Removing moss from the roof: why it's more involved than you think

Moss on roof tiles constantly retains moisture. That moisture penetrates the porous tile structure and causes cracks during temperature fluctuations and frost.

Removing moss with a pressure washer is wrong: the force damages the protective layer of tiles, making them even more porous.

The correct method is a gentle chemical treatment with a biocide. This kills the moss and spores — after a few weeks it naturally falls off with rain.

After treatment, it's advisable to apply a hydrophobic protective coating that repels moss and algae for up to 5 years.

When is professional help needed? If the roof is hard to access, if more than 20% of tiles are affected, or if you have doubts about the ridge or underlay.

Prevention is cheaper than repair: a treatment every 3–5 years costs a fraction of tile repair or replacement.