Chart 1 Dr ainage holes for overlapping surfaces steel thickness 12 125 cm Overlapping surf ace po2 cm2 Holes Unw elded surf aces 1 6 1 03 None None 1 6 et 64 1 03 4 1 3 38 1 cm 1 25 cm 64 et 400 4 1 3 2580 12 1 25 cm 2 5 cm each increment o f 400 2580 34 2 cm 4 1 0 cm Chart 2 Dr ainage holes for overlapping surfaces steel thickness 12 125 cm Overlapping surf ace po2 cm2 Holes Unw elded surf aces 1 6 1 03 None None 1 6 et 64 1 03 4 1 3 None None 64 et 400 4 1 3 2580 12 1 25 cm 2 5 cm each increment o f 400 2580 34 2 cm 4 1 0 cm 25