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Table 30 Maximum spans for roof joists – specified roof snow loads 2.5 and 3.0 kPa (52.2 and 62.7 psf) Maximum Span, m (ft.–in.) Specified Snow Load, kPa (psf)1
Commercial Designation Douglas fir – larch (includes Douglas fir and western larch)
Hem – fir (includes western hemlock and amabilis fir)
2.5 (52.2)
3.0 (62.7)
Joist Spacing, mm (in.)
Joist Spacing, mm (in.)
Joist Size, mm
300
400
600
300
400
600
Grade
in.
12
16
24
12
16
24
No. 1 and No. 2
38 x 89
1.91
1.74
1.52
1.80
1.63
1.43
2x4
6–3
5–8
5–0
5–11
5–4
4–8
38 x 140
3.01
2.73
2.39
2.83
2.57
2.25
2x6
9–10
9–0
7–10
9–3
8–5
7–4
38 x 184
3.95
3.59
3.14
3.72
3.38
2.90
2x8
13–0
11–9
10–3
12–2
11–1
9–6
38 x 235
5.05
4.59
3.84
4.75
4.32
3.55
2 x 10
16–7
15–1
12–7
15–7
14–2
11–8
38 x 286
6.14
5.46
4.46
5.78
5.05
4.12
2 x 12
20–2
17–11
14–8
19–0
16–7
13–6
38 x 89
1.91
1.74
1.52
1.80
1.63
1.43
2x4
6–3
5–8
5–0
5–11
5–4
4–8
38 x 140
3.01
2.73
2.39
2.83
2.57
2.25
2x6
9–10
9–0
7–10
9–3
8–5
7–4
38 x 184
3.95
3.59
3.14
3.72
3.38
2.95
2x8
13–0
11–9
10–3
12–2
11–1
9–8
38 x 235
5.05
4.59
4.01
4.75
4.32
3.72
2 x 10
16–7
15–1
13–2
15–7
14–2
12–3
38 x 286
6.14
5.58
4.68
5.78
5.25
4.32
2 x 12
20–2
18–4
15–4
19–0
17–3
14–2
No. 1 and No. 2
Continued on p. 298