These rafter spans are for #2 lumber, a ground snow load of 30 psf, the ceiling not attached to rafters, and a dead load of 10 psf. All other data can be found in the 2012 International Residential Code Rafter Spans. Be sure to use rafter clips on every rafter not nailed into a ceiling joist. Nail on a three foot collar tie every four foot to meet code requirements. Use two 12d toe nails one one side and and one on the other to firmly attach the rafter.
| O.C. | Type of Wood | 2×6 | 2×8 | 2×10 | 2×12 |
| 16″ | Southern Pine | 12’6″ | 16’2″ | 19’3″ | 22’7″ |
| Hem-Fir | 11’9″ | 14’11” | 18’2″ | 21’1″ | |
| Spruce-Pine-Fir | 11’11” | 15’1″ | 18’5″ | 21’5″ | |
| 19.2″ | Southern Pine | 11’5″ | 14’9″ | 17’7″ | 20’7″ |
| Hem-Fir | 10’9″ | 13’7″ | 16’7″ | 19’3″ | |
| Spruce-Pine-Fir | 10’11” | 13’9″ | 16’10” | 19’6″ | |
| 24″ | Southern Pine | 10’2″ | 13’2″ | 15’9″ | 18’5″ |
| Hem-Fir | 9’7″ | 12’2″ | 14’10” | 17’3″ | |
| Spruce-Pine-Fir | 9’9″ | 12’4″ | 15’1″ | 17’6″ |