Tables 3: Span Tables for Rafters
These span tables are taken from the National Building Code of Canada, 1998 BC Edition (current edition) and are for reference only. The final authority in building codes, including rafter spans, lies with the building inspector in your local area. To improve the span of rafters it is recommended to use collar ties or pony walls.
Maximum Spans for Roof Rafters
Span in feet-inches using No. 2 and better
| Species | Dimension | 20 lb per sq ft snow load | 30 lb per sq ft snow load | ||||
|---|---|---|---|---|---|---|---|
| Rafter Spacing | Rafter Spacing | ||||||
| 12" | 16" | 24" | 12" | 16" | 24" | ||
| Hemlock Fir | 2x4 | 10'-8" | 9'-9" | 9'-6" | 9'-4" | 8'-6" | 7'-5" |
| 2x6 | 16'-10" | 15'-4" | 13'-4" | 14'-8" | 13'-4" | 11'-5" | |
| 2x8 | 22'-2" | 20'-1" | 16'-6" | 19'-4" | 17'-1" | 13'-11" | |
| 2x10 | 28'-0" | 24'-7" | 20'-2" | 24'-12" | 20'-10" | 17'-0" | |
| 2x12 | 33'-2" | 28'-8" | 23'-5" | 28'-0" | 24'-3" | 19'-9" | |
| Spruce Pine Fir | 2x4 | 10'-2" | 9'-3" | 8'-1" | 8'-11" | 8'-1" | 7'-1" |
| 2x6 | 16'-1" | 14'-7" | 12'-9" | 14'-1" | 12'-9" | 11'-1" | |
| 2x8 | 21'-1" | 19'-2" | 16'-9" | 18'-5" | 16'-9" | 14'-5" | |
| 2x10 | 26'-11" | 24'-6" | 20'-11" | 23'-6" | 21'-4" | 17'-8" | |
| 2x12 | 32'-9" | 29'-8" | 24'-3" | 28'-8" | 25'-1" | 20'-6" | |
| Species | Dimension | 40 lb per sq ft snow load | 50 lb per sq ft snow load | ||||
|---|---|---|---|---|---|---|---|
| Rafter Spacing | Rafter Spacing | ||||||
| 12" | 16" | 24" | 12" | 16" | 24" | ||
| Hemlock Fir | 2x4 | 8'-6" | 7'-9" | 13'-9" | 7'-10" | 7'-2" | 6'-3" |
| 2x6 | 13'-4" | 12'-2" | 10'-1" | 12'-5" | 11'-2" | 9'-1" | |
| 2x8 | 17'-5" | 15'-1" | 12'-3" | 15'-9" | 13'-7" | 11'-11" | |
| 2x10 | 21'-3" | 18'-5" | 15'-0" | 19'-3" | 16'-8" | 13'-7" | |
| 2x12 | 24'-8" | 21'-4" | 17'-6" | 22'-4" | 19'-4" | 15'-9" | |
| Spruce Pine Fir | 2x4 | 8'-1" | 7'-4" | 6'-5" | 7'-6" | 6'-10" | 5'-11" |
| 2x6 | 12'-9" | 11'-7" | 10'-1" | 11'-10" | 10'-9" | 9'-4" | |
| 2x8 | 16'-9" | 15'-2" | 12'-9" | 15'-6" | 14'-1" | 11'-6" | |
| 2x10 | 21'-5" | 19'-2" | 15'-7" | 19'-10" | 17'-3" | 14'-1" | |
| 2x12 | 25'-7" | 22'-2" | 18'-1" | 23'-2" | 20'-0" | 16'-4" | |
| Species | Dimension | 60 lb per sq ft snow load | ||
|---|---|---|---|---|
| Rafter Spacing | ||||
| 12" | 16" | 24" | ||
| Hemlock Fir | 2x4 | 7'-5" | 6'-9" | 5'-11" |
| 2x6 | 10'-3" | 8'-5" | ||
| 2x8 | 14'-6" | 12'-7" | 10'-3" | |
| 2x10 | 17'-8" | 15'-4" | 12'-6" | |
| 2x12 | 20'-7" | 17'-10" | 14'-6" | |
| Spruce Pine Fir | 2x4 | 7'-1" | 6'-5" | 5'-7" |
| 2x6 | 11'-2" | 10'-1" | 8'-8" | |
| 2x8 | 14'-7" | 13'-0" | 10'-7" | |
| 2x10 | 18'-4" | 15'-10" | 13'-0" | |
| 2x12 | 21'-3" | 18'-5" | 15'-0" | |
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