A sandstone patio in Horsham, West Sussex that had developed black spot — the stubborn lichen-based staining that embeds itself into natural stone and can’t be removed by standard pressure washing alone. The customer had tried treating it themselves without success.
The problem: black spot lichen on natural sandstone
Black spot is a specific type of lichen that penetrates the surface of porous natural stone rather than just sitting on top of it. It appears as small dark circular spots that gradually spread and merge — on pale sandstone it’s particularly obvious. Standard pressure washing shifts the surface layer but leaves the lichen spores in the stone, so it comes back within weeks. Removing it properly requires chemical treatment followed by controlled pressure washing to lift the dead lichen fully out of the surface.
What we did
- Applied a specialist biocidal treatment to the affected sandstone to break down the lichen at root level
- Allowed dwell time for the treatment to penetrate the stone before washing
- Pressure-washed the full patio with a rotary surface cleaner to remove the treated lichen and all general algae and staining
- Left the surface clean with the black spot fully removed, not just suppressed
The result
The sandstone came back to a clean, even colour with no trace of the black spot. The whole patio — the main entertaining area and the surrounding path — looked completely different. The customer had been looking at the staining for two years; the right treatment approach sorted it in a single visit. With an annual biocide application going forward it shouldn’t return to the same extent.
Black spot removal and patio cleaning across Horsham and West Sussex
We treat and remove black spot lichen from natural stone patios across Horsham, Crawley and West Sussex. It’s a job that requires the right chemistry and technique — pressure washing alone won’t deal with it. If you’ve got persistent dark spots on sandstone, limestone or Indian stone that won’t shift, get in touch for a proper assessment.
