Technical Booklet D Structure·Page 47·Table 4B.31
Table 4B.31: Maximum clear span of rafters for roof pitch 30–45°
This table specifies the maximum clear span in metres for timber rafters of various sizes supporting roofs pitched between 30° and 45°, with an imposed load of 1.00 kN/m² and C16 timber strength class. Spans are given according to rafter spacing (400, 450, or 600 mm) and dead load range.
Table 4B.31 Maximum clear span of rafters (m); Roof pitch more than 30° but not more than 45°; Imposed load 1.00 kN/m²; Timbers strength class C16 C16
Dead Load [kN/m²] excluding the self weight of the rafter
Size of rafter (mm) | Not more than 0.50 | More than 0.50 but not more than 0.75 | More than 0.75 but not more than 1.00
Spacing of rafters (mm) | 400 450 600 | 400 450 600 | 400 450 600
38 x 100 | 2.28 2.23 2.03 | 2.10 2.05 1.91 | 1.96 1.91 1.76
38 x 125 | 2.90 2.79 2.54 | 2.75 2.64 2.40 | 2.62 2.52 2.26
38 x 150 | 3.47 3.34 3.04 | 3.29 3.16 2.87 | 3.13 3.01 2.69
47 x 100 | 2.50 2.40 2.18 | 2.36 2.27 2.06 | 2.25 2.17 1.97
47 x 125 | 3.11 2.99 2.72 | 2.94 2.83 2.58 | 2.81 2.70 2.45
47 x 150 | 3.72 3.58 3.26 | 3.52 3.39 3.08 | 3.36 3.23 2.94
50 x 100 | 2.55 2.45 2.23 | 2.41 2.32 2.11 | 2.30 2.21 2.01
50 x 125 | 3.17 3.05 2.78 | 3.00 2.89 2.63 | 2.87 2.76 2.51
50 x 150 | 3.79 3.65 3.33 | 3.59 3.46 3.15 | 3.43 3.30 3.00
38 x 89 | 1.91 1.87 1.77 | 1.77 1.73 1.62 | 1.67 1.62 1.50
38 x 140 | 3.24 3.12 2.84 | 3.07 2.95 2.68 | 2.93 2.82 2.52
CLS/ALS | — | — | —
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