When Perth's roof plumbing gets tested
Cyclone remnants
The outer bands of decaying Tropical Cyclone Narelle brought 62.8 mm to Perth and 102.8 mm to Mandurah on 28 March 2026. Rain that heavy shows up undersized downpipes and blocked outlets within minutes.
Hail in the drains
In the March 2010 storm, hail blocked gutters and drains, which made the flooding worse. Once a gutter outlet is choked, water backs up and can spill inside the eaves or into the roof space.
Makuru rain
June and July are Perth's coldest, wettest months, with more frequent storms, and August is close behind. That's when leaking flashings and overflowing box gutters tend to show themselves.
Salt and gutter steel
BlueScope's gutter bulletin recommends standard Colorbond and Zincalume eave gutters more than 200 m from salt marine influence, and Colorbond Ultra more than 100 m. Homes near the beach or the Swan River estuary should ask which applies to them.
What a roof plumber checks
Downpipes. Under the National Construction Code, one downpipe can serve no more than 12 m of gutter, and downpipes must sit as close as possible to valley gutters. A long run of gutter with a single downpipe at the far end can be why gutters spill in a downpour.
Fall and overflow. The Code calls for eaves gutters with a fall of at least 1:500 (a gentle slope toward the outlet) and a way for overflow to escape outside the house, such as a slotted front.
Box gutters and flashings. Box gutters sit inside the roof line, so when they overflow the water ends up indoors. Flashings where the roof meets a wall or chimney crack and lift over time.
Metals that don't mix. BlueScope says galvanised gutters can corrode early under a Colorbond, Zincalume or glazed terracotta roof, and that air conditioner condensate should be piped to the ground, not into a gutter.
Who's licensed for what. In WA, only a plumber licensed by the Plumbers Licensing Board can do water supply, sanitary and drainage plumbing. Building and Energy's rainwater tank diagrams show the pipe from gutter to tank as non-regulated work, while pipework from the tank to the house is regulated. Check any licence on the WA Online Licence Search.
Questions to ask a Perth roof plumber
- Are there enough downpipes for the length of my gutters?
- Do my box gutters have overflows, and where does the water go if they fill?
- What licence or registration do you hold for this work, and can I check it?
- Will the new gutters and flashings suit my distance from the coast or river?
- Is the stormwater pipe after the downpipe blocked too?
What you can check, and what needs a roof plumber
You can
- Keep downpipe outlets and ground grates clear of leaves
- Watch the gutters from under cover in heavy rain and note where they spill
- Look for rust streaks and drips at gutter joints from the ground
Leave to a roofer
- Box gutters and anything inside the roof line
- Flashings where the roof meets walls or chimneys
- Adding or resizing downpipes and outlets
- Any work near a roof that might be asbestos cement
How we'd approach it
If your gutters spilled in a downpour, we'd ask the roof plumber to check capacity, not just clean them out. A clean clears a blockage; it doesn't fix a run that's too long for one downpipe or a box gutter with nowhere to overflow. Fix that before winter and the next cyclone remnant is far less of a worry.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.
Tell us what's overflowing and your postcode. If we have a licence-checked roof plumber for your area of Perth, we'll pass the job to that one business; if not, we'll tell you straight away. Our main roof plumbing page and the Perth hub have more.