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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

SpeciesDimension20 lb per sq ft snow load30 lb per sq ft snow load
Rafter SpacingRafter Spacing
12"16"24"12"16"24"
Hemlock
Fir
2x410'-8"9'-9"9'-6"9'-4"8'-6"7'-5"
2x616'-10"15'-4"13'-4"14'-8"13'-4"11'-5"
2x822'-2"20'-1"16'-6"19'-4"17'-1"13'-11"
2x1028'-0"24'-7"20'-2"24'-12"20'-10"17'-0"
2x1233'-2"28'-8"23'-5"28'-0"24'-3"19'-9"
Spruce
Pine
Fir
2x410'-2"9'-3"8'-1"8'-11"8'-1"7'-1"
2x616'-1"14'-7"12'-9"14'-1"12'-9"11'-1"
2x821'-1"19'-2"16'-9"18'-5"16'-9"14'-5"
2x1026'-11"24'-6" 20'-11"23'-6"21'-4"17'-8"
2x1232'-9"29'-8"24'-3"28'-8"25'-1"20'-6"

SpeciesDimension40 lb per sq ft snow load50 lb per sq ft snow load
Rafter SpacingRafter Spacing
12"16"24"12"16"24"
Hemlock
Fir
2x48'-6"7'-9"13'-9"7'-10"7'-2"6'-3"
2x613'-4"12'-2"10'-1"12'-5"11'-2"9'-1"
2x817'-5"15'-1"12'-3"15'-9"13'-7"11'-11"
2x1021'-3"18'-5"15'-0"19'-3"16'-8"13'-7"
2x1224'-8"21'-4"17'-6"22'-4"19'-4"15'-9"
Spruce
Pine
Fir
2x48'-1"7'-4"6'-5"7'-6"6'-10"5'-11"
2x612'-9"11'-7"10'-1"11'-10"10'-9"9'-4"
2x816'-9"15'-2"12'-9"15'-6"14'-1"11'-6"
2x1021'-5"19'-2"15'-7"19'-10"17'-3"14'-1"
2x1225'-7"22'-2"18'-1"23'-2"20'-0"16'-4"

SpeciesDimension60 lb per sq ft snow load
Rafter Spacing
12"16"24"
Hemlock
Fir
2x47'-5"6'-9"5'-11"
2x610'-3"8'-5"
2x814'-6"12'-7"10'-3"
2x1017'-8"15'-4"12'-6"
2x1220'-7"17'-10"14'-6"
Spruce
Pine
Fir
2x47'-1"6'-5"5'-7"
2x611'-2"10'-1"8'-8"
2x814'-7"13'-0"10'-7"
2x1018'-4"15'-10"13'-0"
2x1221'-3"18'-5"15'-0"


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