Moss, algae and dirt build up on paving over time, especially in shady corners and after a wet winter. As well as looking tired, green growth makes paths and steps slippery. Here is how to get it clean without causing damage.
1. Clear and sweep
Move furniture and pots, then sweep away loose leaves, soil and debris. A stiff brush or weeding tool gets moss and weeds out of the joints.
2. Check the surface
Different materials need different treatment:
- Block paving and concrete are hard-wearing and can usually be pressure washed.
- Natural stone, such as sandstone and limestone, is softer and can be marked by high pressure or damaged by acidic cleaners.
- Resin-bound surfaces and older, worn slabs need a gentler approach.
- Tarmac can be softened by very hot water or damaged by solvents.
If you are not sure what you have, test any method on a small, hidden area first.
3. Wash
A pressure washer is the quickest option on hard surfaces. Keep the lance moving, hold it at a low angle rather than pointing straight down, and work away from the house so dirty water runs off the paving. A rotary surface cleaner attachment gives a more even finish and less splashing.
On softer or delicate surfaces, a stiff brush with warm water and a cleaner suited to the material is safer.
4. Deal with stubborn marks
- Black spots on paving are often lichen. They are firmly attached and often do not come off with water alone.
- Oil stains that have soaked into porous paving may lighten but not disappear completely.
- Rust marks usually need a specialist cleaner suited to the stone.
5. Re-sand block paving joints
Pressure washing washes sand out of the joints between blocks. Once the surface is dry, brush kiln-dried sand into the joints to keep the blocks locked together and make it harder for weeds to take hold.
Look after the drains
Where you wash the dirt matters:
- Surface water drains in many areas lead straight to streams and rivers rather than a treatment works, so avoid washing detergents and chemicals into gullies.
- Silt and moss washed into a channel drain or gully can block it. Clear the grating afterwards.
- If water already pools on the driveway, a gully may be blocked. See why water pools on driveways.
Staying safe
Pressure washers can cause injury, so wear sturdy footwear and eye protection, and never point the lance at people, pets, windows or electrical fittings. Take care on steps and slopes, which become slippery when wet.
When to get help
A professional clean is worth considering for large areas, heavily stained paving, steep or awkward areas, or if you do not want to risk damaging the surface. Find out about our driveway and patio cleaning service, which can include clearing blocked gullies and channel drains at the same visit.