Why roof plumbing gets tested in Brisbane
Most of a year's rain in three days
Between 23 and 28 February 2022, between 400 and 1,100 mm of rain fell across the Brisbane City Council area, averaging 795 mm. Griffith University put that at about 80% of the city's average annual rainfall in 72 hours. No roof drainage is designed for every extreme, but properly sized gutters, enough downpipes and working overflows limit the damage.
North-side creeks broke their records
Kedron Brook recorded 893 mm in that event, against 661 mm in 1974 and 315 mm in 2011. The 2022 flood combined river, creek and overland flow, and north-side creek flooding beat previous records. Where your downpipes discharge matters when the ground is already saturated, so ask a roof plumber to check the stormwater connections too.
Overflow has to land outside
In rain like that, gutters overflow somewhere. The NCC requires eaves gutters to have an overflow path, such as slots in the front, a 10 mm gap at the back or a front edge set lower than the fascia, so the spill lands outside rather than in the eaves or ceiling. Existing homes don't have to meet current rules unless new work is done, so new gutters are the time to get it right.
What a roof plumber does
Typical jobs are replacing rusted gutters and downpipes, adding a downpipe where one is doing too much work, fixing box gutters that overflow inside, resealing flashings, and replacing worn valleys. Under the NCC, each downpipe can serve no more than 12 m of gutter and should sit as close as possible to valley gutters.
BlueScope also says air conditioner condensate should be piped to the ground rather than into the gutters, so that's worth sorting while the plumber is there.
Which QBCC licence covers what
Queensland splits this work across licence classes. The metal fascias and gutters class covers rainwater goods, fascias, gutters and external flashings, and the roof and wall cladding class covers rainwater goods too. The plumbing and drainage class needs a licence at any value, and anyone doing or supervising regulated plumbing also needs an occupational plumber and drainer licence.
The QBCC says an ad without a contractor name and QBCC licence number is a sign the operator may be unlicensed, and for plumbing work, the number has to appear in ads whatever the job's value.
What to ask a Brisbane roof plumber
- Which QBCC licence classes do you hold, and do you have a plumber and drainer licence for the stormwater side?
- Are there enough downpipes for the length of gutter, and are they close to the valleys?
- Do the gutters have overflow slots or a back gap, so water spills outside rather than into the eaves?
- Where will the downpipes and air conditioner drains discharge?
- Can you check the box gutter's overflow while you're up there?
How we'd approach it
We'd fix overflow problems before summer, starting with box gutters and valleys, because water that backs up there ends up inside the house. On the north side or in a low-lying street, we'd also ask where the downpipes discharge. The national roof plumbing page explains the work in more detail, and the Brisbane hub covers local conditions.
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.