// CODE SNIPPET
R802.5.1 Purlins
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Installation of purlins to reduce the span of rafters is permitted as shown in Figure R802.5.1. Purlins shall be sized not less than the required size of the rafters that they support. Purlins shall be continuous and shall be supported by 2-inch by 4-inch (51 mm by 102 mm) braces installed to bearing walls at a slope not less than 45 degrees (0.785 rad) from the horizontal. The braces shall be spaced not more than 4 feet (1219 mm) on center and the unbraced length of braces shall not exceed 8 feet (2438 mm).
RAFTER SPANS FOR COMMON LUMBER SPECIES (Roof live load=20 psf, ceiling not attached to rafters, L/Δ = 180)
| RAFTER SPACING (inches) | SPECIES AND GRADE | DEAD LOAD = 10 psf | DEAD LOAD = 20 psf | |||||||||
| 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | |||
| Maximum rafter spansa | ||||||||||||
| (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | |||
| 12 | Douglas fir-larch | SS | 11-6 | 18-0 | 23-9 | Note b | Note b | 11-6 | 18-0 | 23-9 | Note b | Note b |
| Douglas fir-larch | #1 | 11-1 | 17-4 | 22-5 | Note b | Note b | 10-6 | 15-4 | 19-5 | 23-9 | Note b | |
| Douglas fir-larch | #2 | 10-10 | 16-10 | 21-4 | 26-0 | Note b | 10-0 | 14-7 | 18-5 | 22-6 | 26-0 | |
| Douglas fir-larch | #3 | 8-9 | 12-10 | 16-3 | 19-10 | 23-0 | 7-7 | 11-1 | 14-1 | 17-2 | 19-11 | |
| Hem-fir | SS | 10-10 | 17-0 | 22-5 | Note b | Note b | 10-10 | 17-0 | 22-5 | Note b | Note b | |
| Hem-fir | #1 | 10-7 | 16-8 | 22-0 | Note b | Note b | 10-4 | 15-2 | 19-2 | 23-5 | Note b | |
| Hem-fir | #2 | 10-1 | 15-11 | 20-8 | 25-3 | Note b | 9-8 | 14-2 | 17-11 | 21-11 | 25-5 | |
| Hem-fir | #3 | 8-7 | 12-6 | 15-10 | 19-5 | 22-6 | 7-5 | 10-10 | 13-9 | 16-9 | 19-6 | |
| Southern pine | SS | 11-3 | 17-8 | 23-4 | Note b | Note b | 11-3 | 17-8 | 23-4 | Note b | Note b | |
| Southern pine | #1 | 10-10 | 17-0 | 22-5 | Note b | Note b | 10-6 | 15-8 | 19-10 | 23-2 | Note b | |
| Southern pine | #2 | 10-4 | 15-7 | 19-8 | 23-5 | Note b | 9-0 | 13-6 | 17-1 | 20-3 | 23-10 | |
| Southern pine | #3 | 8-0 | 11-9 | 14-10 | 18-0 | 21-4 | 6-11 | 10-2 | 12-10 | 15-7 | 18-6 | |
| Spruce-pine-fir | SS | 10-7 | 16-8 | 21-11 | Note b | Note b | 10-7 | 16-8 | 21-9 | Note b | Note b | |
| Spruce-pine-fir | #1 | 10-4 | 16-3 | 21-0 | 25-8 | Note b | 9-10 | 14-4 | 18-2 | 22-3 | 25-9 | |
| Spruce-pine-fir | #2 | 10-4 | 16-3 | 21-0 | 25-8 | Note b | 9-10 | 14-4 | 18-2 | 22-3 | 25-9 | |
| Spruce-pine-fir | #3 | 8-7 | 12-6 | 15-10 | 19-5 | 22-6 | 7-5 | 10-10 | 13-9 | 16-9 | 19-6 | |
| 16 | Douglas fir-larch | SS | 10-5 | 16-4 | 21-7 | Note b | Note b | 10-5 | 16-3 | 20-7 | 25-2 | Note b |
| Douglas fir-larch | #1 | 10-0 | 15-4 | 19-5 | 23-9 | Note b | 9-1 | 13-3 | 16-10 | 20-7 | 23-10 | |
| Douglas fir-larch | #2 | 9-10 | 14-7 | 18-5 | 22-6 | 26-0 | 8-7 | 12-7 | 16-0 | 19-6 | 22-7 | |
| Douglas fir-larch | #3 | 7-7 | 11-1 | 14-1 | 17-2 | 19-11 | 6-7 | 9-8 | 12-12 | 14-11 | 17-3 | |
| Hem-fir | SS | 9-10 | 15-6 | 20-5 | Note b | Note b | 9-10 | 15-6 | 19-11 | 24-4 | Note b | |
| Hem-fir | #1 | 9-8 | 15-2 | 19-2 | 23-5 | Note b | 9-0 | 13-1 | 16-7 | 20-4 | 23-7 | |
| Hem-fir | #2 | 9-2 | 14-2 | 17-11 | 21-11 | 25-5 | 8-5 | 12-3 | 15-6 | 18-11 | 22-0 | |
| Hem-fir | #3 | 7-5 | 10-10 | 13-9 | 16-9 | 19-6 | 6-5 | 9-5 | 11-11 | 14-6 | 16-10 | |
| Southern pine | SS | 10-3 | 16-1 | 21-2 | Note b | Note b | 10-3 | 16-1 | 21-2 | 25-7 | Note b | |
| Southern pine | #1 | 9-10 | 15-6 | 19-10 | 23-2 | Note b | 9-1 | 13-7 | 17-2 | 20-1 | 23-10 | |
| Southern pine | #2 | 9-0 | 13-6 | 17-1 | 20-3 | 23-10 | 7-9 | 11-8 | 14-9 | 17-6 | 20-8 | |
| Southern pine | #3 | 6-11 | 10-2 | 12-10 | 15-7 | 18-6 | 6-0 | 8-10 | 11-2 | 13-6 | 16-0 | |
| Spruce-pine-fir | SS | 9-8 | 15-2 | 19-11 | 25-5 | Note b | 9-8 | 14-10 | 18-10 | 23-0 | Note b | |
| Spruce-pine-fir | #1 | 9-5 | 14-4 | 18-2 | 22-3 | 25-9 | 8-6 | 12-5 | 15-9 | 19-3 | 22-4 | |
| Spruce-pine-fir | #2 | 9-5 | 14-4 | 18-2 | 22-3 | 25-9 | 8-6 | 12-5 | 15-9 | 19-3 | 22-4 | |
| Spruce-pine-fir | #3 | 7-5 | 10-10 | 13-9 | 16-9 | 19-6 | 6-5 | 9-5 | 11-11 | 14-6 | 16-10 | |
| 19.2 | Douglas fir-larch | SS | 9-10 | 15-5 | 20-4 | 25-11 | Note b | 9-10 | 14-10 | 18-10 | 23-0 | Note b |
| Douglas fir-larch | #1 | 9-5 | 14-0 | 17-9 | 21-8 | 25-2 | 8-4 | 12-2 | 15-4 | 18-9 | 21-9 | |
| Douglas fir-larch | #2 | 9-1 | 13-3 | 16-10 | 20-7 | 23-10 | 7-10 | 11-6 | 14-7 | 17-10 | 20-8 | |
| Douglas fir-larch | #3 | 6-11 | 10-2 | 12-10 | 15-8 | 18-3 | 6-0 | 8-9 | 11-2 | 12-7 | 15-9 | |
| Hem-fir | SS | 9-3 | 14-7 | 19-2 | 24-6 | Note b | 9-3 | 14-4 | 18-2 | 22-3 | 25-9 | |
| Hem-fir | #1 | 9-1 | 13-10 | 17-6 | 21-5 | 24-10 | 8-2 | 12-0 | 15-2 | 18-6 | 21-6 | |
| Hem-fir | #2 | 8-8 | 12-11 | 16-4 | 20-0 | 23-2 | 7-8 | 11-2 | 14-2 | 17-4 | 20-1 | |
| Hem-fir | #3 | 6-9 | 9-11 | 12-7 | 15-4 | 17-9 | 5-10 | 8-7 | 10-10 | 13-3 | 15-5 | |
| Southern pine | SS | 9-8 | 15-2 | 19-11 | 25-5 | Note b | 9-8 | 15-2 | 19-7 | 23-4 | Note b | |
| Southern pine | #1 | 9-3 | 14-3 | 18-1 | 21-2 | 25-2 | 8-4 | 12-4 | 15-8 | 18-4 | 21-9 | |
| Southern pine | #2 | 8-2 | 12-3 | 15-7 | 18-6 | 21-9 | 7-1 | 10-8 | 13-6 | 16-0 | 18-10 | |
| Southern pine | #3 | 6-4 | 9-4 | 11-9 | 14-3 | 16-10 | 5-6 | 8-1 | 10-2 | 12-4 | 14-7 | |
| Spruce-pine-fir | SS | 9-1 | 14-3 | 18-9 | 23-11 | Note b | 9-1 | 13-7 | 17-2 | 21-0 | 24-4 | |
| Spruce-pine-fir | #1 | 8-10 | 13-1 | 16-7 | 20-3 | 23-6 | 7-9 | 11-4 | 14-4 | 17-7 | 20-4 | |
| Spruce-pine-fir | #2 | 8-10 | 13-1 | 16-7 | 20-3 | 23-6 | 7-9 | 11-4 | 14-4 | 17-7 | 20-4 | |
| Spruce-pine-fir | #3 | 6-9 | 9-11 | 12-7 | 15-4 | 17-9 | 5-10 | 8-7 | 10-10 | 13-3 | 15-5 | |
| 24 | Douglas fir-larch | SS | 9-1 | 14-4 | 18-10 | 23-9 | Note b | 9-1 | 13-3 | 16-10 | 20-7 | 23-10 |
| Douglas fir-larch | #1 | 8-7 | 12-6 | 15-10 | 19-5 | 22-6 | 7-5 | 10-10 | 13-9 | 16-9 | 19-6 | |
| Douglas fir-larch | #2 | 8-2 | 11-11 | 15-1 | 18-5 | 21-4 | 7-0 | 10-4 | 13-0 | 15-11 | 18-6 | |
| Douglas fir-larch | #3 | 6-2 | 9-1 | 11-6 | 14-1 | 16-3 | 5-4 | 7-10 | 10-0 | 12-2 | 14-1 | |
| Hem-fir | SS | 8-7 | 13-6 | 17-10 | 22-9 | Note b | 8-7 | 12-10 | 16-3 | 19-10 | 23-0 | |
| Hem-fir | #1 | 8-5 | 12-4 | 15-8 | 19-2 | 22-2 | 7-4 | 10-9 | 13-7 | 16-7 | 19-3 | |
| Hem-fir | #2 | 7-11 | 11-7 | 14-8 | 17-10 | 20-9 | 6-10 | 10-0 | 12-8 | 15-6 | 17-11 | |
| Hem-fir | #3 | 6-1 | 8-10 | 11-3 | 13-8 | 15-11 | 5-3 | 7-8 | 9-9 | 11-10 | 13-9 | |
| Southern pine | SS | 8-11 | 14-1 | 18-6 | 23-8 | Note b | 8-11 | 13-10 | 17-6 | 20-10 | 24-8 | |
| Southern pine | #1 | 8-7 | 12-9 | 16-2 | 18-11 | 22-6 | 7-5 | 11-1 | 14-0 | 16-5 | 19-6 | |
| Southern pine | #2 | 7-4 | 11-0 | 13-11 | 16-6 | 19-6 | 6-4 | 9-6 | 12-1 | 14-4 | 16-10 | |
| Southern pine | #3 | 5-8 | 8-4 | 10-6 | 12-9 | 15-1 | 4-11 | 7-3 | 9-1 | 11-0 | 13-1 | |
| Spruce-pine-fir | SS | 8-5 | 13-3 | 17-5 | 21-8 | 25-2 | 8-4 | 12-2 | 15-4 | 18-9 | 21-9 | |
| Spruce-pine-fir | #1 | 8-0 | 11-9 | 14-10 | 18-2 | 21-0 | 6-11 | 10-2 | 12-10 | 15-8 | 18-3 | |
| Spruce-pine-fir | #2 | 8-0 | 11-9 | 14-10 | 18-2 | 21-0 | 6-11 | 10-2 | 12-10 | 15-8 | 18-3 | |
| Spruce-pine-fir | #3 | 6-1 | 8-10 | 11-3 | 13-8 | 15-11 | 5-3 | 7-8 | 9-9 | 11-10 | 13-9 | |
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:
HC/HR Rafter Span Adjustment Factor 1/3 0.67 1/4 0.76 1/5 0.83 1/6 0.90 1/7.5 or less 1.00 where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
- Span exceeds 26 feet in length.
