If there is one detail we repeatedly see in major defects, claims, and disputes, it is box gutters.
Box gutters are not prohibited, but they are extremely high-risk and require precise design, installation, and ongoing maintenance to remain compliant.
Box gutters must comply with NCC 2022 Volume 2 H2D6, AS/NZS 3500.3, AS 1562.1, and HB 39. This includes correct sizing for rainfall intensity, correct falls, compliant overflow provisions, correct joints, corrosion protection, and access for maintenance.
In practice, we regularly see box gutters that are undersized, have insufficient fall, lack compliant overflow, fill with debris, rust from the inside out, and ultimately overflow into the building cavity.
When this occurs, water enters the structure rather than discharging outside. This turns a roofing issue into major building damage.
Even when installed correctly, box gutters require regular maintenance to remain compliant. If the homeowner does not maintain them, the system fails — and the liability argument often returns to the builder because the system itself is inherently high risk.
At design stage, the best question to ask is: “Can we eliminate the box gutter entirely?”
Often a minor redesign can replace a box gutter with external eaves gutters, split roof lines, or a different roof direction. Removing the box gutter removes one of the largest future defect risks in the home.
If you have any questions or need further guidance, please don’t hesitate to contact our Advisory team:
📞 (02) 6175 5900
📧 workplace@mba.org.au
