A box gutter sits inside the roof, not hanging off the edge. When it blocks up or a joint lets go, the water doesn’t spill onto the garden. It goes straight into your ceiling. We inspect, water test, repair and replace box gutters on Melbourne homes, terraces, apartments, shops and warehouses, and we show you what’s actually wrong before you spend a dollar on the fix.
Call us 24/7: 03 8583 2640 or 0426 204 244
Why box gutters cause so much grief
G’day, I’m Victor from Holy Mess Repairs. A lot of the leaks we chase in Melbourne end up at a box gutter. Most of the time it isn’t one thing. It’s a sump full of sludge, a joint that’s been siliconed three times, a gutter that’s lost its fall and holds water, and no overflow to get rid of it when it backs up.
Slapping more silicone on the joint you can see doesn’t fix that. You need to know why the water’s sitting there in the first place, then fix the cause.
Signs your box gutter is the problem
- Water stains or drips along an internal wall or the middle of a ceiling, not just near the eaves
- Leaks that only show up in heavy rain or when leaves come down
- Water ponding in the gutter days after rain
- Rust, flaking metal or lots of old silicone on the joints
- A sump or rainhead that’s always full of sludge
- No overflow you can see. If the outlet blocks, the water has nowhere to go but inside
How we fix a box gutter
- We inspect it properly. We check the width, the fall, the sumps and outlets, every joint and whether there’s a working overflow.
- We clean it and water test it. Once the sludge is out, we run water through it. If the leak still isn’t obvious, we dye test it so we know exactly which joint or section is letting go.
- You get photos and video. You see what’s failing and why.
- You choose the fix. Usually that’s a clean and reseal, replacing a section, or a full new box gutter with new sumps and flashings.
- We do the work and flow test it before we leave, so you know the water goes where it should.
For roof plumbing work over $750 in Victoria, we issue a compliance certificate, as the law requires.
Clean and reseal, or replace?
A clean and reseal makes sense when:
- The metal is still sound and the problem is failed sealant at the joints
- The sump is blocked, but the gutter itself is in decent shape
- You need to stop the leak now and plan a replacement later
Replacement makes sense when:
- There’s rust coming through the gutter or the joints
- The gutter is too narrow, has no fall or holds water
- There’s no proper overflow, and the sump or rainhead needs redesigning anyway
- It’s been patched before and keeps failing
We’ll tell you straight which one your gutter needs. If a reseal will do the job, we’ll say so.
Box gutters we see across Melbourne
Terraces and older inner-city homes
Victorian and Edwardian terraces often have box gutters along party walls and behind parapets. They’re usually narrow and old, and they’ve been patched for decades. When one fails, the water often comes out a room or two away.
Apartments, units and strata
On apartment buildings, box gutters and sumps collect water from big roof areas. An undersized or blocked sump can back up fast. We work with owners corporations and strata managers, and the photos and report make it easy to approve the work.
Shops, offices, restaurants and warehouses
Commercial roofs often have long box gutters next to air-con units and other plant. Rust and debris from that plant wash into the gutter and block the sump. A failed commercial box gutter can put water through the ceiling onto staff, stock or customers.
New builds and builders
We’ve inspected new homes where the box gutter areas were ponding and relying on silicone instead of proper turn-downs and folds. If you’re a builder or owner wanting an independent check before final payment, see our roof reports page.
Watch: box gutter work
What does box gutter work cost?
Typical box gutter prices (a rough guide only, plus GST):
- Small repair (one failed joint or a blocked sump cleared): about $350–$900
- Clean and reseal a full run, or reline it: about $1,500–$4,000
- Replacement: about $250–$750 per metre, and often more once new sumps, flashings, an overflow, height or plant on the roof are added
These numbers vary a lot from job to job. They’re based on what licensed roof plumbers and published cost guides in Melbourne, Canberra and around Australia charge in 2026. We always quote after we’ve inspected your gutter.
To give you a real example, here’s what one recent Melbourne commercial quote came to, for about 12 metres of box gutter with a blocked sump and a failed, rusting joint:
- Clean and reseal (clear the sump and channel, strip old silicone and rivets, reseal and re-rivet every joint, flush test): $3,000 + GST
- Full replacement (remove the old 12 m gutter and sumps, new Colorbond or Zincalume box gutter, two new sumps, 8 m of new apron flashing, flush test): $10,500 + GST
Price depends on:
- Length, width and access (height, plant, parapets)
- The state of the sumps, outlets and flashings
- Whether you need an overflow added or redesigned
- Whether scaffolding or a lift is needed
If we can’t tell where the leak is coming from, we may suggest a dye test first, so you only pay to fix the sections that are actually failing.
