By Tom, TMF Exterior Cleaning ·
If your patio is covered in small black dots or pale, crusty circles that don't budge no matter how hard you scrub, you're not alone. They're some of the most common problems we see on patios across Norfolk and Suffolk — especially on Indian sandstone and natural stone.
What is black spot?
Black spot is a type of lichen: a combination of fungus and algae that grows together. It roots itself into the pores of the stone and forms small black dots, which slowly spread and join up. It's especially common on sandstone and other natural stone patios.
What are the white circles?
Those pale grey or white circular patches — you can see plenty of them in the before photo on our patio cleaning page — are lichen too. They grow slowly outward in rings and bond firmly to the surface.
Why won't a pressure washer remove it?
Because lichen is anchored into the stone rather than sitting on top of it. A pressure washer will remove the dirt, moss and algae around it, but the lichen itself usually stays put. Turning the pressure up to try and blast it off risks damaging the surface of the stone and the joints.
How black spot and lichen are removed
The answer is treatment rather than force. After a thorough clean, a specialist treatment is applied to the paving. It kills the lichen and breaks down its hold on the stone. Some spots fade immediately; others continue to lighten over the following weeks as rain and weather do the rest.
Can you stop it coming back?
Lichen and black spot spores are everywhere outdoors, so no patio stays clean forever. Keeping the patio swept, cutting back overhanging plants to let in light, and having a periodic clean and treatment all help keep it under control. Shaded, damp patios will need attention more often than open, sunny ones.
The result
A properly cleaned and treated patio often looks dramatically different — the warm browns, reds and golds of sandstone come back through. Want to see what yours could look like? Send us a photo and we'll give you a quote.
Related services
Patio & Decking Cleaning
Sandstone, slabs and decking deep-cleaned, black spot and lichen treated, and patios repointed where the joints have gone.
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Block paving, tarmac, concrete and resin driveways cleaned, weeds and moss removed, joints re-sanded and the surface resealed.
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