24"  2x12  15' 5"

 

For more information and specifications see the International Residential Code (IRC), Floor Joist Spans for Common Lumber Species.