Low-pressure roof cleaning is the safe alternative to blasting a roof with a pressure washer. It uses a controlled low-pressure wash — hot or cold, depending on the tile type and the level of growth — to lift away moss and dirt without eroding the tile surface, followed by a targeted biocidal softwash that kills the remaining lichen and fungal spores at the root.
Why pressure washing is the wrong approach
It's tempting to think a powerful pressure washer will blast moss away in seconds. It will — but it will also:
- Strip the protective granular coating from concrete tiles, making them porous
- Force water under tiles and into the felt membrane beneath
- Dislodge ridge tiles and pointing
- Spread moss spores across your driveway and gutters, where they'll regrow
High-pressure jet washing is the fastest route to an expensive re-roof. The right approach is far gentler.
How the low-pressure method works
At Clearstone, we clean roofs in three careful stages:
- Manual moss clearance. We carefully remove the heavy moss build-up by hand and with soft tools, working from scaffolding or roof crawling ladders to minimise foot pressure on fragile clay or concrete tiles.
- Low-pressure rinse. A controlled wash lifts the remaining algae and staining without forcing water where it shouldn't go.
- Biocidal softwash. A biocidal solution is applied to kill algae, lichen and fungal spores at the root — not just the visible growth on the surface. This is what keeps the roof cleaner for far longer.
Because the treatment kills growth at the root rather than just blasting off the top, the roof stays cleaner for years rather than months.
Which roofs can be cleaned this way?
Most concrete interlocking tiles, clay tiles and slate roofs can be cleaned safely with the low-pressure method. Older or more fragile roofs — particularly very old clay peg tiles — need extra care, and sometimes a biocidal-only treatment (no mechanical clearance) is the safer choice.
If you're unsure, the best first step is a free roof inspection. We'll assess the tile type, the level of growth, and whether cleaning is safe — and we'll tell you honestly if it isn't.
Watch the short answer
In this short video, we explain what low-pressure roof cleaning actually means and why it protects your tiles.
Related questions
Get your free roof cleaning quote or call us on 01747 413013.
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