Lichen is the crusty grey, white or orange growth that looks painted onto tile, coping stones and old slate. Unlike algae it bonds physically to the surface, so it does not rinse off and scraping alone tends to take the surface with it.
Why it grips so hard
Lichen roots into microscopic pores. On weathered concrete tile and soft limestone copings those pores are wide open, which is why the same roof can be clear on the sheltered side and crusted on the exposed one.
This guide sits under our Roof Cleaning work, covering 20-mile radius of Plymouth.
Treatment over force
We treat lichen with a dwell-time biocide and let the weather do the last part of the work. Two visits are sometimes more honest than one aggressive one, and we say so at quoting stage.
Expect a staged finish
After treatment, lichen greys off, loosens and weathers away over following weeks rather than vanishing the same afternoon. Anyone promising an instant lichen-free roof is jetting it.
Questions we get on this
- Will the roof look clean on the day?
- Better, but not finished. Lichen releases over the weeks after treatment - that gradual result is the sign it was done properly.
- Is lichen a sign of a failing roof?
- Not by itself. It is a sign of a damp, exposed surface. We flag anything structural we can see while we are up there.
- Can you treat stone copings too?
- Yes, and they often need it more than the tiles, because water sitting on a coping feeds growth into the wall below.
Related reading
- Chimneys, ridges and the growth nobody can see
- Bungalows: low roofs, long gutters and big driveways
- Garages, sheds and outbuildings
- What changes the price of a roof clean