What builds up on a Townsville roof
Damp air in the wet
Afternoon humidity at Townsville Airport averages 57% across the year and peaks at 68% in February. Mould and lichen like damp, shaded spots, so the south side of a roof and anywhere under trees usually go green first.
Salt off the water
Homes along the Strand, and across Magnetic Island's settlements from Arcadia to West Point, sit close to salt water. Rain washes most of a roof, but BlueScope warns that sheltered spots it can't reach, like under eaves, need hosing to stop salt sitting on the steel.
The dry season is cleaning season
Townsville's winters are mostly fine, dominated by south-east trade winds. That's when a roof dries quickly after cleaning and a roofer can see the surface properly, before the wet returns in November.
How each roof should be cleaned
Concrete and terracotta tiles. Monier strongly advises against pressure washers on roof tiles because they can damage them, and recommends a professional roof cleaner. Moss and lichen grow more on unglazed terracotta, but Monier says it only sits on the surface. See our guide to moss and lichen removal.
Colorbond and Zincalume. BlueScope says never to use abrasive or solvent cleaners such as turpentine, kerosene or thinners on prepainted steel, and not to wash with hard bore water. Sugar soap shouldn't go on bare Zincalume. A soft broom, mild detergent and fresh water is the usual approach.
Rust stains on newer metal roofs can come from swarf, the metal filings left after cutting and drilling. BlueScope says installers should sweep it off daily. If you see little rust spots after solar or a new skylight goes in, that's often why.
Old fibro roofs: don't clean them
In Queensland it's illegal to use a high pressure water blaster on an asbestos cement roof. Homeowners can be fined up to $10,000 and pay the clean-up. If your house was built before 1990 and the roof is grey sheeting rather than metal or tile, get it tested first. The state's asbestos site suggests a fungicide and sealant instead of cleaning. Never walk on it: Safe Work Australia treats asbestos sheeting as likely to be fragile.
Questions to ask a roof cleaner
- What method will you use on my roof type, and what pressure?
- What chemicals, and are they safe for my tank water and garden?
- Is my roof asbestos, and if you're not sure, will you get it tested first?
- Will you send photos of any cracked tiles, rust or loose screws you find?
- Do you have public liability insurance?
What we'd do
We'd book a gentle clean in the dry months and treat it as a free inspection: ask for photos of anything broken, rusted or loose. If the roof is metal and near the water, hose the sheltered spots yourself from the ground between cleans. Skip any cleaner who wants to blast an old grey roof.
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 your suburb and what the roof is made of, and we'll pass your job to one local roofer who does cleaning there, where we have one. Our national roof cleaning page and the Townsville hub have more.