What grows on Adelaide roofs, and where
Shade and damp in the hills
The Adelaide Hills are generally a few degrees cooler than the plains and get noticeably more rain. Roofs under trees up there stay damp for longer after each shower, which is what moss and lichen need to take hold.
Frosty valleys
Frosts are common in the valleys of the Adelaide Hills and rare elsewhere in the city. A roof in one of those valleys can stay cold and wet well into a winter morning, and that's the kind of roof where growth builds up.
Old tiles on the plains
Cement and clay tiles were standard on Adelaide roofs until the 1970s. Tiles that old can be brittle, and the wrong cleaning method, or careless footwork, cracks them.
Long dry summers
On a sunny roof down on the plains, a long dry summer gives moss little to live on, so heavy growth is less common than in the Hills. Many plains roofs only need cleaning when they're about to be painted.
Never pressure clean asbestos cement
It's illegal in every state to use high-pressure water on asbestos materials. According to ASSEA, the asbestos safety agency, water-blasted asbestos roofs have contaminated neighbouring properties, footpaths and stormwater drains, and the clean-ups have run to hundreds of thousands of dollars. If your roof might be asbestos cement, get it tested before anyone touches it. Read is my roof asbestos?
How a roof should be cleaned
Tiles. Monier strongly advises against pressure washers on roof tiles because of the risk of damage, and recommends a professional roof cleaner. Ask how they'll lift moss without blasting the surface or forcing water up under the tiles. Some cleaners apply a moss treatment first. Ask for it as a separate line on the quote.
Colorbond. BlueScope's advice for older Colorbond is a wash with household detergent and water, using a mop or soft nylon broom, then a fresh-water rinse. It says never to use abrasive or solvent cleaners, and not to wash with hard bore water.
Moss on a tile roof is mostly a nuisance, not a structural problem, but it holds water and leaves where they shouldn't sit. Our moss and lichen removal page goes further.
Before you book a clean
- How will you clean my tiles without a high-pressure blast?
- Will you treat the moss first, and with what product?
- How will you keep runoff out of my rainwater tank and garden beds?
- Will you replace any tiles that crack while you're on the roof?
- If you think my roof could be asbestos cement, will you stop and tell me?
What you can do from the ground
You can
- Check for moss and lichen from the street or a window, with binoculars
- Trim back branches that shade the roof and drop leaves on it
- Keep gutters clear so the roof drains properly
Leave to a roofer
- Any cleaning that means being on the roof
- Moss treatments applied from the roof
- Anything on a roof that might contain asbestos
What we'd do
On the plains, we wouldn't pay to clean a roof on its own unless moss is genuinely building up. Fold the clean into a restoration or repaint instead. In the Hills, an occasional clean and moss treatment is worth it, and cutting back overhanging branches is the cheapest fix of the lot.
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.
Getting a quote
Send us your suburb and what's growing on the roof. We'll pass the job to one licence-checked roofer who works your area, where we have one, and tell you plainly when we don't. Our national roof cleaning page and the Adelaide hub cover more.