BOX GUTTERS - ALLOWABLE WIDTH, SLOPE, AND LENGTH

To AS/NZS 3500.3.2:2003 "Stormwater Drainage Acceptable Solutions".


MINIMUM WIDTH = 300 mm for Commercial construction, and 200 mm for Domestic construction.
REQUIRED GUTTER SLOPE 1:40 TO 1:200

There is always some confusion as to how the slope affects the overall Depth. The depth shown in the calculations is at the upstream end. Therefore any slope on the gutter will make the downstream end deeper, or the flashing longer.

MAXIMUM ALLOWABLE LENGTH Between expansion joints.
Material Base Metal Thickness (mm) Max Length (metres) Minimum expansion space (mm)
Aluminum 0.90 12 50
Copper 0.60 9 50
Copper 0.80 15 50
Copper 1.0 26 50
Steel Colorbond Zincalume 0.55 20 50
Steel 0.75 25 50
Stainless Steel 0.55 20 50
PVC - 10 30
Zinc 0.80 10 50