Rafter Span Tables
Rafter spans for Southern Yellow Pine, Douglas Fir, and Eastern Spruce
Rafter span tables - Use these tables to determine lengths, sizes and spacing of rafters based on a variety of factors such as, species, load, grade, spacing and pitch. Visit the roof framing page for more information on cutting roof rafters, and visit the roof pitch calculator for determining rafter lengths based on rise and run.
For example, in the rafter span table below, the highlighted cell (in the 40# Live Load table), indicates that 2" x 8" Southern Yellow Pine joists, that have a grade of #2, that 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.
Rafter Span Tables
Use these two tables for roof rafters with a slope of 3" in 12" or less.
| Nominal Size | Spaced (o.c.) | Species / Grade ( 20# Live Load - No Finished Ceiling) | |||
| S. Pine | S. Pine | Doug. Fir | E. Spruce | ||
| #1 (kiln) | #2 grade | #2 grade | Structural | ||
| 2" x 6" | 12 | 16-5 | 14-2 | 15-4 | 14-4 |
| 16 | 14-8 | 12-4 | 13-3 | 12-10 | |
| 24 | 12-8 | 10-0 | 10-10 | 10-5 | |
| 2" x 8" | 12 | 21-7 | 18-9 | 20-3 | 19-4 |
| 16 | 19-6 | 16-3 | 17-6 | 16-10 | |
| 24 | 16-8 | 13-3 | 14-4 | 13-9 | |
| 2" x 10" | 12 | 27-6 | 23-11 | 25-10 | 24-6 |
| 16 | 24-8 | 20-8 | 22-4 | 21-6 | |
| 24 | 21-3 | 16-11 | 18-3 | 17-7 | |
| 2" x 12" | 12 | 33-5 | 29-1 | 31-4 | 30-0 |
| 16 | 30-0 | 25-2 | 27-2 | 26-2 | |
| 24 | 25-10 | 20-6 | 22-2 | 21-5 | |
| Nominal Size | Spaced (o.c.) | Species / Grade ( 40# Live Load - No Finished Ceiling) | |||
| S. Pine | S. Pine | Doug. Fir | E. Spruce | ||
| #1 (kiln) | #2 grade | #2 grade | Structural | ||
| 2" x 6" | 12 | 13-0 | 11-0 | 11-11 | 11-5 |
| 16 | 11-9 | 9-6 | 10-3 | 9-11 | |
| 24 | 9-9 | 7-9 | 8-5 | 8-1 | |
| 2" x 8" | 12 | 17-2 | 14-6 | 15-8 | 15-1 |
| 16 | 15-6 | 12-7 | 13-7 | 13-1 | |
| 24 | 12-11 | 10-3 | 11-1 | 10-8 | |
| 2" x 10" | 12 | 21-10 | 18-6 | 20-0 | 19-3 |
| 16 | 20-0 | 16-0 | 17-4 | 16-8 | |
| 24 | 16-6 | 13-1 | 14-2 | 13-7 | |
| 2" x 12" | 12 | 26-6 | 22-6 | 24-4 | 23-5 |
| 16 | 24-4 | 19-6 | 21-1 | 20-3 | |
| 24 | 20-0 | 15-11 | 17-2 | 16-7 | |
Use these two tables for roof rafters with a slope greater than 3" in 12".
| Nominal Size | Spaced (o.c.) | Species / Grade ( 20# Live Load - Light Roofing) | |||
| S. Pine | S. Pine | Doug. Fir | E. Spruce | ||
| #1 (kiln) | #2 grade | #2 grade | Structural | ||
| 2" x 4" | 12 | 11-6 | 10-3 | 11-0 | 9-11 |
| 16 | 10-5 | 9-1 | 9-6 | 8-7 | |
| 24 | 8-6 | 7-4 | 7-9 | 7-0 | |
| 2" x 6" | 12 | 18-1 | 15-0 | 16-2 | 15-7 |
| 16 | 16-4 | 13-0 | 14-0 | 13-6 | |
| 24 | 13-4 | 10-7 | 11-5 | 11-0 | |
| 2" x 8" | 12 | 23-8 | 19-9 | 21-4 | 20-6 |
| 16 | 21-6 | 17-1 | 18-5 | 17-9 | |
| 24 | 17-7 | 13-11 | 15-1 | 14-6 | |
| 2" x 10" | 12 | 30-3 | 25-2 | 27-2 | 26-2 |
| 16 | 27-5 | 21-10 | 23-7 | 22-8 | |
| 24 | 22-5 | 17-10 | 19-3 | 18-6 | |
| Nominal Size | Spaced (o.c.) | Species / Grade ( 40# Live Load - Heavy Roofing) | |||
| S. Pine | S. Pine | Doug. Fir | E. Spruce | ||
| #1 (kiln) | #2 grade | #2 grade | Structural | ||
| 2" x 4" | 12 | 8-5 | 7-4 | 7-8 | 6-11 |
| 16 | 7-3 | 6-4 | 6-8 | 6-0 | |
| 24 | 5-11 | 5-2 | 5-5 | 4-11 | |
| 2" x 6" | 12 | 13-2 | 10-6 | 11-4 | 10-11 |
| 16 | 11-5 | 9-1 | 9-10 | 9-5 | |
| 24 | 9-4 | 7-5 | 8-0 | 7-9 | |
| 2" x 8" | 12 | 17-5 | 13-10 | 14-11 | 14-5 |
| 16 | 15-1 | 12-0 | 12-11 | 12-6 | |
| 24 | 12-4 | 9-9 | 10-7 | 10-2 | |
| 2" x 10" | 12 | 22-2 | 17-8 | 19-1 | 18-4 |
| 16 | 19-3 | 15-3 | 16-6 | 15-11 | |
| 24 | 15-8 | 12-6 | 13-6 | 13-0 | |
The above spans are based on American Softwood Lumber standard sizes.
** Note: The data in the rafter span tables above were obtained from Architectural Drawing and Light Construction by Edward J. Muller.
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