Start with sweeping and a suitable patio cleaner, test a small area, and use the lowest effective pressure. Keep the jet away from weak pointing and soft stone. If joints are loose or slabs move, repair those defects before aggressive cleaning.
Check the surface before you start
Cleaning will not fix loose slabs, crumbling pointing or poor drainage. Walk the area first and note any rocking paving, open joints, broken edges and places where water collects. These areas need gentler treatment and may require repair before a full clean.
Use the least aggressive method that works
- Remove furniture and sweep away loose debris.
- Treat weeds and organic growth using a product suitable for the paving material.
- Test an inconspicuous area.
- If pressure washing, begin on a lower setting with a wider fan.
- Keep a consistent distance and avoid directing the jet into joints.
- Allow the surface to dry before deciding whether another treatment is needed.
Why pressure washing can cause damage
A narrow, powerful jet can strip loose mortar from joints, mark softer sandstone, remove protective sealers and drive water where it is not wanted. Block paving may need jointing sand replaced after cleaning. Timber decking needs a different, gentler approach to avoid raising or splintering the grain.
Moss, algae and black spots
Green growth often returns where a patio stays damp or shaded. Cleaning improves the surface, but drainage, overhanging plants and air movement also affect how quickly growth comes back. Black lichen spots can need a suitable treatment and patience rather than ever-higher pressure.
After cleaning the patio
Once the paving is fully dry, check whether joints have been loosened or washed out and whether water still falls towards drains and away from the building. Block paving may need suitable jointing sand replaced. Mortared joints should be repaired with a compatible material rather than filled while they are still wet or loose.
Avoid sealing simply because a surface looks cleaner. Some stone and paving systems need to breathe, and the wrong sealer can change colour or trap moisture. Check the paving manufacturer’s guidance before applying any coating.
Common questions
Can pressure washing remove patio pointing?
Yes. Weak, cracked or sandy joints can be stripped out by a concentrated jet. Inspect and repair defective pointing rather than relying on careful aim alone.
Can I use bleach on a patio?
Strong or unsuitable chemicals can damage surfaces, plants and drainage systems. Use a product intended for the paving material and follow the manufacturer’s instructions.
Why is my patio still patchy after cleaning?
Different slabs weather at different rates, and stains can sit within porous stone. Let the surface dry fully before judging the result or applying another treatment.
Further guidance: Marshalls guidance on pressure washing patios and decking.