Technical Booklet D Structure·Page 43·Table 4B.24
Table 4B.24 Maximum clear span of purlins supporting rafters
Table providing maximum clear spans in metres for timber purlins supporting rafters with C16 strength class, roof pitch between 22.5° and 30°, and 1.00 kN/m² imposed load. Spans vary by purlin size, spacing, and dead load category.
Table 4B.24 Maximum clear span of purlins supporting rafters (m); Roof pitch more than 22.5° but not more than 30°; Imposed load of 1.00 kN/m2; Timber strength class C16
Dead Load [kN/m2] excluding the self weight of the purlin
Size of purlin (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
Design spacing of purlins (mm): 1500, 1800, 2100, 2400, 2700, 3000
47 x 150: 2.09, 1.96, 1.85, 1.98, 1.85, 1.88
47 x 175: 2.09, 1.96, 1.85, 1.98, 1.85, 1.88
47 x 200: 2.39, 2.24, 2.11, 1.98, 1.86, 2.26, 2.11, 1.96, 1.83, 2.15, 1.98, 1.83
47 x 225: 2.69, 2.51, 2.37, 2.21, 2.08, 1.97, 2.54, 2.37, 2.19, 2.05, 1.92, 1.82, 2.42, 2.22, 2.05, 1.91
63 x 150: 2.00, 1.87, 1.89, 1.88
63 x 175: 2.33, 2.18, 2.06, 1.96, 1.88, 1.80, 2.20, 2.06, 1.95, 1.85, 2.10, 1.96, 1.85
63 x 200: 2.66, 2.49, 2.35, 2.24, 2.14, 2.05, 2.51, 2.35, 2.22, 2.12, 2.00, 1.90, 2.40, 2.24, 2.12, 1.99, 1.87
63 x 225: 2.98, 2.80, 2.65, 2.52, 2.41, 2.29, 2.83, 2.65, 2.50, 2.38, 2.24, 2.12, 2.69, 2.52, 2.38, 2.22, 2.09, 1.98
75 x 150: 2.12, 1.99, 1.88, 2.01, 1.88, 1.92
75 x 175: 2.47, 2.32, 2.20, 2.09, 2.00, 1.93, 2.34, 2.20, 2.08, 1.98, 1.89, 1.82, 2.24, 2.09, 1.98, 1.88, 1.80
75 x 200: 2.82, 2.65, 2.51, 2.39, 2.29, 2.20, 2.68, 2.51, 2.37, 2.26, 2.16, 2.08, 2.55, 2.39, 2.26, 2.15, 2.05, 1.94
75 x 225: 3.17, 2.98, 2.82, 2.68, 2.57, 2.47, 3.01, 2.82, 2.67, 2.54, 2.43, 2.32, 2.87, 2.69, 2.54, 2.42, 2.29, 2.17
2 x 47 x 200: 3.20, 3.00, 2.85, 2.72, 2.60, 2.51, 3.03, 2.85, 2.70, 2.57, 2.47, 2.37, 2.90, 2.72, 2.57, 2.45, 2.35, 2.26
2 x 47 x 225: 3.59, 3.37, 3.20, 3.05, 2.93, 2.82, 3.41, 3.20, 3.03, 2.89, 2.77, 2.67, 3.25, 3.05, 2.89, 2.76, 2.64, 2.54
2 x 47 x 250: 3.98, 3.74, 3.55, 3.39, 3.25, 3.13, 3.78, 3.55, 3.36, 3.21, 3.08, 2.96, 3.61, 3.39, 3.21, 3.06, 2.93, 2.82
2 x 47 x 275: 4.37, 4.11, 3.90, 3.72, 3.57, 3.44, 4.15, 3.90, 3.70, 3.53, 3.38, 3.26, 3.97, 3.73, 3.53, 3.36, 3.22, 3.08
2 x 47 x 300: 4.77, 4.48, 4.25, 4.06, 3.89, 3.75, 4.53, 4.25, 4.03, 3.84, 3.69, 3.55, 4.32, 4.06, 3.85, 3.67, 3.51, 3.35
C16
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