Built before 1990? Check for asbestos first
The NSW EPA says a home built before 1990 probably contains some asbestos, and old cement roof sheeting and 'slates' are common places for it. ASSEA says pressure cleaning asbestos roofs has spread fibres to neighbouring properties, footpaths and stormwater, with clean-ups costing hundreds of thousands of dollars. If in doubt, have a sample tested before anyone cleans.
What builds up on Sydney roofs
Moss where the rain is heaviest
Sydney gets rain on 95.2 days a year on average at Observatory Hill, and much more falls on the upper north shore, around 1,400 mm a year at Turramurra. Damp, shaded roofs there grow moss and lichen, most of all on unglazed terracotta. Monier says the growth sits on the surface and doesn't harm the tile itself.
Salt near the beaches
Rain rinses most of a metal roof, but BlueScope's October 2026 bulletin says sheltered spots, like gutter undersides and cladding under the eaves, should be washed every three months near the coast where there's salt spray. Near Manly, Bondi or the exposed parts of the harbour, that's simple routine upkeep for the steel.
Old terracotta doesn't like pressure
Federation homes in Haberfield and Paddington were built with terracotta tiles, and original tiles that age can be brittle. Monier strongly advises against pressure washers on roof tiles because of the risk of damage, and NSW's heritage inspection schedule warns against walking on brittle tiles.
How Sydney roofs should be cleaned
On tiles, a low-pressure wash with a moss and lichen treatment is gentler than a high-pressure blast, and it doesn't drive water up under the laps. On metal, BlueScope suggests household detergent and water with a mop or soft nylon broom, and warns against solvents such as turpentine or thinners and against hard bore water.
Cleaning is often the first step of a roof restoration or roof painting job, so if you're planning either, get them quoted together. For heavy moss, our moss and lichen removal page explains the options.
What to ask a Sydney roof cleaner
- What pressure and what chemicals will you use on my tiles or metal?
- Have you checked whether my roof could be asbestos cement?
- How will you protect the gutters, downpipes and garden from run-off?
- Will you replace any tiles you crack, and at whose cost?
- Do you hold public liability insurance?
What you can do, and what to leave
You can
- Hose down sheltered metal spots you can reach from the ground, like gutter undersides and eaves cladding
- Trim branches that shade the roof and drop leaves on it
- Photograph moss build-up from the yard so a cleaner can quote
Leave to a roofer
- Any work up on the roof itself, especially on old terracotta
- Any cleaning of a roof that might be asbestos
- Chemical moss treatments on a roof that drains to a water tank
If it were our roof
We'd rule out asbestos first on any pre-1990 roof. On sound tiles with moss, we'd pay for a soft wash and treatment, not a high-pressure blast. Near the beach we'd hose the sheltered metal spots ourselves every few months, which costs nothing. Our national roof cleaning page covers methods, and the Sydney roofing hub explains the 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.