RAFTER SPANS FOR COMMON LUMBER SPECIES (Roof live load=20 psf, ceiling attached to rafters, L/Δ = 240)
| RAFTER SPACING (inches) | SPECIES AND GRADE | DEAD LOAD = 10 psf | DEAD LOAD = 20 psf | |||||||||
| 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | |||
| Maximum rafter spansa | ||||||||||||
| (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | |||
| 12 | Douglas fir-larch | SS | 10-5 | 16-4 | 21-7 | Note b | Note b | 10-5 | 16-4 | 21-7 | Note b | Note b |
| Douglas fir-larch | #1 | 10-0 | 15-9 | 20-10 | Note b | Note b | 10-0 | 15-4 | 19-5 | 23-9 | Note b | |
| Douglas fir-larch | #2 | 9-10 | 15-6 | 20-5 | 26-0 | Note b | 9-10 | 14-7 | 18-5 | 22-6 | 26-0 | |
| Douglas fir-larch | #3 | 8-9 | 12-10 | 16-3 | 19-10 | 23-0 | 7-7 | 11-1 | 14-1 | 17-2 | 19-11 | |
| Hem-fir | SS | 9-10 | 15-6 | 20-5 | Note b | Note b | 9-10 | 15-6 | 20-5 | Note b | Note b | |
| Hem-fir | #1 | 9-8 | 15-2 | 19-11 | 25-5 | Note b | 9-8 | 15-2 | 19-2 | 23-5 | Note b | |
| Hem-fir | #2 | 9-2 | 14-5 | 19-0 | 24-3 | Note b | 9-2 | 14-2 | 17-11 | 21-11 | 25-5 | |
| Hem-fir | #3 | 8-7 | 12-6 | 15-10 | 19-5 | 22-6 | 7-5 | 10-10 | 13-9 | 16-9 | 19-6 | |
| Southern pine | SS | 10-3 | 16-1 | 21-2 | Note b | Note b | 10-3 | 16-1 | 21-2 | Note b | Note b | |
| Southern pine | #1 | 9-10 | 15-6 | 20-5 | Note b | Note b | 9-10 | 15-6 | 19-10 | 23-2 | Note b | |
| Southern pine | #2 | 9-5 | 14-9 | 19-6 | 23-5 | Note b | 9-0 | 13-6 | 17-1 | 20-3 | 23-10 | |
| Southern pine | #3 | 8-0 | 11-9 | 14-10 | 18-0 | 21-4 | 6-11 | 10-2 | 12-10 | 15-7 | 18-6 | |
| Spruce-pine-fir | SS | 9-8 | 15-2 | 19-11 | 25-5 | Note b | 9-8 | 15-2 | 19-11 | 25-5 | Note b | |
| Spruce-pine-fir | #1 | 9-5 | 14-9 | 19-6 | 24-10 | Note b | 9-5 | 14-4 | 18-2 | 22-3 | 25-9 | |
| Spruce-pine-fir | #2 | 9-5 | 14-9 | 19-6 | 24-10 | Note b | 9-5 | 14-4 | 18-2 | 22-3 | 25-9 | |
| Spruce-pine-fir | #3 | 8-7 | 12-6 | 15-10 | 19-5 | 22-6 | 7-5 | 10-10 | 13-9 | 16-9 | 19-6 | |
| 16 | Douglas fir-larch | SS | 9-6 | 14-11 | 19-7 | 25-0 | Note b | 9-6 | 14-11 | 19-7 | 25-0 | Note b |
| Douglas fir-larch | #1 | 9-1 | 14-4 | 18-11 | 23-9 | Note b | 9-1 | 13-3 | 16-10 | 20-7 | 23-10 | |
| Douglas fir-larch | #2 | 8-11 | 14-1 | 18-5 | 22-6 | 26-0 | 8-7 | 12-7 | 16-0 | 19-6 | 22-7 | |
| Douglas fir-larch | #3 | 7-7 | 11-1 | 14-1 | 17-2 | 19-11 | 6-7 | 9-8 | 12-2 | 14-11 | 17-3 | |
| Hem-fir | SS | 8-11 | 14-1 | 18-6 | 23-8 | Note b | 8-11 | 14-1 | 18-6 | 23-8 | Note b | |
| Hem-fir | #1 | 8-9 | 13-9 | 18-1 | 23-1 | Note b | 8-9 | 13-1 | 16-7 | 20-4 | 23-7 | |
| Hem-fir | #2 | 8-4 | 13-1 | 17-3 | 21-11 | 25-5 | 8-4 | 12-3 | 15-6 | 18-11 | 22-0 | |
| Hem-fir | #3 | 7-5 | 10-10 | 13-9 | 16-9 | 19-6 | 6-5 | 9-5 | 11-11 | 14-6 | 16-10 | |
| Southern pine | SS | 9-4 | 14-7 | 19-3 | 24-7 | Note b | 9-4 | 14-7 | 19-3 | 24-7 | Note b | |
| Southern pine | #1 | 8-11 | 14-1 | 18-6 | 23-2 | Note b | 8-11 | 13-7 | 17-2 | 20-1 | 23-10 | |
| Southern pine | #2 | 8-7 | 13-5 | 17-1 | 20-3 | 23-10 | 7-9 | 11-8 | 14-9 | 17-6 | 20-8 | |
| Southern pine | #3 | 6-11 | 10-2 | 12-10 | 15-7 | 18-6 | 6-0 | 8-10 | 11-2 | 13-6 | 16-0 | |
| Spruce-pine-fir | SS | 8-9 | 13-9 | 18-1 | 23-1 | Note b | 8-9 | 13-9 | 18-1 | 23-0 | Note b | |
| Spruce-pine-fir | #1 | 8-7 | 13-5 | 17-9 | 22-3 | 25-9 | 8-6 | 12-5 | 15-9 | 19-3 | 22-4 | |
| Spruce-pine-fir | #2 | 8-7 | 13-5 | 17-9 | 22-3 | 25-9 | 8-6 | 12-5 | 15-9 | 19-3 | 22-4 | |
| Spruce-pine-fir | #3 | 7-5 | 10-10 | 13-9 | 16-9 | 19-6 | 6-5 | 9-5 | 11-11 | 14-6 | 16-10 | |
| 19.2 | Douglas fir-larch | SS | 8-11 | 14-0 | 18-5 | 23-7 | Note b | 8-11 | 14-0 | 18-5 | 23-0 | Note b |
| Douglas fir-larch | #1 | 8-7 | 13-6 | 17-9 | 21-8 | 25-2 | 8-4 | 12-2 | 15-4 | 18-9 | 21-9 | |
| Douglas fir-larch | #2 | 8-5 | 13-3 | 16-10 | 20-7 | 23-10 | 7-10 | 11-6 | 14-7 | 17-10 | 20-8 | |
| Douglas fir-larch | #3 | 6-11 | 10-2 | 12-10 | 15-8 | 18-3 | 6-0 | 8-9 | 11-2 | 13-7 | 15-9 | |
| Hem-fir | SS | 8-5 | 13-3 | 17-5 | 22-3 | Note b | 8-5 | 13-3 | 17-5 | 22-3 | 25-9 | |
| Hem-fir | #1 | 8-3 | 12-11 | 17-1 | 21-5 | 24-10 | 8-2 | 12-0 | 15-2 | 18-6 | 21-6 | |
| Hem-fir | #2 | 7-10 | 12-4 | 16-3 | 20-0 | 23-2 | 7-8 | 11-2 | 14-2 | 17-4 | 20-1 | |
| Hem-fir | #3 | 6-9 | 9-11 | 12-7 | 15-4 | 17-9 | 5-10 | 8-7 | 10-10 | 13-3 | 15-5 | |
| Southern pine | SS | 8-9 | 13-9 | 18-2 | 23-1 | Note b | 8-9 | 13-9 | 18-2 | 23-1 | Note b | |
| Southern pine | #1 | 8-5 | 13-3 | 17-5 | 21-2 | 25-2 | 8-4 | 12-4 | 15-8 | 18-4 | 21-9 | |
| Southern pine | #2 | 8-1 | 12-3 | 15-7 | 18-6 | 21-9 | 7-1 | 10-8 | 13-6 | 16-0 | 18-10 | |
| Southern pine | #3 | 6-4 | 9-4 | 11-9 | 14-3 | 16-10 | 5-6 | 8-1 | 10-2 | 12-4 | 14-7 | |
| Spruce-pine-fir | SS | 8-3 | 12-11 | 17-1 | 21-9 | Note b | 8-3 | 12-11 | 17-1 | 21-0 | 24-4 | |
| Spruce-pine-fir | #1 | 8-1 | 12-8 | 16-7 | 20-3 | 23-6 | 7-9 | 11-4 | 14-4 | 17-7 | 20-4 | |
| Spruce-pine-fir | #2 | 8-1 | 12-8 | 16-7 | 20-3 | 23-6 | 7-9 | 11-4 | 14-4 | 17-7 | 20-4 | |
| Spruce-pine-fir | #3 | 6-9 | 9-11 | 12-7 | 15-4 | 17-9 | 5-10 | 8-7 | 10-10 | 13-3 | 15-5 | |
| 24 | Douglas fir-larch | SS | 8-3 | 13-0 | 17-2 | 21-10 | Note b | 8-3 | 13-0 | 16-10 | 20-7 | 23-10 |
| Douglas fir-larch | #1 | 8-0 | 12-6 | 15-10 | 19-5 | 22-6 | 7-5 | 10-10 | 13-9 | 16-9 | 19-6 | |
| Douglas fir-larch | #2 | 7-10 | 11-11 | 15-1 | 18-5 | 21-4 | 7-0 | 10-4 | 13-0 | 15-11 | 18-6 | |
| Douglas fir-larch | #3 | 6-2 | 9-1 | 11-6 | 14-1 | 16-3 | 5-4 | 7-10 | 10-0 | 12-2 | 14-1 | |
| Hem-fir | SS | 7-10 | 12-3 | 16-2 | 20-8 | 25-1 | 7-10 | 12-3 | 16-2 | 19-10 | 23-0 | |
| Hem-fir | #1 | 7-8 | 12-0 | 15-8 | 19-2 | 22-2 | 7-4 | 10-9 | 13-7 | 16-7 | 19-3 | |
| Hem-fir | #2 | 7-3 | 11-5 | 14-8 | 17-10 | 20-9 | 6-10 | 10-0 | 12-8 | 15-6 | 17-11 | |
| Hem-fir | #3 | 6-1 | 8-10 | 11-3 | 13-8 | 15-11 | 5-3 | 7-8 | 9-9 | 11-10 | 13-9 | |
| Southern pine | SS | 8-1 | 12-9 | 16-10 | 21-6 | Note b | 8-1 | 12-9 | 16-10 | 20-10 | 24-8 | |
| Southern pine | #1 | 7-10 | 12-3 | 16-2 | 18-11 | 22-6 | 7-5 | 11-1 | 14-0 | 16-5 | 19-6 | |
| Southern pine | #2 | 7-4 | 11-0 | 13-11 | 16-6 | 19-6 | 6-4 | 9-6 | 12-1 | 14-4 | 16-10 | |
| Southern pine | #3 | 5-8 | 8-4 | 10-6 | 12-9 | 15-1 | 4-11 | 7-3 | 9-1 | 11-0 | 13-1 | |
| Spruce-pine-fir | SS | 7-8 | 12-0 | 15-10 | 20-2 | 24-7 | 7-8 | 12-0 | 15-4 | 18-9 | 21-9 | |
| Spruce-pine-fir | #1 | 7-6 | 11-9 | 14-10 | 18-2 | 21-0 | 6-11 | 10-2 | 12-10 | 15-8 | 18-3 | |
| Spruce-pine-fir | #2 | 7-6 | 11-9 | 14-10 | 18-2 | 21-0 | 6-11 | 10-2 | 12-10 | 15-8 | 18-3 | |
| Spruce-pine-fir | #3 | 6-1 | 8-10 | 11-3 | 13-8 | 15-11 | 5-3 | 7-8 | 9-9 | 11-10 | 13-9 | |
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the following factors:
HC/HR Rafter Span Adjustment Factor 1/3 0.67 1/4 0.76 1/5 0.83 1/6 0.90 1/7.5 or less 1.00 where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
- Span exceeds 26 feet in length.
RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=30 psf, ceiling not attached to rafters, L/Δ = 180)
| RAFTER SPACING (inches) | SPECIES AND GRADE | DEAD LOAD = 10 psf | DEAD LOAD = 20 psf | |||||||||
| 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | |||
| Maximum rafter spansa | ||||||||||||
| (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | |||
| 12 | Douglas fir-larch | SS | 10-0 | 15-9 | 20-9 | Note b | Note b | 10-0 | 15-9 | 20-5 | 24-11 | Note b |
| Douglas fir-larch | #1 | 9-8 | 14-9 | 18-8 | 22-9 | Note b | 9-0 | 13-2 | 16-8 | 20-4 | 23-7 | |
| Douglas fir-larch | #2 | 9-6 | 14-0 | 17-8 | 21-7 | 25-1 | 8-6 | 12-6 | 15-10 | 19-4 | 22-5 | |
| Douglas fir-larch | #3 | 7-3 | 10-8 | 13-6 | 16-6 | 19-2 | 6-6 | 9-6 | 12-1 | 14-9 | 17-1 | |
| Hem-fir | SS | 9-6 | 14-10 | 19-7 | 25-0 | Note b | 9-6 | 14-10 | 19-7 | 24-1 | Note b | |
| Hem-fir | #1 | 9-3 | 14-6 | 18-5 | 22-6 | 26-0 | 8-11 | 13-0 | 16-6 | 20-1 | 23-4 | |
| Hem-fir | #2 | 8-10 | 13-7 | 17-2 | 21-0 | 24-4 | 8-4 | 12-2 | 15-4 | 18-9 | 21-9 | |
| Hem-fir | #3 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | 6-4 | 9-4 | 11-9 | 14-5 | 16-8 | |
| Southern pine | SS | 9-10 | 15-6 | 20-5 | Note b | Note b | 9-10 | 15-6 | 20-5 | 25-4 | Note b | |
| Southern pine | #1 | 9-6 | 14-10 | 19-0 | 22-3 | Note b | 9-0 | 13-5 | 17-0 | 19-11 | 23-7 | |
| Southern pine | #2 | 8-7 | 12-11 | 16-4 | 19-5 | 22-10 | 7-8 | 11-7 | 14-8 | 17-4 | 20-5 | |
| Southern pine | #3 | 6-7 | 9-9 | 12-4 | 15-0 | 17-9 | 5-11 | 8-9 | 11-0 | 13-5 | 15-10 | |
| Spruce-pine-fir | SS | 9-3 | 14-7 | 19-2 | 24-6 | Note b | 9-3 | 14-7 | 18-8 | 22-9 | Note b | |
| Spruce-pine-fir | #1 | 9-1 | 13-9 | 17-5 | 21-4 | 24-8 | 8-5 | 12-4 | 15-7 | 19-1 | 22-1 | |
| Spruce-pine-fir | #2 | 9-1 | 13-9 | 17-5 | 21-4 | 24-8 | 8-5 | 12-4 | 15-7 | 19-1 | 22-1 | |
| Spruce-pine-fir | #3 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | 6-4 | 9-4 | 11-9 | 14-5 | 16-8 | |
| 16 | Douglas fir-larch | SS | 9-1 | 14-4 | 18-10 | 24-1 | Note b | 9-1 | 14-0 | 17-8 | 21-7 | 25-1 |
| Douglas fir-larch | #1 | 8-9 | 12-9 | 16-2 | 19-9 | 22-10 | 7-10 | 11-5 | 14-5 | 17-8 | 20-5 | |
| Douglas fir-larch | #2 | 8-3 | 12-1 | 15-4 | 18-9 | 21-8 | 7-5 | 10-10 | 13-8 | 16-9 | 19-5 | |
| Douglas fir-larch | #3 | 6-4 | 9-3 | 11-8 | 14-3 | 16-7 | 5-8 | 8-3 | 10-6 | 12-9 | 14-10 | |
| Hem-fir | SS | 8-7 | 13-6 | 17-10 | 22-9 | Note b | 8-7 | 13-6 | 17-1 | 20-10 | 24-2 | |
| Hem-fir | #1 | 8-5 | 12-7 | 15-11 | 19-6 | 22-7 | 7-8 | 11-3 | 14-3 | 17-5 | 20-2 | |
| Hem-fir | #2 | 8-0 | 11-9 | 14-11 | 18-2 | 21-1 | 7-2 | 10-6 | 13-4 | 16-3 | 18-10 | |
| Hem-fir | #3 | 6-2 | 9-0 | 11-5 | 13-11 | 16-2 | 5-6 | 8-1 | 10-3 | 12-6 | 14-6 | |
| Southern pine | SS | 8-11 | 14-1 | 18-6 | 23-8 | Note b | 8-11 | 14-1 | 18-5 | 1-11 | 25-11 | |
| Southern pine | #1 | 8-7 | 13-0 | 16-6 | 19-3 | 22-10 | 7-10 | 11-7 | 14-9 | 17-3 | 20-5 | |
| Southern pine | #2 | 7-6 | 11-2 | 14-2 | 16-10 | 19-10 | 6-8 | 10-0 | 12-8 | 15-1 | 17-9 | |
| Southern pine | #3 | 5-9 | 8-6 | 10-8 | 13-0 | 15-4 | 5-2 | 7-7 | 9-7 | 11-7 | 13-9 | |
| Spruce-pine-fir | SS | 8-5 | 13-3 | 17-5 | 22-1 | 25-7 | 8-5 | 12-9 | 16-2 | 19-9 | 22-10 | |
| Spruce-pine-fir | #1 | 8-2 | 11-11 | 15-1 | 18-5 | 21-5 | 7-3 | 10-8 | 13-6 | 16-6 | 19-2 | |
| Spruce-pine-fir | #2 | 8-2 | 11-11 | 15-1 | 18-5 | 21-5 | 7-3 | 10-8 | 13-6 | 16-6 | 19-2 | |
| Spruce-pine-fir | #3 | 6-2 | 9-0 | 11-5 | 13-11 | 16-2 | 5-6 | 8-1 | 10-3 | 12-6 | 14-6 | |
| 19.2 | Douglas fir-larch | SS | 8-7 | 13-6 | 17-9 | 22-1 | 25-7 | 8-7 | 12-9 | 16-2 | 19-9 | 22-10 |
| Douglas fir-larch | #1 | 7-11 | 11-8 | 14-9 | 18-0 | 20-11 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | |
| Douglas fir-larch | #2 | 7-7 | 11-0 | 14-0 | 17-1 | 19-10 | 6-9 | 9-10 | 12-6 | 15-3 | 17-9 | |
| Douglas fir-larch | #3 | 5-9 | 8-5 | 10-8 | 13-1 | 15-2 | 5-2 | 7-7 | 9-7 | 11-8 | 13-6 | |
| Hem-fir | SS | 8-1 | 12-9 | 16-9 | 21-4 | 24-8 | 8-1 | 12-4 | 15-7 | 19-1 | 22-1 | |
| Hem-fir | #1 | 7-10 | 11-6 | 14-7 | 17-9 | 20-7 | 7-0 | 10-3 | 13-0 | 15-11 | 18-5 | |
| Hem-fir | #2 | 7-4 | 10-9 | 13-7 | 16-7 | 19-3 | 6-7 | 9-7 | 12-2 | 14-10 | 17-3 | |
| Hem-fir | #3 | 5-7 | 8-3 | 10-5 | 12-9 | 14-9 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | |
| Southern pine | SS | 8-5 | 13-3 | 17-5 | 22-3 | Note b | 8-5 | 13-3 | 16-10 | 20-0 | 23-7 | |
| Southern pine | #1 | 8-0 | 11-10 | 15-1 | 17-7 | 20-11 | 7-1 | 10-7 | 13-5 | 15-9 | 18-8 | |
| Southern pine | #2 | 6-10 | 10-2 | 12-11 | 15-4 | 18-1 | 6-1 | 9-2 | 11-7 | 13-9 | 16-2 | |
| Southern pine | #3 | 5-3 | 7-9 | 9-9 | 11-10 | 14-0 | 4-8 | 6-11 | 8-9 | 10-7 | 12-6 | |
| Spruce-pine-fir | SS | 7-11 | 12-5 | 16-5 | 20-2 | 23-4 | 7-11 | 11-8 | 14-9 | 18-0 | 20-11 | |
| Spruce-pine-fir | #1 | 7-5 | 10-11 | 13-9 | 16-10 | 19-6 | 6-8 | 9-9 | 12-4 | 15-1 | 17-6 | |
| Spruce-pine-fir | #2 | 7-5 | 10-11 | 13-9 | 16-10 | 19-6 | 6-8 | 9-9 | 12-4 | 15-1 | 17-6 | |
| Spruce-pine-fir | #3 | 5-7 | 8-3 | 10-5 | 12-9 | 14-9 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | |
| 24 | Douglas fir-larch | SS | 8-0 | 12-6 | 16-2 | 19-9 | 22-10 | 7-10 | 11-5 | 14-5 | 17-8 | 20-5 |
| Douglas fir-larch | #1 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | 6-4 | 9-4 | 11-9 | 14-5 | 16-8 | |
| Douglas fir-larch | #2 | 6-9 | 9-10 | 12-6 | 15-3 | 17-9 | 6-0 | 8-10 | 11-2 | 13-8 | 15-10 | |
| Douglas fir-larch | #3 | 5-2 | 7-7 | 9-7 | 11-8 | 13-6 | 4-7 | 6-9 | 8-7 | 10-5 | 12-1 | |
| Hem-fir | SS | 7-6 | 11-10 | 15-7 | 19-1 | 22-1 | 7-6 | 11-0 | 13-11 | 17-0 | 19-9 | |
| Hem-fir | #1 | 7-0 | 10-3 | 13-0 | 15-11 | 18-5 | 6-3 | 9-2 | 11-8 | 14-3 | 16-6 | |
| Hem-fir | #2 | 6-7 | 9-7 | 12-2 | 14-10 | 17-3 | 5-10 | 8-7 | 10-10 | 13-3 | 15-5 | |
| Hem-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-6 | 6-7 | 8-4 | 10-2 | 11-10 | |
| Southern pine | SS | 7-10 | 12-3 | 16-2 | 20-0 | 23-7 | 7-10 | 11-10 | 15-0 | 17-11 | 21-2 | |
| Southern pine | #1 | 7-1 | 10-7 | 13-5 | 15-9 | 18-8 | 6-4 | 9-6 | 12-0 | 14-1 | 16-8 | |
| Southern pine | #2 | 6-1 | 9-2 | 11-7 | 13-9 | 16-2 | 5-5 | 8-2 | 10-4 | 12-3 | 14-6 | |
| Southern pine | #3 | 4-8 | 6-11 | 8-9 | 10-7 | 12-6 | 4-2 | 6-2 | 7-10 | 9-6 | 11-2 | |
| Spruce-pine-fir | SS | 7-4 | 11-7 | 14-9 | 18-0 | 20-11 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | |
| Spruce-pine-fir | #1 | 6-8 | 9-9 | 12-4 | 15-1 | 17-6 | 5-11 | 8-8 | 11-0 | 13-6 | 15-7 | |
| Spruce-pine-fir | #2 | 6-8 | 9-9 | 12-4 | 15-1 | 17-6 | 5-11 | 8-8 | 11-0 | 13-6 | 15-7 | |
| Spruce-pine-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-6 | 6-7 | 8-4 | 10-2 | 11-10 | |
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:
HC/HR Rafter Span Adjustment Factor 1/3 0.67 1/4 0.76 1/5 0.83 1/6 0.90 1/7.5 or less 1.00 where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
- Span exceeds 26 feet in length.
RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=50 psf, ceiling not attached to rafters, L/Δ = 180)
| RAFTER SPACING (inches) | SPECIES AND GRADE | DEAD LOAD = 10 psf | DEAD LOAD = 20 psf | |||||||||
| 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | |||
| Maximum rafter spansa | ||||||||||||
| (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | |||
| 12 | Douglas fir-larch | SS | 8-5 | 13-3 | 17-6 | 22-4 | 26-0 | 8-5 | 13-3 | 17-3 | 21-1 | 24-5 |
| Douglas fir-larch | #1 | 8-2 | 12-0 | 15-3 | 18-7 | 21-7 | 7-7 | 11-2 | 14-1 | 17-3 | 20-0 | |
| Douglas fir-larch | #2 | 7-10 | 11-5 | 14-5 | 17-8 | 20-5 | 7-3 | 10-7 | 13-4 | 16-4 | 18-11 | |
| Douglas fir-larch | #3 | 6-0 | 8-9 | 11-0 | 13-6 | 15-7 | 5-6 | 8-1 | 10-3 | 12-6 | 14-6 | |
| Hem-fir | SS | 8-0 | 12-6 | 16-6 | 21-1 | 25-6 | 8-0 | 12-6 | 16-6 | 20-4 | 23-7 | |
| Hem-fir | #1 | 7-10 | 11-10 | 15-0 | 18-4 | 21-3 | 7-6 | 11-0 | 13-11 | 17-0 | 19-9 | |
| Hem-fir | #2 | 7-5 | 11-1 | 14-0 | 17-2 | 19-11 | 7-0 | 10-3 | 13-0 | 15-10 | 18-5 | |
| Hem-fir | #3 | 5-10 | 8-6 | 10-9 | 13-2 | 15-3 | 5-5 | 7-10 | 10-0 | 12-2 | 14-1 | |
| Southern pine | SS | 8-4 | 13-1 | 17-2 | 21-11 | Note b | 8-4 | 13-1 | 17-2 | 21-5 | 25-3 | |
| Southern pine | #1 | 8-0 | 12-3 | 15-6 | 18-2 | 21-7 | 7-7 | 11-4 | 14-5 | 16-10 | 20-0 | |
| Southern pine | #2 | 7-0 | 10-6 | 13-4 | 15-10 | 18-8 | 6-6 | 9-9 | 12-4 | 14-8 | 17-3 | |
| Southern pine | #3 | 5-5 | 8-0 | 10-1 | 12-3 | 14-6 | 5-0 | 7-5 | 9-4 | 11-4 | 13-5 | |
| Spruce-pine-fir | SS | 7-10 | 12-3 | 16-2 | 20-8 | 24-1 | 7-10 | 12-3 | 15-9 | 19-3 | 22-4 | |
| Spruce-pine-fir | #1 | 7-8 | 11-3 | 14-3 | 17-5 | 20-2 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | |
| Spruce-pine-fir | #2 | 7-8 | 11-3 | 14-3 | 17-5 | 20-2 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | |
| Spruce-pine-fir | #3 | 5-10 | 8-6 | 10-9 | 13-2 | 15-3 | 5-5 | 7-10 | 10-0 | 12-2 | 14-1 | |
| 16 | Douglas fir-larch | SS | 7-8 | 12-1 | 15-11 | 19-9 | 22-10 | 7-8 | 11-10 | 14-11 | 18-3 | 21-2 |
| Douglas fir-larch | #1 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | 6-7 | 9-8 | 12-2 | 14-11 | 17-3 | |
| Douglas fir-larch | #2 | 6-9 | 9-10 | 12-6 | 15-3 | 17-9 | 6-3 | 9-2 | 11-7 | 14-2 | 16-5 | |
| Douglas fir-larch | #3 | 5-2 | 7-7 | 9-7 | 11-18 | 13-6 | 4-9 | 7-0 | 8-10 | 10-10 | 12-6 | |
| Hem-fir | SS | 7-3 | 11-5 | 15-0 | 19-1 | 22-1 | 7-3 | 11-5 | 14-5 | 17-8 | 20-5 | |
| Hem-fir | #1 | 7-0 | 10-3 | 13-0 | 15-11 | 18-5 | 6-6 | 9-6 | 12-1 | 14-9 | 17-1 | |
| Hem-fir | #2 | 6-7 | 9-7 | 12-2 | 14-10 | 17-3 | 6-1 | 8-11 | 11-3 | 13-9 | 15-11 | |
| Hem-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-8 | 6-10 | 8-8 | 10-6 | 12-3 | |
| Southern pine | SS | 7-6 | 11-10 | 15-7 | 19-11 | 23-7 | 7-6 | 11-10 | 15-7 | 18-6 | 21-10 | |
| Southern pine | #1 | 7-1 | 10-7 | 13-5 | 15-9 | 18-8 | 6-7 | 9-10 | 12-5 | 14-7 | 17-3 | |
| Southern pine | #2 | 6-1 | 9-2 | 11-7 | 13-9 | 16-2 | 5-8 | 8-5 | 10-9 | 12-9 | 15-0 | |
| Southern pine | #3 | 4-8 | 6-11 | 8-9 | 10-7 | 12-6 | 4-4 | 6-5 | 8-1 | 9-10 | 11-7 | |
| Spruce-pine-fir | SS | 7-1 | 11-2 | 14-8 | 18-0 | 20-11 | 7-1 | 10-9 | 13-8 | 15-11 | 19-4 | |
| Spruce-pine-fir | #1 | 6-8 | 9-9 | 12-4 | 15-1 | 17-6 | 6-2 | 9-0 | 11-5 | 13-11 | 16-2 | |
| Spruce-pine-fir | #2 | 6-8 | 9-9 | 12-4 | 15-1 | 17-6 | 6-2 | 9-0 | 11-5 | 13-11 | 16-2 | |
| Spruce-pine-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-8 | 6-10 | 8-8 | 10-6 | 12-3 | |
| 19.2 | Douglas fir-larch | SS | 7-3 | 11-4 | 14-9 | 18-0 | 20-11 | 7-3 | 10-9 | 13-8 | 16-8 | 19-4 |
| Douglas fir-larch | #1 | 6-6 | 9-6 | 12-0 | 14-8 | 17-1 | 6-0 | 8-10 | 11-2 | 13-7 | 15-9 | |
| Douglas fir-larch | #2 | 6-2 | 9-0 | 11-5 | 13-11 | 16-2 | 5-8 | 8-4 | 10-9 | 12-11 | 15-0 | |
| Douglas fir-larch | #3 | 4-8 | 6-11 | 8-9 | 10-8 | 12-4 | 4-4 | 6-4 | 8-1 | 9-10 | 11-5 | |
| Hem-fir | SS | 6-10 | 10-9 | 14-2 | 17-5 | 20-2 | 6-10 | 10-5 | 13-2 | 16-1 | 18-8 | |
| Hem-fir | #1 | 6-5 | 9-5 | 11-11 | 14-6 | 16-10 | 8-11 | 8-8 | 11-0 | 13-5 | 15-7 | |
| Hem-fir | #2 | 6-0 | 8-9 | 11-1 | 13-7 | 15-9 | 5-7 | 8-1 | 10-3 | 12-7 | 14-7 | |
| Hem-fir | #3 | 4-7 | 6-9 | 8-6 | 10-5 | 12-1 | 4-3 | 6-3 | 7-11 | 9-7 | 11-2 | |
| Southern pine | SS | 7-1 | 11-2 | 14-8 | 18-3 | 21-7 | 7-1 | 11-2 | 14-2 | 16-11 | 20-0 | |
| Southern pine | #1 | 6-6 | 9-8 | 12-3 | 14-4 | 17-1 | 6-0 | 9-0 | 11-4 | 13-4 | 15-9 | |
| Southern pine | #2 | 5-7 | 8-4 | 10-7 | 12-6 | 14-9 | 5-2 | 7-9 | 9-9 | 11-7 | 13-8 | |
| Southern pine | #3 | 4-3 | 6-4 | 8-0 | 9-8 | 11-5 | 4-0 | 5-10 | 7-4 | 8-11 | 10-7 | |
| Spruce-pine-fir | SS | 6-8 | 10-6 | 13-5 | 16-5 | 19-1 | 6-8 | 9-10 | 12-5 | 15-3 | 17-8 | |
| Spruce-pine-fir | #1 | 6-1 | 8-11 | 11-3 | 13-9 | 15-11 | 5-7 | 8-3 | 10-5 | 12-9 | 14-9 | |
| Spruce-pine-fir | #2 | 6-1 | 8-11 | 11-3 | 13-9 | 15-11 | 5-7 | 8-3 | 10-5 | 12-9 | 14-9 | |
| Spruce-pine-fir | #3 | 4-7 | 6-9 | 8-6 | 10-5 | 12-1 | 4-3 | 6-3 | 7-11 | 9-7 | 11-2 | |
| 24 | Douglas fir-larch | SS | 6-8 | 10-5 | 13-2 | 16-1 | 18-8 | 6-7 | 9-8 | 12-2 | 14-11 | 17-3 |
| Douglas fir-larch | #1 | 5-10 | 8-6 | 10-9 | 13-2 | 15-3 | 5-5 | 7-10 | 10-0 | 12-2 | 14-1 | |
| Douglas fir-larch | #2 | 5-6 | 8-1 | 10-3 | 12-6 | 14-6 | 5-1 | 7-6 | 9-5 | 11-7 | 13-5 | |
| Douglas fir-larch | #3 | 4-3 | 6-2 | 7-10 | 9-6 | 11-1 | 3-11 | 5-8 | 7-3 | 8-10 | 10-3 | |
| Hem-fir | SS | 6-4 | 9-11 | 12-9 | 15-7 | 18-0 | 6-4 | 9-4 | 11-9 | 14-5 | 16-8 | |
| Hem-fir | #1 | 5-9 | 8-5 | 10-8 | 13-0 | 15-1 | 8-4 | 7-9 | 9-10 | 12-0 | 13-11 | |
| Hem-fir | #2 | 5-4 | 7-10 | 9-11 | 12-1 | 14-1 | 4-11 | 7-3 | 9-2 | 11-3 | 13-0 | |
| Hem-fir | #3 | 4-1 | 6-0 | 7-7 | 9-4 | 10-9 | 3-10 | 5-7 | 7-1 | 8-7 | 10-0 | |
| Southern pine | SS | 6-7 | 10-4 | 13-8 | 16-4 | 19-3 | 6-7 | 10-0 | 12-8 | 15-2 | 17-10 | |
| Southern pine | #1 | 5-10 | 8-8 | 11-0 | 12-10 | 15-3 | 5-5 | 8-0 | 10-2 | 11-11 | 14-1 | |
| Southern pine | #2 | 5-0 | 7-5 | 9-5 | 11-3 | 13-2 | 4-7 | 6-11 | 8-9 | 10-5 | 12-3 | |
| Southern pine | #3 | 3-10 | 5-8 | 7-1 | 8-8 | 10-3 | 3-6 | 5-3 | 6-7 | 8-0 | 9-6 | |
| Spruce-pine-fir | SS | 6-2 | 9-6 | 12-0 | 14-8 | 17-1 | 6-0 | 8-10 | 11-2 | 13-7 | 15-9 | |
| Spruce-pine-fir | #1 | 5-5 | 7-11 | 10-1 | 12-4 | 14-3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | |
| Spruce-pine-fir | #2 | 5-5 | 7-11 | 10-1 | 12-4 | 14-3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | |
| Spruce-pine-fir | #3 | 4-1 | 6-0 | 7-7 | 9-4 | 10-9 | 3-10 | 5-7 | 7-1 | 8-7 | 10-0 | |
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa
The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:
HC/HR Rafter Span Adjustment Factor 1/3 0.67 1/4 0.76 1/5 0.83 1/6 0.90 1/7.5 or less 1.00 where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
- Span exceeds 26 feet in length.
RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=30 psf, ceiling attached to rafters, L/Δ = 240)
| RAFTER SPACING (inches) | SPECIES AND GRADE | DEAD LOAD = 10 psf | DEAD LOAD = 20 psf | |||||||||
| 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | |||
| Maximum rafter spansa | ||||||||||||
| (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | |||
| 12 | Douglas fir-larch | SS | 9-1 | 14-4 | 18-10 | 24-1 | Note b | 9-1 | 14-4 | 18-10 | 24-1 | Note b |
| Douglas fir-larch | #1 | 8-9 | 13-9 | 18-2 | 22-9 | Note b | 8-9 | 13-2 | 16-8 | 20-4 | 23-7 | |
| Douglas fir-larch | #2 | 8-7 | 13-6 | 17-8 | 21-7 | 25-1 | 8-6 | 12-6 | 15-10 | 19-4 | 22-5 | |
| Douglas fir-larch | #3 | 7-3 | 10-8 | 13-6 | 16-6 | 19-2 | 6-6 | 9-6 | 12-1 | 14-9 | 17-1 | |
| Hem-fir | SS | 8-7 | 13-6 | 17-10 | 22-9 | Note b | 8-7 | 13-6 | 17-10 | 22-9 | Note b | |
| Hem-fir | #1 | 8-5 | 13-3 | 17-5 | 22-3 | 26-0 | 8-5 | 13-0 | 16-6 | 20-1 | 23-4 | |
| Hem-fir | #2 | 8-0 | 12-7 | 16-7 | 21-0 | 24-4 | 8-0 | 12-2 | 15-4 | 18-9 | 21-9 | |
| Hem-fir | #3 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | 6-4 | 9-4 | 11-9 | 14-5 | 16-8 | |
| Southern pine | SS | 8-11 | 14-1 | 18-6 | 23-8 | Note b | 8-11 | 14-1 | 18-6 | 23-8 | Note b | |
| Southern pine | #1 | 8-7 | 13-6 | 17-10 | 22-3 | Note b | 8-7 | 13-5 | 17-0 | 19-11 | 23-7 | |
| Southern pine | #2 | 8-3 | 12-11 | 16-4 | 19-5 | 22-10 | 7-8 | 11-7 | 14-8 | 17-4 | 20-5 | |
| Southern pine | #3 | 6-7 | 9-9 | 12-4 | 15-0 | 17-9 | 5-11 | 8-9 | 11-0 | 13-5 | 15-10 | |
| Spruce-pine-fir | SS | 8-5 | 13-3 | 17-5 | 22-3 | Note b | 8-5 | 13-3 | 17-5 | 22-3 | Note b | |
| Spruce-pine-fir | #1 | 8-3 | 12-11 | 17-0 | 21-4 | 24-8 | 8-3 | 12-4 | 15-7 | 19-1 | 22-1 | |
| Spruce-pine-fir | #2 | 8-3 | 12-11 | 17-0 | 21-4 | 24-8 | 8-3 | 12-4 | 15-7 | 19-1 | 22-1 | |
| Spruce-pine-fir | #3 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | 6-4 | 9-4 | 11-9 | 14-5 | 16-8 | |
| 16 | Douglas fir-larch | SS | 8-3 | 13-0 | 17-2 | 21-10 | Note b | 8-3 | 13-0 | 17-2 | 21-7 | 25-1 |
| Douglas fir-larch | #1 | 8-0 | 12-6 | 16-2 | 19-9 | 22-10 | 7-10 | 11-5 | 14-5 | 17-8 | 20-5 | |
| Douglas fir-larch | #2 | 7-10 | 12-1 | 15-4 | 18-9 | 21-8 | 7-5 | 10-10 | 13-8 | 16-9 | 19-5 | |
| Douglas fir-larch | #3 | 6-4 | 9-3 | 11-8 | 14-3 | 16-7 | 5-8 | 8-3 | 10-6 | 12-9 | 14-10 | |
| Hem-fir | SS | 7-10 | 12-3 | 16-2 | 20-8 | 25-1 | 7-10 | 12-3 | 16-2 | 20-8 | 24-2 | |
| Hem-fir | #1 | 7-8 | 12-0 | 15-10 | 19-6 | 22-7 | 7-8 | 11-3 | 14-3 | 17-5 | 20-2 | |
| Hem-fir | #2 | 7-3 | 11-5 | 14-11 | 18-2 | 21-1 | 7-2 | 10-6 | 13-4 | 16-3 | 18-10 | |
| Hem-fir | #3 | 6-2 | 9-0 | 11-5 | 13-11 | 16-2 | 5-6 | 8-1 | 10-3 | 12-6 | 14-6 | |
| Southern pine | SS | 8-1 | 12-9 | 16-10 | 21-6 | Note b | 8-1 | 12-9 | 16-10 | 21-6 | 25-11 | |
| Southern pine | #1 | 7-10 | 12-3 | 16-2 | 19-3 | 22-10 | 7-10 | 11-7 | 14-9 | 17-3 | 20-5 | |
| Southern pine | #2 | 7-6 | 11-2 | 14-2 | 16-10 | 19-10 | 6-8 | 10-0 | 12-8 | 15-1 | 17-9 | |
| Southern pine | #3 | 5-9 | 8-6 | 10-8 | 13-0 | 15-4 | 5-2 | 7-7 | 9-7 | 11-7 | 13-9 | |
| Spruce-pine-fir | SS | 7-8 | 12-0 | 15-10 | 20-2 | 24-7 | 7-8 | 12-0 | 15-10 | 19-9 | 22-10 | |
| Spruce-pine-fir | #1 | 7-6 | 11-9 | 15-1 | 18-5 | 21-5 | 7-3 | 10-8 | 13-6 | 16-6 | 19-2 | |
| Spruce-pine-fir | #2 | 7-6 | 11-9 | 15-1 | 18-5 | 21-5 | 7-3 | 10-8 | 13-6 | 16-6 | 19-2 | |
| Spruce-pine-fir | #3 | 6-2 | 9-0 | 11-5 | 13-11 | 16-2 | 5-6 | 8-1 | 10-3 | 12-6 | 14-6 | |
| 19.2 | Douglas fir-larch | SS | 7-9 | 12-3 | 16-1 | 20-7 | 25-0 | 7-9 | 12-3 | 16-1 | 19-9 | 22-10 |
| Douglas fir-larch | #1 | 7-6 | 11-8 | 14-9 | 18-0 | 20-11 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | |
| Douglas fir-larch | #2 | 7-4 | 11-0 | 14-0 | 17-1 | 19-10 | 6-9 | 9-1 | 12-6 | 15-3 | 17-9 | |
| Douglas fir-larch | #3 | 5-9 | 8-5 | 10-8 | 13-1 | 15-2 | 5-2 | 7-7 | 9-7 | 11-8 | 13-6 | |
| Hem-fir | SS | 7-4 | 11-7 | 15-3 | 19-5 | 23-7 | 7-4 | 11-7 | 15-3 | 19-1 | 22-1 | |
| Hem-fir | #1 | 7-2 | 11-4 | 14-7 | 17-9 | 20-7 | 7-0 | 16-3 | 13-0 | 15-11 | 18-5 | |
| Hem-fir | #2 | 6-10 | 10-9 | 13-7 | 16-7 | 19-3 | 6-7 | 9-7 | 12-2 | 14-10 | 17-3 | |
| Hem-fir | #3 | 5-7 | 8-3 | 10-5 | 12-9 | 14-9 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | |
| Southern pine | SS | 7-8 | 12-0 | 15-10 | 20-2 | 24-7 | 7-8 | 12-0 | 15-10 | 20-0 | 23-7 | |
| Southern pine | #1 | 7-4 | 11-7 | 15-1 | 17-7 | 20-11 | 7-1 | 10-7 | 13-5 | 15-9 | 18-8 | |
| Southern pine | #2 | 6-10 | 10-2 | 12-11 | 15-4 | 18-1 | 6-1 | 9-2 | 11-7 | 13-9 | 16-2 | |
| Southern pine | #3 | 5-3 | 7-9 | 9-9 | 11-10 | 14-0 | 4-8 | 6-11 | 8-9 | 10-7 | 12-6 | |
| Spruce-pine-fir | SS | 7-2 | 11-4 | 14-11 | 19-0 | 23-1 | 7-2 | 11-4 | 14-9 | 18-0 | 20-11 | |
| Spruce-pine-fir | #1 | 7-0 | 10-11 | 13-9 | 16-10 | 19-6 | 6-8 | 9-9 | 12-4 | 15-1 | 17-6 | |
| Spruce-pine-fir | #2 | 7-0 | 10-11 | 13-9 | 16-10 | 19-6 | 6-8 | 9-9 | 12-4 | 15-1 | 17-6 | |
| Spruce-pine-fir | #3 | 5-7 | 8-3 | 10-5 | 12-9 | 14-9 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | |
| 24 | Douglas fir-larch | SS | 7-3 | 11-4 | 15-0 | 19-1 | 22-10 | 7-3 | 11-4 | 14-5 | 17-8 | 20-5 |
| Douglas fir-larch | #1 | 7-0 | 10-5 | 13-2 | 16-1 | 18-8 | 6-4 | 9-4 | 11-9 | 14-5 | 16-8 | |
| Douglas fir-larch | #2 | 6-9 | 9-10 | 12-6 | 15-3 | 17-9 | 6-0 | 8-10 | 11-2 | 13-8 | 15-10 | |
| Douglas fir-larch | #3 | 5-2 | 7-7 | 9-7 | 11-8 | 13-6 | 4-7 | 6-9 | 8-7 | 10-5 | 12-1 | |
| Hem-fir | SS | 6-10 | 10-9 | 14-2 | 18-0 | 21-11 | 6-10 | 10-9 | 13-11 | 17-0 | 19-9 | |
| Hem-fir | #1 | 6-8 | 10-3 | 13-0 | 15-11 | 18-5 | 6-3 | 9-2 | 11-8 | 14-3 | 16-6 | |
| Hem-fir | #2 | 6-4 | 9-7 | 12-2 | 14-10 | 17-3 | 5-10 | 8-7 | 10-10 | 13-3 | 15-5 | |
| Hem-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-6 | 6-7 | 8-4 | 10-2 | 11-10 | |
| Southern pine | SS | 7-1 | 11-2 | 14-8 | 18-9 | 22-10 | 7-1 | 11-2 | 14-8 | 17-11 | 21-2 | |
| Southern pine | #1 | 6-10 | 10-7 | 13-5 | 15-9 | 18-8 | 6-4 | 9-6 | 12-0 | 14-1 | 16-8 | |
| Southern pine | #2 | 6-1 | 9-2 | 11-7 | 13-9 | 16-2 | 5-5 | 8-2 | 10-4 | 12-3 | 14-6 | |
| Southern pine | #3 | 4-8 | 6-11 | 8-9 | 10-7 | 12-6 | 4-2 | 6-2 | 7-10 | 9-6 | 11-2 | |
| Spruce-pine-fir | SS | 6-8 | 10-6 | 13-10 | 17-8 | 20-11 | 6-8 | 10-5 | 13-2 | 16-1 | 18-8 | |
| Spruce-pine-fir | #1 | 6-6 | 9-9 | 12-4 | 15-1 | 17-6 | 5-11 | 8-8 | 11-0 | 13-6 | 15-7 | |
| Spruce-pine-fir | #2 | 6-6 | 9-9 | 12-4 | 15-1 | 17-6 | 5-11 | 8-8 | 11-0 | 13-6 | 15-7 | |
| Spruce-pine-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-6 | 6-7 | 8-4 | 10-2 | 11-10 | |
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:
HC/HR Rafter Span Adjustment Factor 1/3 0.67 1/4 0.76 1/5 0.83 1/6 0.90 1/7.5 or less 1.00 where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
- Span exceeds 26 feet in length.
RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load=50 psf, ceiling attached to rafters, L/Δ = 240)
| RAFTER SPACING (inches) | SPECIES AND GRADE | DEAD LOAD = 10 psf | DEAD LOAD = 20 psf | |||||||||
| 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | |||
| Maximum rafter spansa | ||||||||||||
| (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | |||
| 12 | Douglas fir-larch | SS | 7-8 | 12-1 | 15-11 | 20-3 | 24-8 | 7-8 | 12-1 | 15-11 | 20-3 | 24-5 |
| Douglas fir-larch | #1 | 7-5 | 11-7 | 15-3 | 18-7 | 21-7 | 7-5 | 11-2 | 14-1 | 17-3 | 20-0 | |
| Douglas fir-larch | #2 | 7-3 | 11-5 | 14-5 | 17-8 | 20-5 | 7-3 | 10-7 | 13-4 | 16-4 | 18-11 | |
| Douglas fir-larch | #3 | 6-0 | 8-9 | 11-0 | 13-6 | 15-7 | 5-6 | 8-1 | 10-3 | 12-6 | 14-6 | |
| Hem-fir | SS | 7-3 | 11-5 | 15-0 | 19-2 | 23-4 | 7-3 | 11-5 | 15-0 | 19-2 | 23-4 | |
| Hem-fir | #1 | 7-1 | 11-2 | 14-8 | 18-4 | 21-3 | 7-1 | 11-0 | 13-11 | 17-0 | 19-9 | |
| Hem-fir | #2 | 6-9 | 10-8 | 14-0 | 17-2 | 19-11 | 6-9 | 10-3 | 13-0 | 15-10 | 18-5 | |
| Hem-fir | #3 | 5-10 | 8-6 | 10-9 | 13-2 | 15-3 | 5-5 | 7-10 | 10-0 | 12-2 | 14-1 | |
| Southern pine | SS | 7-6 | 11-10 | 15-7 | 19-11 | 24-3 | 7-6 | 11-10 | 15-7 | 19-11 | 24-3 | |
| Southern pine | #1 | 7-3 | 11-5 | 15-0 | 18-2 | 21-7 | 7-3 | 11-4 | 14-5 | 16-10 | 20-0 | |
| Southern pine | #2 | 6-11 | 10-6 | 13-4 | 15-10 | 18-8 | 6-6 | 9-9 | 12-4 | 14-8 | 17-3 | |
| Southern pine | #3 | 5-5 | 8-0 | 10-1 | 12-3 | 14-6 | 5-0 | 7-5 | 9-4 | 11-4 | 13-5 | |
| Spruce-pine-fir | SS | 7-1 | 11-2 | 14-8 | 18-9 | 22-10 | 7-1 | 11-2 | 14-8 | 18-9 | 22-4 | |
| Spruce-pine-fir | #1 | 6-11 | 10-11 | 14-3 | 17-5 | 20-2 | 6-11 | 10-5 | 13-2 | 16-1 | 18-8 | |
| Spruce-pine-fir | #2 | 6-11 | 10-11 | 14-3 | 17-5 | 20-2 | 6-11 | 10-5 | 13-2 | 16-1 | 18-8 | |
| Spruce-pine-fir | #3 | 5-10 | 8-6 | 10-9 | 13-2 | 15-3 | 5-5 | 7-10 | 10-0 | 12-2 | 14-1 | |
| 16 | Douglas fir-larch | SS | 7-0 | 11-0 | 14-5 | 18-5 | 22-5 | 7-0 | 11-0 | 14-5 | 18-3 | 21-2 |
| Douglas fir-larch | #1 | 6-9 | 10-5 | 13-2 | 16-1 | 18-8 | 6-7 | 9-8 | 12-2 | 14-11 | 17-3 | |
| Douglas fir-larch | #2 | 6-7 | 9-10 | 12-6 | 15-3 | 17-9 | 6-3 | 9-2 | 11-7 | 14-2 | 16-5 | |
| Douglas fir-larch | #3 | 5-2 | 7-7 | 9-7 | 11-8 | 13-6 | 4-9 | 7-0 | 8-10 | 10-10 | 12-6 | |
| Hem-fir | SS | 6-7 | 10-4 | 13-8 | 17-5 | 21-2 | 6-7 | 10-4 | 13-8 | 17-5 | 20-5 | |
| Hem-fir | #1 | 6-5 | 10-2 | 13-0 | 15-11 | 18-5 | 6-5 | 9-6 | 12-1 | 14-9 | 17-1 | |
| Hem-fir | #2 | 6-2 | 9-7 | 12-2 | 14-10 | 17-3 | 6-1 | 8-11 | 11-3 | 13-9 | 15-11 | |
| Hem-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-8 | 6-10 | 8-8 | 10-6 | 12-3 | |
| Southern pine | SS | 6-10 | 10-9 | 14-2 | 18-1 | 22-0 | 6-10 | 10-9 | 14-2 | 18-1 | 21-10 | |
| Southern pine | #1 | 6-7 | 10-4 | 13-5 | 15-9 | 18-8 | 6-7 | 9-10 | 12-5 | 14-7 | 17-3 | |
| Southern pine | #2 | 6-1 | 9-2 | 11-7 | 13-9 | 16-2 | 5-8 | 8-5 | 10-9 | 12-9 | 15-0 | |
| Southern pine | #3 | 4-8 | 6-11 | 8-9 | 10-7 | 12-6 | 4-4 | 6-5 | 8-1 | 9-10 | 11-7 | |
| Spruce-pine-fir | SS | 6-5 | 10-2 | 13-4 | 17-0 | 20-9 | 6-5 | 10-2 | 13-4 | 16-8 | 19-4 | |
| Spruce-pine-fir | #1 | 6-4 | 9-9 | 12-4 | 15-1 | 17-6 | 6-2 | 9-0 | 11-5 | 13-11 | 16-2 | |
| Spruce-pine-fir | #2 | 6-4 | 9-9 | 12-4 | 15-1 | 17-6 | 6-2 | 9-0 | 11-5 | 13-11 | 16-2 | |
| Spruce-pine-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-8 | 6-10 | 8-8 | 10-6 | 12-3 | |
| 19.2 | Douglas fir-larch | SS | 6-7 | 10-4 | 13-7 | 17-4 | 20-11 | 6-7 | 10-4 | 13-7 | 16-8 | 19-4 |
| Douglas fir-larch | #1 | 6-4 | 9-6 | 12-0 | 14-8 | 17-1 | 6-0 | 8-10 | 11-2 | 13-7 | 15-9 | |
| Douglas fir-larch | #2 | 6-2 | 9-0 | 11-5 | 13-11 | 16-2 | 5-8 | 8-4 | 10-7 | 12-11 | 15-0 | |
| Douglas fir-larch | #3 | 4-8 | 6-11 | 8-9 | 10-8 | 12-4 | 4-4 | 6-4 | 8-1 | 9-10 | 11-5 | |
| Hem-fir | SS | 6-2 | 9-9 | 12-10 | 16-5 | 19-11 | 6-2 | 9-9 | 12-10 | 16-1 | 18-8 | |
| Hem-fir | #1 | 6-1 | 9-5 | 11-11 | 14-6 | 16-10 | 5-11 | 8-8 | 11-0 | 13-5 | 15-7 | |
| Hem-fir | #2 | 5-9 | 8-9 | 11-1 | 13-7 | 15-9 | 5-7 | 8-1 | 10-3 | 12-7 | 14-7 | |
| Hem-fir | #3 | 4-7 | 6-9 | 8-6 | 10-5 | 12-1 | 4-3 | 6-3 | 7-11 | 9-7 | 11-2 | |
| Southern pine | SS | 6-5 | 10-2 | 13-4 | 17-0 | 20-9 | 6-5 | 10-2 | 13-4 | 16-11 | 20-0 | |
| Southern pine | #1 | 6-2 | 9-8 | 12-3 | 14-4 | 17-1 | 6-0 | 9-0 | 11-4 | 13-4 | 15-9 | |
| Southern pine | #2 | 5-7 | 8-4 | 10-7 | 12-6 | 14-9 | 5-2 | 7-9 | 9-9 | 11-7 | 13-8 | |
| Southern pine | #3 | 4-3 | 6-4 | 8-0 | 9-8 | 11-5 | 4-0 | 5-10 | 7-4 | 8-11 | 10-7 | |
| Spruce-pine-fir | SS | 6-1 | 9-6 | 12-7 | 16-0 | 19-1 | 6-1 | 9-6 | 12-5 | 15-3 | 17-8 | |
| Spruce-pine-fir | #1 | 5-11 | 8-11 | 11-3 | 13-9 | 15-11 | 5-7 | 8-3 | 10-5 | 12-9 | 14-9 | |
| Spruce-pine-fir | #2 | 5-11 | 8-11 | 11-3 | 13-9 | 15-11 | 5-7 | 8-3 | 10-5 | 12-9 | 14-9 | |
| Spruce-pine-fir | #3 | 4-7 | 6-9 | 8-6 | 10-5 | 12-1 | 4-3 | 6-3 | 7-11 | 9-7 | 11-2 | |
| 24 | Douglas fir-larch | SS | 6-1 | 9-7 | 12-7 | 16-1 | 18-8 | 6-1 | 9-7 | 12-2 | 14-11 | 17-3 |
| Douglas fir-larch | #1 | 5-10 | 8-6 | 10-9 | 13-2 | 15-3 | 5-5 | 7-10 | 10-0 | 12-2 | 14-1 | |
| Douglas fir-larch | #2 | 5-6 | 8-1 | 10-3 | 12-6 | 14-6 | 5-1 | 7-6 | 9-5 | 11-7 | 13-5 | |
| Douglas fir-larch | #3 | 4-3 | 6-2 | 7-10 | 9-6 | 11-1 | 3-11 | 5-8 | 7-3 | 8-10 | 10-3 | |
| Hem-fir | SS | 5-9 | 9-1 | 11-11 | 15-2 | 18-0 | 5-9 | 9-1 | 11-9 | 14-5 | 15-11 | |
| Hem-fir | #1 | 5-8 | 8-5 | 10-8 | 13-0 | 15-1 | 5-4 | 7-9 | 9-10 | 12-0 | 13-11 | |
| Hem-fir | #2 | 5-4 | 7-10 | 9-11 | 12-1 | 14-1 | 4-11 | 7-3 | 9-2 | 11-3 | 13-0 | |
| Hem-fir | #3 | 4-1 | 6-0 | 7-7 | 9-4 | 10-9 | 3-10 | 5-7 | 7-1 | 8-7 | 10-0 | |
| Southern pine | SS | 6-0 | 9-5 | 12-5 | 15-10 | 19-3 | 6-0 | 9-5 | 12-5 | 15-2 | 17-10 | |
| Southern pine | #1 | 5-9 | 8-8 | 11-0 | 12-10 | 15-3 | 5-5 | 8-0 | 10-2 | 11-11 | 14-1 | |
| Southern pine | #2 | 5-0 | 7-5 | 9-5 | 11-3 | 13-2 | 4-7 | 6-11 | 8-9 | 10-5 | 12-3 | |
| Southern pine | #3 | 3-10 | 5-8 | 7-1 | 8-8 | 10-3 | 3-6 | 5-3 | 6-7 | 8-0 | 9-6 | |
| Spruce-pine-fir | SS | 5-8 | 8-10 | 11-8 | 14-8 | 17-1 | 5-8 | 8-10 | 11-2 | 13-7 | 15-9 | |
| Spruce-pine-fir | #1 | 5-5 | 7-11 | 10-1 | 12-4 | 14-3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | |
| Spruce-pine-fir | #2 | 5-5 | 7-11 | 10-1 | 12-4 | 14-3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | |
| Spruce-pine-fir | #3 | 4-1 | 6-0 | 7-7 | 9-4 | 10-9 | 3-10 | 5-7 | 7-1 | 8-7 | 10-0 | |
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:
Hc/HR Rafter Span Adjustment Factor 1/3 0.67 1/4 0.76 1/5 0.83 1/6 0.90 1/7.5 or less 1.00 where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
RAFTER SPANS FOR 70 PSF GROUND SNOW LOAD (Ceiling not attached to rafters, L/Δ = 180)
| RAFTER SPACING (inches) | SPECIES AND GRADE | DEAD LOAD = 10 psf | DEAD LOAD = 20 psf | |||||||||
| 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | |||
| Maximum Rafter Spansa | ||||||||||||
| (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | (feet-inches) | |||
| 12 | Douglas fir-larch | SS | 7-7 | 11-10 | 15-8 | 19-9 | 22-10 | 7-7 | 11-10 | 15-3 | 18-7 | 21-7 |
| Douglas fir-larch | #1 | 7-1 | 10-5 | 13-2 | 16-1 | 18-8 | 6-8 | 9-10 | 12-5 | 15-2 | 17-7 | |
| Douglas fir-larch | #2 | 6-9 | 9-10 | 12-6 | 15-3 | 17-9 | 6-4 | 9-4 | 11-9 | 14-5 | 16-8 | |
| Douglas fir-larch | #3 | 5-2 | 7-7 | 9-7 | 11-8 | 13-6 | 4-10 | 7-1 | 9-0 | 11-0 | 12-9 | |
| Hem-fir | SS | 7-2 | 11-3 | 14-9 | 18-10 | 22-1 | 7-2 | 11-3 | 14-8 | 18-0 | 20-10 | |
| Hem-fir | #1 | 7-0 | 10-3 | 13-0 | 15-11 | 18-5 | 6-7 | 9-8 | 12-3 | 15-0 | 17-5 | |
| Hem-fir | #2 | 6-7 | 9-7 | 12-2 | 14-10 | 17-3 | 6-2 | 9-1 | 11-5 | 14-0 | 16-3 | |
| Hem-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-9 | 6-11 | 8-9 | 10-9 | 12-5 | |
| Southern pine | SS | 7-5 | 11-8 | 15-4 | 19-7 | 23-7 | 7-5 | 11-8 | 15-4 | 18-10 | 22-3 | |
| Southern pine | #1 | 7-1 | 10-7 | 13-5 | 15-9 | 18-8 | 6-9 | 10-0 | 12-8 | 14-10 | 17-7 | |