Real Melbourne box gutter jobs
Dandenong: blocked sump and a failed joint on an office roof
A professional office had a box gutter of about 12 m running next to large air-con units. We found the sump almost completely blocked with sludge, so water was backing up along the channel. One joint’s sealant had completely failed, with rust underneath. Rust flaking off the air-con ducting was washing into the gutter and adding to the blockage. We gave the owner two options: a full clean and reseal at $3,000 + GST, or a full replacement with new sumps and apron flashing at $10,500 + GST.
Northcote: box gutter joints on a restaurant’s old metal roof
During a full day of dye testing on an aged corrugated roof, the box gutters were part of the problem: failed joints with water ponding, a rusty kitchen sump and gutters that had lost their fall as the building moved. The targeted repair option included grinding, pop-riveting and sealing the box gutter joints and coating the sump, followed by a repeat dye test. See the full write-up on our dye testing page.
Mont Albert: a corroded box gutter on a large metal roof
On a roughly 420 m² metal roof, the box gutter along the parapet was heavily rusted, with ponding that pointed to poor fall. A layout with a change of direction near the wall also looked unlikely to meet current box gutter rules. Patching rusted-through steel doesn’t last, so we put forward replacement options alongside cheaper short-term choices.
Balwyn North: new build, box gutter areas ponding
On an independent inspection of a brand-new roof, the metal and box gutter areas had standing water, water dripping off the low edges, heavy reliance on silicone and unfinished turn-downs. We listed each defect for the roof plumber to fix before final payment.
Warranty, in plain words
The warranty on a box gutter job follows the type of work and the materials used, and matches the material supplier’s warranty. A clean and reseal is a repair. It buys you time, and its warranty follows the sealant supplier’s. A new Colorbond or Zincalume box gutter carries the steel supplier’s warranty, and we register BlueScope warranties for you where they apply. Whatever you choose, we’ll tell you in writing what’s covered and for how long before you decide.
Why Holy Mess Repairs
- Licensed roof plumbers. Victorian roof plumbing licence 32176, recognised Australia-wide (including the ACT) under mutual recognition laws.
- Compliance certificate for regulated roof plumbing work over $750.
- Rated by real customers. Around 4.4 stars from 120+ Google reviews.
- Insured, with photos and video of what we find and what we did.
- Straight advice. We’ll tell you if a reseal will do, or if it really needs replacing.
- Open 24/7.
Box gutter FAQs
What is a box gutter?
It’s a gutter built into the roof, usually between two roof sections, behind a parapet or along a wall, instead of hanging off the edge. Because it sits over the building, a leak or overflow goes inside.
Why does my box gutter overflow inside?
Usually it’s a blocked sump or outlet, a gutter that’s too small or has lost its fall, or no proper overflow. When the water can’t get out, it rises over the side and into the ceiling.
Can a leaking box gutter be repaired, or does it need replacing?
If the metal is sound and the problem is failed sealant, a clean and reseal can work well. If it’s rusting through, holding water or keeps failing, replacement is usually the better money.
How much does it cost to fix a box gutter in Melbourne?
As a rough guide: about $350–$900 + GST for a small repair, $1,500–$4,000 + GST to clean and reseal or reline a full run, and $250–$750 + GST per metre to replace, often more once sumps, flashings and access are added. We quote after we inspect. As a real example, one recent 12 m commercial box gutter was quoted at $3,000 + GST to clean and reseal, or $10,500 + GST to replace with new sumps and flashing.
Do you add overflows?
Yes. Where a box gutter has no proper overflow, we’ll recommend one as part of the repair or replacement.
Do you give a compliance certificate?
Yes. In Victoria, roof plumbing work over $750 needs a compliance certificate, and we issue it.
Can you find which part of the box gutter is leaking?
Yes. We water test it, and if it’s still not clear we dye test it to pin down the exact joint or section.
Do you work with strata and commercial clients?
Yes. We work with owners corporations, strata managers, property managers and business owners, and we give you photos and options you can take to a committee.
Get your box gutter sorted properly
Stop patching the same joint every winter. Call us and we’ll find out why it’s failing and give you clear options.
Call Victor and the team, 24/7: 03 8583 2640 or 0426 204 244
Holy Mess Repairs · Unit 10, 238–244 Edwardes St, Reservoir VIC 3073 · Serving Melbourne and surrounding areas
In Canberra? See box gutter repairs in Canberra. Not sure where the leak is? See leak detection and dye testing.