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Table 29 Maximum spans for roof joists – specified roof snow loads 1.0 to 2.0 kPa (20.9 to 41.8 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)
1.0 (20.9)
1.5 (31.3)
2.0 (41.8)
Joist Spacing, mm (in.)
Joist Spacing, mm (in.)
Joist Spacing, mm (in.)
Joist Size, mm
300
400
600
300
400
600
300
400
600
Grade
in.
12
16
24
12
16
24
12
16
24
No. 1 and No. 2
38 x 89
2.59
2.36
2.06
2.27
2.06
1.80
2.06
1.87
1.63
2x4
8–6
7–9
6–9
7–5
6–9
5–11
6–9
6–2
5–4
38 x 140
4.08
3.71
3.24
3.57
3.24
2.83
3.24
2.94
2.57
2x6
13–5
12–2
10–8
11–8
10–8
9–3
10–8
9–8
8–5
38 x 184
5.36
4.87
4.26
4.69
4.26
3.72
4.26
3.87
3.38
2x8
17–7
16–0
14–0
15–4
14–0
12–2
14–0
12–8
11–1
38 x 235
6.85
6.22
5.44
5.98
5.44
4.74
5.44
4.94
4.22
2 x 10
22–6
20–5
17–10 19–8
17–10 15–7
17–10 16–2
13–10
38 x 286
8.34
7.57
6.40
6.62
5.50
6.62
6.00
4.90
2 x 12
27–4
24–10 21–0
23–11 21–9
18–1
21–9
19–8
16–1
38 x 89
2.59
2.36
2.06
2.27
2.06
1.80
2.06
1.87
1.63
2x4
8–6
7–9
6–9
7–5
6–9
5–11
6–9
6–2
5–4
38 x 140
4.08
3.71
3.24
3.57
3.24
2.83
3.24
2.94
2.57
2x6
13–5
12–2
10–8
11–8
10–8
9–3
10–8
9–8
8–5
38 x 184
5.36
4.87
4.26
4.69
4.26
3.72
4.26
3.87
3.38
2x8
17–7
16–0
14–0
15–4
14–0
12–2
14–0
12–8
11–1
38 x 235
6.85
6.22
5.44
5.98
5.44
4.75
5.44
4.94
4.32
2 x 10
22–6
20–5
17–10 19–8
17–10 15–7
17–10 16–2
14–2
38 x 286
8.34
7.57
6.62
6.62
6.62
6.01
5.25
2 x 12
27–4
24–10 21–9
18–11 21–9
19–9
16–10
No. 1 and No. 2
7.28
7.28
23–11 21–9
5.77
Continued on p. 296