| Southern pine | #2 | 6-1 | 9-2 | 11-7 | 13-9 | 16-2 | 5-9 | 8-7 | 10-11 | 12-11 | 15-3 | |
| Southern pine | #3 | 4-8 | 6-11 | 8-9 | 10-7 | 12-6 | 4-5 | 6-6 | 8-3 | 10-0 | 11-10 | |
| Spruce-pine-fir | SS | 7-0 | 11-0 | 14-6 | 18-0 | 20-11 | 7-0 | 11-0 | 13-11 | 17-0 | 19-8 | |
| Spruce-pine-fir | #1 | 6-8 | 9-9 | 12-4 | 15-1 | 17-6 | 6-3 | 9-2 | 11-8 | 14-2 | 16-6 | |
| Spruce-pine-fir | #2 | 6-8 | 9-9 | 12-4 | 15-1 | 17-6 | 6-3 | 9-2 | 11-8 | 14-2 | 16-6 | |
| Spruce-pine-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-9 | 6-11 | 8-9 | 10-9 | 12-5 | |
| 16 | Douglas fir-larch | SS | 6-10 | 10-9 | 14-0 | 17-1 | 19-10 | 6-10 | 10-5 | 13-2 | 16-1 | 18-8 |
| Douglas fir-larch | #1 | 6-2 | 9-0 | 11-5 | 13-11 | 16-2 | 5-10 | 8-6 | 10-9 | 13-2 | 15-3 | |
| Douglas fir-larch | #2 | 5-10 | 8-7 | 10-10 | 13-3 | 15-4 | 5-6 | 8-1 | 10-3 | 12-6 | 14-6 | |
| Douglas fir-larch | #3 | 4-6 | 6-6 | 8-3 | 10-1 | 11-9 | 4-3 | 6-2 | 7-10 | 9-6 | 11-1 | |
| Hem-fir | SS | 6-6 | 10-2 | 13-5 | 16-6 | 19-2 | 6-6 | 10-1 | 12-9 | 15-7 | 18-0 | |
| Hem-fir | #1 | 6-1 | 8-11 | 11-3 | 13-9 | 16-0 | 5-9 | 8-5 | 10-8 | 13-0 | 15-1 | |
| Hem-fir | #2 | 5-8 | 8-4 | 10-6 | 12-10 | 14-11 | 5-4 | 7-10 | 9-11 | 12-1 | 14-1 | |
| Hem-fir | #3 | 4-4 | 6-4 | 8-1 | 9-10 | 11-5 | 4-1 | 6-0 | 7-7 | 9-4 | 10-9 | |
| Southern pine | SS | 6-9 | 10-7 | 14-0 | 17-4 | 20-5 | 6-9 | 10-7 | 13-9 | 16-4 | 19-3 | |
| Southern pine | #1 | 6-2 | 9-2 | 11-8 | 13-8 | 16-2 | 5-10 | 8-8 | 11-0 | 12-10 | 15-3 | |
| Southern pine | #2 | 5-3 | 7-11 | 10-0 | 11-11 | 14-0 | 5-0 | 7-5 | 9-5 | 11-3 | 13-2 | |
| Southern pine | #3 | 4-1 | 6-0 | 7-7 | 9-2 | 10-10 | 3-10 | 5-8 | 7-1 | 8-8 | 10-3 | |
| Spruce-pine-fir | SS | 6-4 | 10-0 | 12-9 | 15-7 | 18-1 | 6-4 | 9-6 | 12-0 | 14-8 | 17-1 | |
| Spruce-pine-fir | #1 | 5-9 | 8-5 | 10-8 | 13-1 | 15-2 | 5-5 | 7-11 | 10-1 | 12-4 | 14-3 | |
| Spruce-pine-fir | #2 | 5-9 | 8-5 | 10-8 | 13-1 | 15-2 | 5-5 | 7-11 | 10-1 | 12-4 | 14-3 | |
| Spruce-pine-fir | #3 | 4-4 | 6-4 | 8-1 | 9-10 | 11-5 | 4-1 | 6-0 | 7-7 | 9-4 | 10-9 | |
| 19.2 | Douglas fir-larch | SS | 6-6 | 10-1 | 12-9 | 15-7 | 18-1 | 6-6 | 9-6 | 12-0 | 14-8 | 17-1 |
| Douglas fir-larch | #1 | 5-7 | 8-3 | 10-5 | 12-9 | 14-9 | 5-4 | 7-9 | 9-10 | 12-0 | 13-11 | |
| Douglas fir-larch | #2 | 5-4 | 7-10 | 9-11 | 12-1 | 14-0 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | |
| Douglas fir-larch | #3 | 4-1 | 6-0 | 7-7 | 9-3 | 10-8 | 3-10 | 5-7 | 7-1 | 8-8 | 10-1 | |
| Hem-fir | SS | 6-1 | 9-7 | 12-4 | 15-1 | 17-4 | 6-1 | 9-2 | 11-8 | 14-2 | 15-5 | |
| Hem-fir | #1 | 5-7 | 8-2 | 10-3 | 12-7 | 14-7 | 5-3 | 7-8 | 9-8 | 11-10 | 13-9 | |
| Hem-fir | #2 | 5-2 | 7-7 | 9-7 | 11-9 | 13-7 | 4-11 | 7-2 | 9-1 | 11-1 | 12-10 | |
| Hem-fir | #3 | 4-0 | 5-10 | 7-4 | 9-0 | 10-5 | 3-9 | 5-6 | 6-11 | 8-6 | 9-10 | |
| Southern pine | SS | 6-4 | 10-0 | 13-2 | 15-10 | 18-8 | 6-4 | 9-10 | 12-6 | 14-11 | 17-7 | |
| Southern pine | #1 | 5-8 | 8-5 | 10-8 | 12-5 | 14-9 | 5-4 | 7-11 | 10-0 | 11-9 | 13-11 | |
| Southern pine | #2 | 4-10 | 7-3 | 9-2 | 10-10 | 12-9 | 4-6 | 6-10 | 8-8 | 10-3 | 12-1 | |
| Southern pine | #3 | 3-8 | 5-6 | 6-11 | 8-4 | 9-11 | 3-6 | 5-2 | 6-6 | 7-11 | 9-4 | |
| Spruce-pine-fir | SS | 6-0 | 9-2 | 11-8 | 14-3 | 16-6 | 5-11 | 8-8 | 11-0 | 13-5 | 15-7 | |
| Spruce-pine-fir | #1 | 5-3 | 7-8 | 9-9 | 11-11 | 13-10 | 5-0 | 7-3 | 9-2 | 11-3 | 13-0 | |
| Spruce-pine-fir | #2 | 5-3 | 7-8 | 9-9 | 11-11 | 13-10 | 5-0 | 7-3 | 9-2 | 11-3 | 13-0 | |
| Spruce-pine-fir | #3 | 4-0 | 5-10 | 7-4 | 9-0 | 10-5 | 3-9 | 5-6 | 6-11 | 8-6 | 9-10 | |
| 24 | Douglas fir-larch | SS | 6-0 | 9-0 | 11-5 | 13-11 | 16-2 | 5-10 | 8-6 | 10-9 | 13-2 | 15-3 |
| Douglas fir-larch | #1 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-9 | 6-11 | 8-9 | 10-9 | 12-5 | |
| Douglas fir-larch | #2 | 4-9 | 7-0 | 8-10 | 10-10 | 12-6 | 4-6 | 6-7 | 8-4 | 10-2 | 11-10 | |
| Douglas fir-larch | #3 | 3-8 | 5-4 | 6-9 | 8-3 | 9-7 | 3-5 | 5-0 | 6-4 | 7-9 | 9-10 | |
| Hem-fir | SS | 5-8 | 8-8 | 11-0 | 13-6 | 13-11 | 5-7 | 8-3 | 10-5 | 12-4 | 12-4 | |
| Hem-fir | #1 | 5-0 | 7-3 | 9-2 | 11-3 | 13-0 | 4-8 | 6-10 | 8-8 | 10-7 | 12-4 | |
| Hem-fir | #2 | 4-8 | 6-9 | 8-7 | 10-6 | 12-2 | 4-4 | 6-5 | 8-1 | 9-11 | 11-6 | |
| Hem-fir | #3 | 3-7 | 5-2 | 6-7 | 8-1 | 9-4 | 3-4 | 4-11 | 6-3 | 7-7 | 8-10 | |
| Southern pine | SS | 5-11 | 9-3 | 11-11 | 14-2 | 16-8 | 5-11 | 8-10 | 11-2 | 13-4 | 15-9 | |
| Southern pine | #1 | 5-0 | 7-6 | 9-6 | 11-1 | 13-2 | 4-9 | 7-1 | 9-0 | 10-6 | 12-5 | |
| Southern pine | #2 | 4-4 | 6-5 | 8-2 | 9-9 | 11-5 | 4-1 | 6-1 | 7-9 | 9-2 | 10-9 | |
| Southern pine | #3 | 3-4 | 4-11 | 6-2 | 7-6 | 8-10 | 3-1 | 4-7 | 5-10 | 7-1 | 8-4 | |
| Spruce-pine-fir | SS | 5-6 | 8-3 | 10-5 | 12-9 | 14-9 | 5-4 | 7-9 | 9-10 | 12-0 | 12-11 | |
| Spruce-pine-fir | #1 | 4-8 | 6-11 | 8-9 | 10-8 | 12-4 | 4-5 | 6-6 | 8-3 | 10-0 | 11-8 | |
| Spruce-pine-fir | #2 | 4-8 | 6-11 | 8-9 | 10-8 | 12-4 | 4-5 | 6-6 | 8-3 | 10-0 | 11-8 | |
| Spruce-pine-fir | #3 | 3-7 | 5-2 | 6-7 | 8-1 | 9-4 | 3-4 | 4-11 | 6-3 | 7-7 | 8-10 | |
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:
HC/HR Rafter Span Adjustment Factor 1/3 0.67 1/4 0.76 1/5 0.83 1/6 0.90 1/7.5 or less 1.00 where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
RAFTER SPANS FOR 70 PSF GROUND SNOW LOAD (Ceiling attached to rafters, L/Δ = 240)
| RAFTER SPACING (inches) | SPECIES AND GRADE | DEAD LOAD = 10 psf | DEAD LOAD = 20 psf | |||||||||
| 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | 2 × 4 | 2 × 6 | 2 × 8 | 2 × 10 | 2 × 12 | |||
| Maximum rafter spansa | ||||||||||||
| (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | (feet - inches) | |||
| 12 | Douglas fir-larch | SS | 6-10 | 10-9 | 14-3 | 18-2 | 22-1 | 6-10 | 10-9 | 14-3 | 18-2 | 21-7 |
| Douglas fir-larch | #1 | 6-7 | 10-5 | 13-2 | 16-1 | 18-8 | 6-7 | 9-10 | 12-5 | 15-2 | 17-7 | |
| Douglas fir-larch | #2 | 6-6 | 9-10 | 12-6 | 15-3 | 17-9 | 6-4 | 9-4 | 11-9 | 14-5 | 16-8 | |
| Douglas fir-larch | #3 | 5-2 | 7-7 | 9-7 | 11-8 | 13-6 | 4-10 | 7-1 | 9-0 | 11-0 | 12-9 | |
| Hem-fir | SS | 6-6 | 10-2 | 13-5 | 17-2 | 20-10 | 6-6 | 10-2 | 13-5 | 17-2 | 20-10 | |
| Hem-fir | #1 | 6-4 | 10-0 | 13-0 | 15-11 | 18-5 | 6-4 | 9-8 | 12-3 | 15-0 | 17-5 | |
| Hem-fir | #2 | 6-1 | 9-6 | 12-2 | 14-10 | 17-3 | 6-1 | 9-1 | 11-5 | 14-0 | 16-3 | |
| Hem-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-9 | 6-11 | 8-9 | 10-9 | 12-5 | |
| Southern pine | SS | 6-9 | 10-7 | 14-0 | 17-10 | 21-8 | 6-9 | 10-7 | 14-0 | 17-10 | 21-8 | |
| Southern pine | #1 | 6-6 | 10-2 | 13-5 | 15-9 | 18-8 | 6-6 | 10-0 | 12-8 | 14-10 | 17-7 | |
| Southern pine | #2 | 6-1 | 9-2 | 11-7 | 13-9 | 16-2 | 5-9 | 8-7 | 10-11 | 12-11 | 15-3 | |
| Southern pine | #3 | 4-8 | 6-11 | 8-9 | 10-7 | 12-6 | 4-5 | 6-6 | 8-3 | 10-0 | 11-10 | |
| Spruce-pine-fir | SS | 6-4 | 10-0 | 13-2 | 16-9 | 20-5 | 6-4 | 10-0 | 13-2 | 16-9 | 19-8 | |
| Spruce-pine-fir | #1 | 6-2 | 9-9 | 12-4 | 15-1 | 17-6 | 6-2 | 9-2 | 11-8 | 14-2 | 16-6 | |
| Spruce-pine-fir | #2 | 6-2 | 9-9 | 12-4 | 15-1 | 17-6 | 6-2 | 9-2 | 11-8 | 14-2 | 16-6 | |
| Spruce-pine-fir | #3 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-9 | 6-11 | 8-9 | 10-9 | 12-5 | |
| 16 | Douglas fir-larch | SS | 6-3 | 9-10 | 12-11 | 16-6 | 19-10 | 6-3 | 9-10 | 12-11 | 16-1 | 18-8 |
| Douglas fir-larch | #1 | 6-0 | 9-0 | 11-5 | 13-11 | 16-2 | 5-10 | 8-6 | 10-9 | 13-2 | 15-3 | |
| Douglas fir-larch | #2 | 5-10 | 8-7 | 10-10 | 13-3 | 15-4 | 5-6 | 8-1 | 10-3 | 12-6 | 14-6 | |
| Douglas fir-larch | #3 | 4-6 | 6-6 | 8-3 | 10-1 | 11-9 | 4-3 | 6-2 | 7-10 | 9-6 | 11-1 | |
| Hem-fir | SS | 5-11 | 9-3 | 12-2 | 15-7 | 18-11 | 5-11 | 9-3 | 12-2 | 15-7 | 18-0 | |
| Hem-fir | #1 | 5-9 | 8-11 | 11-3 | 13-9 | 16-0 | 5-9 | 8-5 | 10-8 | 13-0 | 15-1 | |
| Hem-fir | #2 | 5-6 | 8-4 | 10-6 | 12-10 | 14-11 | 5-4 | 7-10 | 9-11 | 12-1 | 14-1 | |
| Hem-fir | #3 | 4-4 | 6-4 | 8-1 | 9-10 | 11-5 | 4-1 | 6-0 | 7-7 | 9-4 | 10-9 | |
| Southern pine | SS | 6-1 | 9-7 | 12-8 | 16-2 | 19-8 | 6-1 | 9-7 | 12-8 | 16-2 | 19-3 | |
