Table 4B.38: Maximum clear span of flat roof joists for access only

Table 4B.38 Maximum clear span of flat roof joists (m); Access only for cleaning and maintenance; Imposed load 1.00 kN/m²; Timber strength class C24 C24 Dead Load [kN/m²] excluding the self weight of the joist Size of joist (mm) and joist spacing (400mm, 450mm, 600mm) with dead loads: - Not more than 0.50 kN/m² - More than 0.50 but not more than 0.75 kN/m² - More than 0.75 but not more than 1.00 kN/m² Joist sizes and maximum spans (in metres): 38 x 97: 1.84-1.76 / 1.76-1.66 / 1.69-1.59 38 x 120: 2.50-2.37 / 2.37-2.22 / 2.27-2.11 38 x 145: 3.18-2.86 / 3.00-2.71 / 2.85-2.59 38 x 170: 3.77-3.30 / 3.58-3.13 / 3.40-2.99 38 x 195: 4.31-3.78 / 4.10-3.59 / 3.93-3.43 38 x 220: 4.85-4.25 / 4.61-4.04 / 4.42-3.86 47 x 97: 2.03-1.94 / 1.94-1.83 / 1.86-1.74 47 x 120: 2.74-2.55 / 2.60-2.42 / 2.48-2.30 47 x 145: 3.47-3.07 / 3.27-2.91 / 3.11-2.79 47 x 170: 4.03-3.54 / 3.84-3.36 / 3.68-3.22 47 x 195: 4.61-4.05 / 4.39-3.85 / 4.21-3.68 47 x 220: 5.18-4.56 / 4.94-4.33 / 4.73-4.15 50 x 97: 2.08-1.99 / 1.99-1.88 / 1.91-1.79 50 x 120: 2.81-2.60 / 2.66-2.47 / 2.54-2.36 50 x 145: 3.56-3.13 / 3.35-2.97 / 3.19-2.85 50 x 170: 4.11-3.61 / 3.92-3.43 / 3.75-3.28 50 x 195: 4.70-4.13 / 4.48-3.93 / 4.29-3.76 50 x 220: 5.28-4.65 / 5.04-4.42 / 4.83-4.23 63 x 97: 2.31-2.20 / 2.20-2.07 / 2.11-1.97 63 x 120: 3.10-2.81 / 2.93-2.67 / 2.80-2.56 63 x 145: 3.84-3.38 / 3.66-3.21 / 3.49-3.07 63 x 170: 4.42-3.89 / 4.21-3.70 / 4.04-3.54 63 x 195: 5.05-4.45 / 4.81-4.24 / 4.62-4.06 63 x 220: 5.67-5.00 / 5.41-4.76 / 5.19-4.56 75 x 120: 3.33-2.97 / 3.14-2.83 / 2.99-2.71 75 x 145: 4.05-3.57 / 3.86-3.40 / 3.71-3.25 75 x 170: 4.66-4.11 / 4.45-3.92 / 4.27-3.75 75 x 195: 5.32-4.70 / 5.08-4.48 / 4.88-4.29 75 x 220: 5.97-5.28 / 5.70-5.04 / 5.48-4.83 38 x 140: 2.99-2.72 / 2.82-2.59 / 2.69-2.47 38 x 184: 4.07-3.57 / 3.87-3.39 / 3.71-3.24 CLS/ALS