Is that slate, or asbestos cement?
Asbestos cement 'slates' and shingles about 4 mm thick were made in Australia from the late 1800s to the 1980s, often to replace real slate while keeping the original look, and Ballarat has plenty of houses from that span. Only a NATA accredited laboratory test can confirm asbestos. It's illegal in every state to use high pressure water on asbestos materials, so nobody should clean, walk on or scrub a roof like that until it's been tested. Start with is my roof asbestos?.
Why Ballarat roofs grow moss
Fog, frost and a lot of wet days
The aerodrome records 620.9 mm of rain a year over 160.7 days, and widespread frost and fog are a regular sight. Roof faces that never get direct sun stay damp for days, which is all moss and lichen need.
Shade from the street trees
Mature avenues line nearly every gridded street in Soldiers Hill and Ballarat Central. The roofs under them get less sun and more leaf litter, and the litter holds moisture against the tiles.
Bushland around the edges
Around Black Hill, Brown Hill, Buninyong, Canadian and Mount Clear, bark and leaves collect in valleys and behind chimneys. Clearing that litter is part of the clean, and in a bushfire-prone area it's fire preparation too.
Old and brittle roofs
Victorian, Federation and Interwar houses in the old centre may still carry early tiles. NSW's heritage inspection schedule warns against walking on brittle roof tiles, so ask how the cleaner will move around the roof.
How a Ballarat roof should be cleaned
Monier, the tile maker, strongly advises against pressure washers on roof tiles because of the risk of damage, and recommends a professional roof cleaner. A softer wash and a moss treatment that kills growth at the root is the safer route on most tiled roofs.
Not every stain is moss. A whitish-grey film on concrete tiles can be efflorescence, natural salts rising to the surface, which Monier says doesn't affect performance and usually disappears on its own. No need to pay to blast it off.
Questions to ask a Ballarat roof cleaner
- What is my roof made of, and could any of it be asbestos cement?
- Will you use a soft wash and moss treatment, or high pressure, and why?
- How will you avoid cracking old or brittle tiles?
- Will you clear the valleys and flush the gutters afterwards?
- How long does your moss treatment usually keep regrowth down?
Where we'd start
On a house built before 1990 with a roof nobody has identified, we'd get the material tested before booking any clean. On a sound tiled roof under Ballarat's trees, we'd pay for a gentle clean and moss treatment rather than a pressure blast, and we'd trim back anything shading the roof. Our roof cleaning page explains the methods in more depth.
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.