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Table 34 Maximum spans for ceiling joists – attic not accessible by a stairway1, 2 Rafter Tied to Every Joist
Rafter Tied to Joist Every 1.2 m (3 ft., 11 in.)
Building Width up to
Building Width up to
8m (26 ft., 3 in.)
9.8 m (32 ft., 2 in.)
8m (26 ft., 3 in.)
9.8 m (32 ft., 2 in.)
Roof Snow Load, kPa (psf)3
Roof Slope
Rafter Spacing, mm (in.)
1 (20) or less
1.5 (30)
2.0 (40) or more
1 (20) or less
1.5 (30)
2.0 (40) or more
1 (20) or less
1.5 (30)
2.0 (40) or more
1 (20) or less
1.5 (30)
2.0 (40) or more
1:3
400 (16)
4
5
6
5
7
8
11
–
–
–
–
–
600 (24)
6
8
9
8
–
–
11
–
–
–
–
–
400 (16)
4
4
5
5
6
7
7
10
–
9
–
–
600 (24)
5
7
8
7
9
11
7
10
–
–
–
–
400 (16)
4
4
4
4
4
5
6
8
9
8
–
–
600 (24)
4
5
6
5
7
8
6
8
9
8
–
–
400 (16)
4
4
4
4
4
4
5
7
8
7
9
11
600 (24)
4
4
5
5
6
7
5
7
8
7
9
11
400 (16)
4
4
4
4
4
4
4
5
6
5
6
7
600 (24)
4
4
4
4
4
5
4
5
6
5
6
7
400 (16)
4
4
4
4
4
4
4
4
4
4
4
5
600 (24)
4
4
4
4
4
4
4
4
4
4
4
5
1:2.4
1:2
1:1.71
1:1.33
1:1
Notes to Table 34 1. Nails not less than 79 mm (31⁄8 in.). 2. Ceiling joists must be fastened together with at least one more nail per joist splice than required for the rafter-to-joist connection. 3. To determine the specified snow load in your location, contact your municipal building department.