What builds up on Central Coast roofs
Moss and lichen on the open coast
Norah Head records rain on 148.3 days a year, with humidity averaging 65%. A roof that seldom dries out suits moss and lichen, and unglazed terracotta grows more of it than concrete tile, Monier says.
Salt where the rain can't reach
Rain rinses most of a steel roof, but salt settles in the places it misses: under the eaves, on top of garage doors and on the underside of gutters. Near salt spray, hose those spots down every three months, which is what BlueScope's latest maintenance bulletin (October 2026) asks for.
Older roofs after a storm
If your house went up before 1990, part of the roof could be asbestos cement. ASSEA warns that storms can damage asbestos materials and that they should never be cleaned with high-pressure water afterwards, when broken sheets are most likely to shed fibres.
How each kind of roof should be cleaned
Tiles: Monier strongly advises against pressure washers because they can damage tiles, and recommends a professional roof cleaner instead. It also says moss on terracotta only grows on the surface and doesn't weaken the tile, so the aim is to remove it without harming the roof, not to blast it off.
Steel: BlueScope's approach for COLORBOND is plain water and a soft broom or mop, with mild household detergent if needed. Abrasive or solvent cleaners such as turpentine, petrol, kerosene or paint thinners are out, and so is hard bore water.
Asbestos cement: don't clean it at all. ASSEA's advice is to keep it sealed and in good condition and never use high pressure or abrasive methods. If you're not sure what your roof is, our asbestos checker helps you weigh the odds.
Questions to ask a roof cleaner
- What pressure and which products will you use, and are they safe for my tiles or steel?
- Have you checked whether any part of the roof is asbestos cement, and how?
- Where does the run-off go? I have a rainwater tank.
- How do you move around a tiled roof without cracking tiles?
- Are you treating the moss so it doesn't come straight back, and is that priced separately?
- Will you photograph the ridge and any broken tiles while you're up there?
Where we'd start
We'd hire someone who cleans gently, treats the moss and refuses to put pressure on anything that might be asbestos. On a steel roof near the beach, the most useful cleaning is often the part you can do from the ground with a hose: the eaves, the garage door head and the underside of the gutters, every few months.
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.