Tempo:
CHOOSING THE SIZE AND SPACING OF ROOF RAFTERS Problem
Select the smallest dimension rafter that is able to span the roof as follows.
Selection
Conditions
Building is located in Ottawa. Specified roof snow load is 1.72 kPa (36 lbs/sq. ft.).
Roof slope is 1:3.
Rafter span is 4.7 m (15 ft. 6 in.).
Species group and grade specified is SPF No. 2 and better. Shingle roofing to be used.
Lower ends of the rafter are restrained.
Use Table 31 (p. 299). Acceptable rafters include: 38 × 184 mm (2 × 8 in.) at 300 mm (12 in.) on centre. 38 × 235 mm (2 × 10 in.) at 600 mm (24 in.) on centre. Note: The rafters must also be deep enough to accommodate the required level of insulation.
95 Roof rafters
Rafter span = 4.7 m (15 ft. 6 in.)
3 1
Select the smallest dimension rafter that is able to span the roof as follows.
Selection
Conditions
Building is located in Ottawa. Specified roof snow load is 1.72 kPa (36 lbs/sq. ft.).
Roof slope is 1:3.
Rafter span is 4.7 m (15 ft. 6 in.).
Species group and grade specified is SPF No. 2 and better. Shingle roofing to be used.
Lower ends of the rafter are restrained.
Use Table 31 (p. 299). Acceptable rafters include: 38 × 184 mm (2 × 8 in.) at 300 mm (12 in.) on centre. 38 × 235 mm (2 × 10 in.) at 600 mm (24 in.) on centre. Note: The rafters must also be deep enough to accommodate the required level of insulation.
95 Roof rafters
Rafter span = 4.7 m (15 ft. 6 in.)
3 1
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