The Victorian Building Authority (VBA) provides advice to assist plumbers, roofers and builders when specifying box gutters, and designing structures that will house a box gutter. Considering the below factors when designing your box gutters will help to ensure your work is compliant.

  • Not flatter than 1:200 for sole widths equal to or less than 600mm wide
  • Deviations from the gradients must be smooth and prevent permanent ponding
  • Made from material compatible with box gutter material (ask us if you need help with this)
  • UV resistant if positioned in direct sunlight
  • Secured to building structure
  • No other services attached to box gutter support structure
  • Give consideration to potential environmental corrosion and take preventative steps to guard against it
  • Secure to prevent longitudinal movement, unless designed to allow for thermal eect
  • Must be able to support the entire weight of gutter and sumps when full of water, plus tracable load
    at any point in gutter and sumps
  • Must discharge to rainhead or sump
  • Must include independent overflow discharging into atmosphere
  • Min width 300mm (commercial), 200mm (domestic)
  • Min depth 75mm high end
  • Sole width which is not reduced towards the outlet without a proportional increase in depth
  • Discharge at downstream end without change in direction (ie – not to the side)
  • Box gutter must be straight (no change in direction)
  • Must be sealed to rainheads and sumps

Box Gutters installations must meet the following Australian Standards and Plumbing regulations requirements:

  • AS/NZS 3500.3 Plumbing and drainage Part 3: Stormwater Drainage
  • AS/NZS 3500. Plumbing and drainage Part 5: House Installations
  • SA HB 39 installation code for metal roof and wall cladding
  • SAA/SNZ HB114 guidelines for the design of eaves and box gutters

(Source: Victorian Building Authority Fact Sheet – Box Gutter Design as of 31/3/2021)

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