Best overall for Canberra roofs in 2026: soft washing. Best for heavy moss on concrete tile: high-pressure washing, used with caution. Best budget option: DIY zinc or chlorine spray. Best for heritage terracotta: steam. Best for one stubborn patch: manual scraping.
Soft washing kills moss spores without cracking most tile and Colorbond
High pressure strips moss fastest and can crack old concrete tile or void a coating warranty
Steam suits heritage terracotta where chemical run-off is tight
DIY spray is cheapest and does not physically remove buildup — it waits on rain
Scraping is for one patch, not a whole roof
Why this matters
Canberra frost and shaded southern pitches hold moisture. That is what moss and lichen want. The wrong method can crack old terracotta, strip Colorbond, or send run-off into stormwater.
Clear Jet is on roofs across the ACT every week. Pressure or soft wash is not “whatever gear is on the truck.” It is material, age, and how bad the growth is.
What a method has to clear
Material — terracotta, concrete tile, Colorbond
Run-off into ACT drains and garden beds
Spores vs only the visible layer
Cracked tiles, stripped glaze, lifted coatings
How long before it comes back
Time to do the whole roof
At a glance
Soft washing — tile and Colorbond with algae or lichen. Kills spores, low pressure. Result builds over a day or two.
High-pressure washing — heavy moss on concrete tile. Fastest strip. Can crack tiles or strip a coating.
Steam — heritage terracotta, chemical-restricted sites. No chemical run-off. Slower. Fewer operators.
DIY zinc or chlorine spray — light stain, tight budget. Cheapest. No physical removal. Rain-dependent. Run-off risk.
Manual scraping — one or two patches. No gear cost. Labour, fall risk, spores stay.
1. Soft washing — default for tile and Colorbond
Low pressure plus a biodegradable treatment that kills moss, lichen and black algae at the root. That is what Clear Jet uses on most Canberra houses. Aged terracotta and painted Colorbond keep their coating.
Pros: no crack risk on aged tile, slower regrowth, Colorbond warranties stay intact, gentler on gutters and beds.
Cons: not instant, needs a retreatment cycle, less “wow” than a blast.
Best for: homeowners who want the growth gone without gambling the roof.
2. High-pressure washing — heavy moss, newer concrete tile
A strong jet strips the mat off. Fastest visual change. Not for every roof.
Pros: instant, thick moss, newer concrete tile that is rated for it.
Cons: cracks old or heritage terracotta, strips paint and glaze, does not kill spores so it often returns faster.
Skip on terracotta and heritage. Confirm the material before anyone books a blast.
3. Steam — heritage terracotta
High-temp steam instead of chemicals and high pressure. Niche in Canberra. Right when the listing or the run-off rules say no chemistry.
Pros: no chemical run-off, gentle on old terracotta.
Cons: slow across a full roof, weaker on thick mats, fewer ACT operators.
If a cleaner reaches for a pressure washer before asking what the tiles are, that is the wrong call on terracotta.
4. DIY spray — light stain only
Dilute zinc or chlorine, leave it, wait for rain. Fine for a light film. Useless on established moss.
Pros: cheapest, no hire.
Cons: no physical removal, rain decides it, beds and drains take the run-off, weeks to show.
5. Scraping — one patch
Hand or a soft brush. No gear. Does not scale.
Pros: precise, no chemical or water hit.
Cons: slow, fall risk without a harness, spores stay.
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https://www.clearjet.com.au/#quote
Which to pick
Most Canberra tile and Colorbond: soft wash. Heritage terracotta with run-off limits: steam. One small patch: scrape. Newer concrete tile with a heavy mat: high pressure only after the material is confirmed.
FAQ
Best method in 2026?
Soft washing for most tile and Colorbond.
Is high pressure bad for tiles?
It can crack old terracotta and strip Colorbond. Newer concrete tile only, and only if it is rated for it.
How much does professional roof cleaning cost?
Size, pitch and how bad the growth is. Quote first — no flat rate here.
How often?
South pitches stay wet and grow faster. A soft-wash cycle lasts longer than one blast.
Safe on Colorbond?
Soft wash yes. High pressure can strip the factory coat.
Can I DIY?
Light stain, spray. Established moss plus a ladder is a fall risk.
Stormwater?
Untreated spray and blast water can enter drains. Soft wash and steam are gentler.
Soft wash vs pressure?
Soft wash = low pressure + spore kill. Pressure = water only. Soft wash is gentler and lasts longer. Pressure is faster and riskier on old roofs.
One last thing
The shaded side — usually south in Canberra — comes back first, whatever method you used. If the quote does not mention aspect, ask before the work is booked.
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https://www.clearjet.com.au/#quote