| Southern pine | #1 | 5-11 | 9-2 | 11-8 | 13-8 | 16-2 | 5-10 | 8-8 | 11-0 | 12-10 | 15-3 | |
| Southern pine | #2 | 5-3 | 7-11 | 10-0 | 11-11 | 14-0 | 5-0 | 7-5 | 9-5 | 11-3 | 13-2 | |
| Southern pine | #3 | 4-1 | 6-0 | 7-7 | 9-2 | 10-10 | 3-10 | 5-8 | 7-1 | 8-8 | 10-3 | |
| Spruce-pine-fir | SS | 5-9 | 9-1 | 11-11 | 15-3 | 18-1 | 5-9 | 9-1 | 11-11 | 14-8 | 17-1 | |
| Spruce-pine-fir | #1 | 5-8 | 8-5 | 10-8 | 13-1 | 15-2 | 5-5 | 7-11 | 10-1 | 12-4 | 14-3 | |
| Spruce-pine-fir | #2 | 5-8 | 8-5 | 10-8 | 13-1 | 15-2 | 5-5 | 7-11 | 10-1 | 12-4 | 14-3 | |
| Spruce-pine-fir | #3 | 4-4 | 6-4 | 8-1 | 9-10 | 11-5 | 4-1 | 6-0 | 7-7 | 9-4 | 10-9 | |
| 19.2 | Douglas fir-larch | SS | 5-10 | 9-3 | 12-2 | 15-6 | 18-1 | 5-10 | 9-3 | 12-0 | 14-8 | 17-1 |
| Douglas fir-larch | #1 | 5-7 | 8-3 | 10-5 | 12-9 | 14-9 | 5-4 | 7-9 | 9-10 | 12-0 | 13-11 | |
| Douglas fir-larch | #2 | 5-4 | 7-10 | 9-11 | 12-1 | 14-0 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | |
| Douglas fir-larch | #3 | 4-1 | 6-0 | 7-7 | 9-3 | 10-8 | 3-10 | 5-7 | 7-1 | 8-8 | 10-1 | |
| Hem-fir | SS | 5-6 | 8-8 | 11-6 | 14-8 | 17-4 | 5-6 | 8-8 | 11-6 | 14-2 | 15-5 | |
| Hem-fir | #1 | 5-5 | 8-2 | 10-3 | 12-7 | 14-7 | 5-3 | 7-8 | 9-8 | 11-10 | 13-9 | |
| Hem-fir | #2 | 5-2 | 7-7 | 9-7 | 11-9 | 13-7 | 4-11 | 7-2 | 9-1 | 11-1 | 12-10 | |
| Hem-fir | #3 | 4-0 | 5-10 | 7-4 | 9-0 | 10-5 | 3-9 | 5-6 | 6-11 | 8-6 | 9-10 | |
| Southern pine | SS | 5-9 | 9-1 | 11-11 | 15-3 | 18-6 | 5-9 | 9-1 | 11-11 | 14-11 | 17-7 | |
| Southern pine | #1 | 5-6 | 8-5 | 10-8 | 12-5 | 14-9 | 5-4 | 7-11 | 10-0 | 11-9 | 13-11 | |
| Southern pine | #2 | 4-10 | 7-3 | 9-2 | 10-10 | 12-9 | 4-6 | 6-10 | 8-8 | 10-3 | 12-1 | |
| Southern pine | #3 | 3-8 | 5-6 | 6-11 | 8-4 | 9-11 | 3-6 | 5-2 | 6-6 | 7-11 | 9-4 | |
| Spruce-pine-fir | SS | 5-5 | 8-6 | 11-3 | 14-3 | 16-6 | 5-5 | 8-6 | 11-0 | 13-5 | 15-7 | |
| Spruce-pine-fir | #1 | 5-3 | 7-8 | 9-9 | 11-11 | 13-10 | 5-0 | 7-3 | 9-2 | 11-3 | 13-0 | |
| Spruce-pine-fir | #2 | 5-3 | 7-8 | 9-9 | 11-11 | 13-10 | 5-0 | 7-3 | 9-2 | 11-3 | 13-0 | |
| Spruce-pine-fir | #3 | 4-0 | 5-10 | 7-4 | 9-0 | 10-5 | 3-9 | 5-6 | 6-11 | 8-6 | 9-10 | |
| 24 | Douglas fir-larch | SS | 5-5 | 8-7 | 11-3 | 13-11 | 16-2 | 5-5 | 8-6 | 10-9 | 13-2 | 15-3 |
| Douglas fir-larch | #1 | 5-0 | 7-4 | 9-4 | 11-5 | 13-2 | 4-9 | 6-11 | 8-9 | 10-9 | 12-5 | |
| Douglas fir-larch | #2 | 4-9 | 7-0 | 8-10 | 10-10 | 12-6 | 4-6 | 6-7 | 8-4 | 10-2 | 11-10 | |
| Douglas fir-larch | #3 | 3-8 | 5-4 | 6-9 | 8-3 | 9-7 | 3-5 | 5-0 | 6-4 | 7-9 | 9-0 | |
| Hem-fir | SS | 5-2 | 8-1 | 10-8 | 13-6 | 13-11 | 5-2 | 8-1 | 10-5 | 12-4 | 12-4 | |
| Hem-fir | #1 | 5-0 | 7-3 | 9-2 | 11-3 | 13-0 | 4-8 | 6-10 | 8-8 | 10-7 | 12-4 | |
| Hem-fir | #2 | 4-8 | 6-9 | 8-7 | 10-6 | 12-2 | 4-4 | 6-5 | 8-1 | 9-11 | 11-6 | |
| Hem-fir | #3 | 3-7 | 5-2 | 6-7 | 8-1 | 9-4 | 3-4 | 4-11 | 6-3 | 7-7 | 8-10 | |
| Southern pine | SS | 5-4 | 8-5 | 11-1 | 14-2 | 16-8 | 5-4 | 8-5 | 11-1 | 13-4 | 15-9 | |
| Southern pine | #1 | 5-0 | 7-6 | 9-6 | 11-1 | 13-2 | 4-9 | 7-1 | 9-0 | 10-6 | 12-5 | |
| Southern pine | #2 | 4-4 | 6-5 | 8-2 | 9-9 | 11-5 | 4-1 | 6-1 | 7-9 | 9-2 | 10-9 | |
| Southern pine | #3 | 3-4 | 4-11 | 6-2 | 7-6 | 8-10 | 3-1 | 4-7 | 5-10 | 7-1 | 8-4 | |
| Spruce-pine-fir | SS | 5-0 | 7-11 | 10-5 | 12-9 | 14-9 | 5-0 | 7-9 | 9-10 | 12-0 | 12-11 | |
| Spruce-pine-fir | #1 | 4-8 | 6-11 | 8-9 | 10-8 | 12-4 | 4-5 | 6-6 | 8-3 | 10-0 | 11-8 | |
| Spruce-pine-fir | #2 | 4-8 | 6-11 | 8-9 | 10-8 | 12-4 | 4-5 | 6-6 | 8-3 | 10-0 | 11-8 | |
| Spruce-pine-fir | #3 | 3-7 | 5-2 | 6-7 | 8-1 | 9-4 | 3-4 | 4-11 | 6-3 | 7-7 | 8-10 | |
Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the bearing walls, such as rafter ties, is provided at that location. When ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the factors given below:
HC/HR Rafter Span Adjustment Factor 1/3 0.67 1/4 0.76 1/5 0.83 1/6 0.90 1/7.5 or less 1.00 where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
TABLE R802.5.1(9)91.5.802.5.1(9)
RAFTER/CEILING JOIST HEEL JOINT CONNECTIONSa, b, c, d, e, f, h
| RAFTER SLOPE | RAFTER SPACING (inches) | GROUND SNOW LOAD (psf) | |||||||||||||||
| 20g | 30 | 50 | 70 | ||||||||||||||
| Roof span (feet) | |||||||||||||||||
| 12 | 20 | 28 | 36 | 12 | 20 | 28 | 36 | 12 | 20 | 28 | 36 | 12 | 20 | 28 | 36 | ||
| Required number of 16d common nailsa, b per heel joint splicesc, d, e, f | |||||||||||||||||
| 3:12 | 12 | 4 | 6 | 8 | 10 | 4 | 6 | 8 | 11 | 5 | 8 | 12 | 15 | 6 | 11 | 15 | 20 |
| 16 | 5 | 8 | 10 | 13 | 5 | 8 | 11 | 14 | 6 | 11 | 15 | 20 | 8 | 14 | 20 | 26 | |
| 24 | 7 | 11 | 15 | 19 | 7 | 11 | 16 | 21 | 9 | 16 | 23 | 30 | 12 | 21 | 30 | 39 | |
| 4:12 | 12 | 3 | 5 | 6 | 8 | 3 | 5 | 6 | 8 | 4 | 6 | 9 | 11 | 5 | 8 | 12 | 15 |
| 16 | 4 | 6 | 8 | 10 | 4 | 6 | 8 | 11 | 5 | 8 | 12 | 15 | 6 | 11 | 15 | 20 | |
| 24 | 5 | 8 | 12 | 15 | 5 | 9 | 12 | 16 | 7 | 12 | 17 | 22 | 9 | 16 | 23 | 29 | |
| 5:12 | 12 | 3 | 4 | 5 | 6 | 3 | 4 | 5 | 7 | 3 | 5 | 7 | 9 | 4 | 7 | 9 | 12 |
| 16 | 3 | 5 | 6 | 8 | 3 | 5 | 7 | 9 | 4 | 7 | 9 | 12 | 5 | 9 | 12 | 16 | |
| 24 | 4 | 7 | 9 | 12 | 4 | 7 | 10 | 13 | 6 | 10 | 14 | 18 | 7 | 13 | 18 | 23 | |
| 7:12 | 12 | 3 | 4 | 4 | 5 | 3 | 3 | 4 | 5 | 3 | 4 | 5 | 7 | 3 | 5 | 7 | 9 |
| 16 | 3 | 4 | 5 | 6 | 3 | 4 | 5 | 6 | 3 | 5 | 7 | 9 | 4 | 6 | 9 | 11 | |
| 24 | 3 | 5 | 7 | 9 | 3 | 5 | 7 | 9 | 4 | 7 | 10 | 13 | 5 | 9 | 13 | 17 | |
| 9:12 | 12 | 3 | 3 | 4 | 4 | 3 | 3 | 3 | 4 | 3 | 3 | 4 | 5 | 3 | 4 | 5 | 7 |
| 16 | 3 | 4 | 4 | 5 | 3 | 3 | 4 | 5 | 3 | 4 | 5 | 7 | 3 | 5 | 7 | 9 | |
| 24 | 3 | 4 | 6 | 7 | 3 | 4 | 6 | 7 | 3 | 6 | 8 | 10 | 4 | 7 | 10 | 13 | |
| 12:12 | 12 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 3 | 4 | 3 | 3 | 4 | 5 |
| 16 | 3 | 3 | 4 | 4 | 3 | 3 | 3 | 4 | 3 | 3 | 4 | 5 | 3 | 4 | 5 | 7 | |
| 24 | 3 | 4 | 4 | 5 | 3 | 3 | 4 | 6 | 3 | 4 | 6 | 8 | 3 | 6 | 8 | 10 | |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
- 40d box nails shall be permitted to be substituted for 16d common nails.
- Nailing requirements shall be permitted to be reduced 25 percent if nails are clinched.
- Heel joint connections are not required where when the ridge is supported by a load-bearing wall, header or ridge beam.
- Where intermediate When immediate support of the rafter is provided by vertical struts or purlins to a load-bearing wall, the tabulated heel joint connection requirements shall be permitted to be reduced proportionally to the reduction in span.
- Equivalent nailing patterns are required for ceiling joists to ceiling joist lap splices.
- Where When rafter ties are substituted for ceiling joists, the heel joint connection requirement shall be taken as the tabulated heel joint connection requirement for two-thirds of the actual rafter slope.
- Applies to roof live load of 20 psf or less.
Tabulated heel joint connection requirements assume that ceiling joists or rafter ties are located at the bottom of the attic space. WhereWhen ceiling joists or rafter ties are located higher in the attic, heel joint connection requirements shall be increased by the following factors:
HC/HR Heel Joint Connection Adjustment Factor 1/3 1.5 1/4 1.33 1/5 1.25 1/6 1.2 1/10 or less 1.11 where:
HC = Height of ceiling joists or rafter ties measured vertically above the top of the rafter support walls.
HR = Height of the roof ridge measured vertically above the top of the rafter support walls.
- Edge distances, end distances and spacing for nails shall be sufficient to prevent splitting of the wood.
For SI: 1 inch = 25.4 mm, 1 foot = 305 mm, 1 degree = 0.018 rad.
Note: Where ceiling joists run perpendicular to the rafter, rafter ties shall be installed in accordance with Section R802.3.1.
HC = Height of ceiling joists or rafter ties measured vertically above the top of rafter support walls.
HR = Height of roof ridge measured vertically above the top of the rafter support walls.
BRACED RAFTER CONSTRUCTION
Related Code Sections
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