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Table 33 Maximum spans for ceiling joists – attic not accessible by a stairway Maximum Span, m (ft.–in.) Commercial Designation Douglas fir – larch (includes Douglas fir and western larch)
Hem – fir (includes western hemlock and amabilis fir)
Spruce, pine, or fir (includes spruce [all species except coast sitka spruce], jack pine, lodgepole pine, balsam fir and alpine fir)
Northern Species (includes any Canadian species covered by the NLGA Standard Grading Rules)
Grade No. 1 and No. 2
No. 1 and No. 2
No. 1 and No. 2
No. 1 and No. 2
Joist Size, mm (in.)
Joist Spacing, mm (in.) 300
(12)
400 (16)
600 (24)
38 x 89
(2 x 4)
3.27
(10–9)
2.97 (9–9)
2.59 (8–6)
38 x 140
(2 x 6)
5.14
(16–10)
4.67 (15–4)
4.08 (13–5)
38 x 184
(2 x 8)
6.76
(22–2)
6.14 (20–2)
5.36 (17–7)
38 x 235
(2 x 10)
8.63
(28–4)
7.84 (25–9)
6.85 (22–6)
38 x 286
(2 x 12)
10.50 (34–5)
9.54 (31–3)
8.34 (27–4)
38 x 89
(2 x 4)
3.27
(10–9)
2.97 (9–9)
2.59 (8–6)
38 x 140
(2 x 6)
5.14
(16–10)
4.67 (15–4)
4.08 (13–5)
38 x 184
(2 x 8)
6.76
(22–2)
6.14 (20–2)
5.36 (17–7)
38 x 235
(2 x 10)
8.63
(28–4)
7.84 (25–9)
6.85 (22–6)
38 x 286
(2 x 12)
10.50 (34–5)
9.54 (31–3)
8.34 (27–4)
38 x 89
(2 x 4)
3.11
(10–3)
2.83 (9–3)
2.47 (8–1)
38 x 140
(2 x 6)
4.90
(16–1)
4.45 (14–7)
3.89 (12–9)
38 x 184
(2 x 8)
6.44
(21–1)
5.85 (19–2)
5.11 (16–9 )
38 x 235
(2 x 10)
8.22
(27–0)
7.47 (24–6)
6.52 (21–5)
38 x 286
(2 x 12)
10.00 (32–10)
9.09 (29–10)
7.94 (26–1)
38 x 89
(2 x 4)
2.81
(9–3)
2.55 (8–5)
2.23 (7–4 )
38 x 140
(2 x 6)
4.42
(14–6)
4.02 (13–2)
3.51 (11–6)
38 x 184
(2 x 8)
5.81
(19–1)
5.28 (17–4)
4.61 (15–2)
38 x 235
(2 x 10)
7.42
(24–4)
6.74 (22–2)
5.89 (19–4)
38 x 286
(2 x 12)
9.03
(29–8)
8.21 (26–11)
7.17 (23–6)