Pressure washing seems like the obvious way to clean a roof, and it is sometimes offered as a quick fix. In practice, blasting a roof with high-pressure water is risky, and many roofers avoid it.
What can go wrong
Concrete and clay tiles have a surface that protects them from the weather. A pressure washer can strip that surface away, leaving the tile rougher and more porous, so it holds moisture and attracts more moss. Water forced up under the tiles can soak the underlay and the loft, causing damp. High pressure can also crack old tiles or dislodge slates, and it can wash granules into gutters.
The safety side
Roofs are slippery, especially when wet, and a person standing on a wet moss-covered roof with a heavy hose is at risk of falling. Using a pressure washer from a ladder is dangerous. This is work best left to people with the right equipment.
A gentler method
Moss can be scraped and brushed off by hand, working carefully down the slope so the debris does not settle in the gutter. Afterwards, the roof is treated with a suitable biocide to kill remaining spores. The treatment takes time to work, so the roof gradually cleans itself over the following weeks and months.
Check the results
After cleaning, a roof should be checked for any damaged tiles or loose ridge bedding. Moss can hide those problems.
What about doing it yourself?
It is safest to avoid DIY roof cleaning. Moss is slippery and the risk of falling outweighs the saving.
See our Roof Moss Removal section or call 07766 547309.
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