Guide
Colorbond roof cleaning, without taking the coating off
A Colorbond roof is steel with a painted coating, and the coating is the part doing the work. Clean it gently and it lasts. Blast it and the dirt comes off along with some of the finish. The manufacturer's own line is that it needs minimal maintenance, and that rain does most of the cleaning for you.
So the honest answer to how a Colorbond roof should be cleaned is: less often than people think, at low pressure, and with the rainwater tank and the downpipes dealt with first.
What the manufacturer says
On its roofing page, Colorbond says the steel requires minimal maintenance and that natural rain keeps it looking good for many years. The parts rain does not reach are the exception. Under eave cladding, garage doors and the undersides of gutters should be hosed down about twice a year, and more often near the sea.
That is worth knowing before you pay anyone. On a roof with nothing growing on it, a hose on the sheltered parts is the maintenance. A full clean is for mould and lichen, for black streaking under trees, and for a roof that has gone years without rain reaching some of it.
Source: Colorbond roofing, product page, read 23 October 2026.
The four mistakes
High pressure close to the sheet
It strips coating along with the dirt, and coating cannot be washed back on.
Scourers and stiff brushes
Anything abrasive scuffs the finish. If dirt will not rinse off, the answer is chemistry and time, not elbow grease.
Forgetting the tank
A roof that feeds a rainwater tank sends whatever is on it into the tank. Disconnect first, reconnect last.
Hosing it all into the gutter and away
Roof wash water is still wash water. It is kept out of the stormwater drain like any other.
How we clean one, in order
Look at the sheet
Colorbond, bare zinc finish, or corrugated cement sheet. The last one stops the job until it has been assessed for asbestos.
Deal with the water paths
Tank downpipes disconnected or diverted. Stormwater downpipes blocked, and the wash water directed to a holding point.
Reach it the safe way
SafeWork NSW puts working from the ground or solid construction first. Walking the roof comes after a ladder and the edge have been ruled out.
Apply, then wait
A cleaning solution at low pressure, given time to kill the growth rather than being pushed at it.
Rinse top down
With the slope and the laps, never up under them, so nothing is driven back under a sheet.
Put it back
Downpipes reconnected, tank reconnected after the roof has been rinsed, and anything we noticed on the roof photographed for you.
What it costs
Our soft wash on a single storey metal or Colorbond roof is from $899 including GST. Roof area moves it most. A second storey carries our published loading of plus 30%. Gutters on the same visit are $249 for a single storey.
For the wider market, a Sydney operator cost guide prices roof cleaning of all materials by area, from $350 for a small roof to $1,500 and over for a very large one, as at 3 September 2026. The full breakdown and a calculator are on the roof cost page.
Colorbond roof questions
Does a Colorbond roof need cleaning?
Less than most roofs. The manufacturer says the steel needs minimal maintenance and that rain keeps it looking good. The parts rain does not reach, like the underside of gutters and sheltered cladding, are the parts it says to hose down, about twice a year and more often near the sea. A full roof clean is for growth, heavy grime or a roof about to be inspected or sold.
Can you pressure wash a Colorbond roof?
You can point a pressure washer at one, and that is the problem. The coating is what protects the steel, and a lance held close takes it with the dirt. We soft wash metal roofs: low pressure, a cleaning solution given time to work, then a rinse.
What about the rainwater tank?
If the roof feeds a tank, the downpipe to it is disconnected or diverted before anything is applied, and stays that way until the roof has been rinsed and the rinse water has gone somewhere else. Cleaning solution does not belong in drinking or garden water.
How much does Colorbond roof cleaning cost in Sydney?
Our soft wash on a single storey metal or Colorbond roof is from $899 including GST. Area moves it most. A Sydney operator cost guide prices roofs of all materials from $350 for a small roof to $1,500 and over for a very large one.
Will walking on it dent it?
It can, if it is stood on in the wrong place. Fewer footsteps is better for any roof, so the first question is whether it can be treated from a ladder or the edge rather than walked.
My roof is corrugated but grey and flat looking. Is it Colorbond?
It might be corrugated cement sheet, which can contain asbestos. Asbestos NSW names corrugated roofing among the commonest asbestos products in houses. If there is any doubt we stop, and nobody washes it until it has been assessed.