A leaking box gutter can cause problems beyond the roof.
A box gutter sits between roof planes or behind a parapet, usually with a shallow fall, and collects water from a large roof area. Because it cannot simply spill over the edge like an eaves gutter, it needs to be sized for heavy rain, laid to drain properly and given a dedicated outlet and overflow arrangement, such as a sump or rainhead, so water has a safe way out if the outlet blocks.
Repair local damage. Replace deteriorated sections when needed.
New and replacement box gutters must comply with applicable Victorian building and plumbing requirements. Replacement is therefore the point at which an undersized gutter, poor drainage or a missing overflow can be corrected rather than repeated.
Find out why the box gutter is failing.
Inspect
Check the sole for ponding, corrosion and failed laps, the sump and outlet for blockage, and whether an independent overflow exists.
Decide
Compare the remaining sound metal and fall against the damage, and decide between a local repair and a rebuild.
Complete
Complete the agreed scope, including the sump, outlet or overflow detail and adjoining flashings where they form part of the work.
Check the drainage details around the gutter.
Eaves gutters that feed the box gutter, and the roof flashings along its edges, are separate components with separate faults. Where the inspection finds problems there, they are assessed alongside the box gutter.
Gutter Repairs & ReplacementSee box-gutter and roof drainage work.
The McKinnon office roof replacement included renewed box-gutter components, and the Hampton project addressed a roof arrangement that sent runoff from opposing slopes to a shared gutter.
Box gutters — common questions
Why must a box gutter have an overflow path?+
A box gutter sits inside the roof line, so if the outlet blocks, the water has nowhere to go but into the building. Blocked drainage therefore needs a planned escape route, usually an overflow weir or rainwater head that discharges outside the building.
Can a box gutter be lined instead of replaced?+
A lining or coating can extend life when the gutter is structurally sound, clean and has adequate fall. It does not fix ponding or rust-through, and in those cases the gutter generally needs replacing or rebuilding.
How does debris cause box gutter leaks?+
Leaves and silt gather at sumps and outlets, hold water and speed corrosion of the metal and joints. Clearing before autumn and after storms is a common routine, and more often near trees.
Why does water from a box gutter appear somewhere else inside?+
Water follows the framing, sarking and ceiling lining before it shows. The stain location rarely marks the leak, so the gutter, outlets and nearby flashings are all checked together.
What signs show a box gutter needs replacement?+
Widespread corrosion, patched areas that keep failing, ponding that remains after clearing and rusted-through joints indicate that isolated repairs are no longer worthwhile.