Patio care · Black spot lichen
How to remove black spot lichen from a patio
The direct answer: pressure washing on its own will never remove black spot lichen. It needs a specialist biocide dwell treatment that kills the lichen at the root, followed by several weeks for the dead spots to fade naturally. Power Wash Pro treats black spot as standard on every patio clean across Oxfordshire & Bucks.
Black spot lichen shows up as small, hard, tar-like dark patches — often mistaken for oil stains or ingrained dirt. It's actually a slow-growing organism that bonds into the microscopic pores of sandstone, concrete and some porcelain, which is exactly why a pressure washer can't lift it out. High pressure just cleans around the spots, or — worse — erodes the surrounding stone trying to chase it.
The only reliable fix is a biocide treatment applied directly to the affected areas, left to dwell and absorb into the lichen, then allowed to work over time. It's a chemical kill, not a mechanical scrub. Once the lichen is dead, weathering — rain, UV and foot traffic — gradually breaks the dead spots down and they fade from black to grey to barely visible, usually within two to six weeks. There's no product on the market that removes black spot instantly; anyone promising that isn't being straight with you.
Because it takes time, we always explain this before starting work: the patio will look dramatically better on the day of the clean, with the black spot noticeably fading over the following weeks as the treatment continues to work.
What actually works
The three-step process we use.
- A full pressure or soft wash first, to lift general dirt, algae and moss and reveal the true extent of the black spot.
- A targeted biocide treatment applied to affected areas, dwelled for the correct time to penetrate the stone.
- A patio-wide post-treatment to slow regrowth of algae and lichen together, so the whole surface stays cleaner for longer.
Get black spot treated properly, first time
Send a couple of photos of the affected patio and we'll tell you honestly what to expect — including realistic timescales — with a fixed quote back within 24 hours.
Frequently asked questions
Can I just pressure wash black spot lichen off my patio?
No — pressure alone won't shift it. Black spot lichen bonds chemically into the surface of sandstone and concrete, so blasting it just polishes around the spots or damages the stone without removing them. It needs a biocide treatment that kills the organism at the root.
How long does it take for black spot to disappear after treatment?
Once we apply a specialist biocide, the black spots don't vanish overnight — they gradually fade as rain and UV break down the dead lichen over 2–6 weeks. Stubborn or long-established patches can take a little longer.
Why does black spot keep coming back?
Lichen spores are airborne and thrive on damp, shaded, north-facing paving. A one-off treatment kills what's there, but a periodic maintenance clean and post-treatment every 12–24 months stops it re-establishing.
Does black spot treatment damage the patio or plants nearby?
Used correctly, no. We apply biocide carefully, avoid run-off onto borders and lawns where possible, and use products safe for sandstone, limestone, porcelain and concrete once diluted and applied to specification.
Is black spot lichen removal included in a standard patio clean?
Yes — every patio clean from Power Wash Pro includes a biocide post-treatment as standard, which tackles algae, moss and black spot together rather than as a separate paid extra.