How to Remove Black Spots from a Patio (Lichen Explained)
Quick answer: How to Remove Black Spots from a Patio
Black spots on patios are lichen, which roots into the stone, so pressure washing alone will not remove them. The fix is a dedicated black spot remover or professional soft wash biocide, left to work and then rinsed. Spots fade over days to weeks, and the patio should then be sealed to slow them returning.
Key takeaways on how to remove black spots from a patio
- Black spot is lichen growing into the stone surface, not surface dirt.
- High pressure on sandstone can etch the surface and make it worse.
- Biocide treatments kill lichen; rain then gradually washes it away.
- Shade and damp encourage black spot, so cutting back overhanging trees helps.
What are black spots on a patio?
Those small, round black marks are lichen, a mix of fungus and algae. It anchors itself into porous stone such as Indian sandstone and limestone. That is why it survives jet washing and why it keeps coming back if it is not killed at the root.
How to remove black spot
- Sweep the patio and remove any moss.
- Apply a stone-safe black spot remover or a professional soft wash biocide.
- Leave it to work. Most treatments take from a few hours to several days.
- Rinse at low pressure.
- Repeat on stubborn areas, then seal the stone once it is fully dry.
Stopping black spot coming back
Lichen thrives in shaded, damp corners. Improving light and airflow makes a real difference. If large trees overshadow the patio, a tree removal specialist can advise on crown thinning or removal.
How to Remove Black Spots from a Patio: frequently asked questions
Does bleach remove black spots on patios?
Bleach can lighten the marks but it rarely kills lichen at the root and can discolour natural stone and harm plants. A dedicated treatment is safer and more effective.
Will a pressure washer remove black spot?
Usually not. It removes surface dirt but not the lichen rooted in the stone, and high pressure can damage sandstone.
How long does black spot remover take to work?
Anything from a few hours to a few weeks depending on the product and how established the lichen is.