Drainage, surfaces and lawn
Patio cleaning: how to clean a patio without wrecking it
Patios go green and slippery as algae, moss and grime build up on damp, shaded paving. Most clean up well with a stiff brush, warm soapy water or a patio cleaner, and rinsing. A pressure washer works on robust paving but can erode jointing sand and damage soft natural stone, so match the method to the surface.
- Also known as
- paving cleaning, jet washing a patio
- Easily confused with
- efflorescence salts on new paving, permanent staining (rust, oil)
- How serious
- Low: cosmetic, but slippery algae is a slip hazard
- Typical cost
- Usually no cost for DIY control
How to identify patio cleaning
The usual culprits are a green or black film of algae and lichen making paving slippery, moss growing in the joints, and general grime. It is worst in shaded, damp areas and over winter.
Tell algae and dirt (which clean off) from permanent staining such as rust or oil and from white efflorescence salts on new slabs (which need a different approach), so you choose the right treatment.
How serious is it?
Low: cosmetic, but slippery algae is a slip hazard
Patio grime is cosmetic, but slippery algae is a genuine slip hazard, especially for older people and in winter, so there is a safety reason to keep paving clean.
The bigger risk is damaging the patio while cleaning it. Overusing a pressure washer can blast out jointing sand, pit soft stone and force water under slabs, turning a cleaning job into a repair.
How to fix it yourself
- Sweep off loose debris, then scrub with a stiff brush and warm water with washing-up liquid, or a dedicated patio cleaner for stubborn algae.
- For green algae and moss, a proprietary patio or path cleaner (or a diluted treatment per the label) loosens growth; rinse well afterwards.
- If using a pressure washer, use a lower pressure and a wide fan nozzle, keep the lance moving and not too close, and avoid soft natural stone and lime-pointed joints.
- Re-sand block paving or repoint joints afterwards if cleaning has washed the filling out.
- Improve drainage and reduce shade where you can, since damp shade is what lets algae and moss return.
When to call a professional
- The patio is large, made of delicate natural stone, or has stains (oil, rust) that resist normal cleaning.
- Cleaning has loosened slabs or washed out a lot of jointing that needs professional repointing.
Who to call
- A specialist patio or driveway cleaning firm experienced with your paving type.
- A landscaper or paving contractor for relaying, repointing or drainage improvements.
Frequently asked questions
What is the best way to clean a patio?
For most patios, sweep, then scrub with a stiff brush and warm soapy water or a patio cleaner, and rinse. This is gentler than a pressure washer and will not blast out jointing. Reserve pressure washing, at low pressure, for robust paving, and avoid soft natural stone.
Will a pressure washer damage my patio?
It can. High pressure erodes jointing sand, pits soft stone such as sandstone and limestone, and can force water under slabs. If you do use one, keep the pressure low, use a wide nozzle, keep the lance moving, and be ready to re-sand or repoint the joints afterwards.
How do I stop my patio going green?
Algae and moss thrive in damp shade, so improving drainage, reducing overhanging shade and keeping the patio swept all slow regrowth. A patio cleaner with a longer-lasting biocide effect helps, and regular light cleaning is easier than tackling heavy green build-up once a year.
Sources
Editor, HomesAndHedge
Oliver leads HomesAndHedge's editorial coverage of home and garden problems. He researches and writes the plain-English explainers on pests, invasive plants, damp and mould, drainage and wildlife, drawing on guidance from bodies such as the Property Care Association, the RHS and the NHS, and is clear about when a job needs a qualified professional.
Last reviewed: 8 June 2026