How-to
How to Clean a Patio Without Damaging It
8 min read · Updated August 2026
A dirty patio is one of those jobs that looks simple until you've done real damage to it. We see it a lot around Wokingham and Earley: someone hires a pressure washer for the weekend, goes in too close with too much pressure, and ends up etching the surface of their sandstone or blasting all the jointing sand out from between their block paving. The patio looks clean for a week, then the weeds come back worse than ever because the sand that was keeping them out is gone.
Cleaning a patio properly is less about brute force and more about matching the method to the material. Concrete flags, natural stone, block paving and porcelain all behave differently under pressure, and each has its own weak points - sealant, jointing compound, surface finish, or the stone itself. Get the technique wrong and you can end up spending more putting it right than you would have paid to have it done properly in the first place.
This guide runs through how to clean a patio safely, when jet washing is the right tool and when it isn't, and what to do afterwards to keep it looking good for longer. If you'd rather not risk it yourself, we cover driveway and patio jet washing across Wokingham, Earley, Arborfield, Spencers Wood, Sindlesham, Farley Hill, Bracknell and Winnersh - call 07769315849 for a quote.
Work out what your patio is actually made of
Before you touch a pressure washer, identify the material. Concrete block paving and standard concrete flags are tough and can generally take a reasonably high pressure. Natural stone such as sandstone, limestone or slate is softer and more porous, and aggressive pressure washing can strip the surface layer, leaving it rough, pale and prone to soaking up dirt faster than before. Porcelain paving is hard-wearing but the joints and any resin bonding around the edges can be damaged by careless use.
If you're not sure what you've got, do a small test patch in an inconspicuous corner first - behind a pot or under a step - before you commit to cleaning the whole area. This tells you how the surface reacts and lets you dial in the right pressure and nozzle before it matters.
Choose the right pressure and nozzle
A rotary or turbo nozzle concentrates pressure into a small, spinning point and strips grime fast, but it's also the nozzle most likely to etch soft stone or blast out sand. A fan nozzle spreads the pressure over a wider area and is gentler on the surface, which is usually the better starting point for anything other than heavily soiled concrete.
Keep the nozzle at least 20-30cm from the surface to start with, moving it further away if you see any marking, and always test on a small area first. Work in a consistent pattern - long, overlapping sweeps rather than lingering in one spot - so you don't create patchy 'tramlines' where some areas are cleaner than others.
When jet washing is the wrong tool
Sealed patios, painted surfaces, and anything with lime mortar pointing (common on older properties) can all be damaged by standard pressure washing. High pressure can strip sealant completely, meaning the patio will need resealing straight after, which adds cost. On lime mortar, aggressive jetting can erode the pointing and eventually let water in behind the joints.
In these cases, a soft washing approach - using a lower-pressure application of a cleaning solution that's left to dwell and lift dirt biologically rather than by force - is usually the safer option. It takes a bit longer to work but doesn't carry the same risk of surface damage. See our separate comparison of jet washing versus soft washing for more detail on which suits your patio.
Deal with weeds and moss properly, not just cosmetically
Blasting weeds out of the joints with a pressure washer gives instant satisfaction but doesn't solve the underlying problem - the roots and the growing conditions are usually left in place, and the weeds tend to come back within a few weeks. It's better to treat the joints with a suitable weedkiller a few days before cleaning, then jet wash the dead growth away afterwards.
Moss is a slightly different problem: it thrives on damp, shaded, north-facing patios and on surfaces where jointing sand has washed away, giving it something to root into. Cleaning removes the visible moss, but if the patio is chronically damp and shaded you'll likely see it return within a season or two. Improving drainage and cutting back overhanging vegetation helps more than repeated cleaning.
Re-sand and re-point after cleaning block paving
If you've got block paving, expect the cleaning process to strip out some or all of the kiln-dried sand between the blocks, especially if you've used a rotary nozzle. This isn't just cosmetic - that sand locks the blocks together and stops them shifting under weight, and it also helps keep weeds from establishing. Leaving the joints empty after cleaning is one of the most common mistakes we see.
Once the surface is completely dry, brush kiln-dried sand into the joints and compact it in (a vibrating plate compactor for large areas, or firm brushing and light watering for smaller ones). Skipping this step means the paving will loosen over time and weeds will re-establish within weeks.
Sealing after cleaning: worth it or not?
Sealant isn't essential on every patio, but on natural stone and block paving it does two useful things: it makes future cleaning easier because dirt sits on the surface rather than soaking in, and it helps lock jointing sand in place. If your patio was previously sealed, it's worth resealing after a deep clean, because the cleaning process will have worn away some of the existing coating.
If your patio has never been sealed, it's a judgement call based on how much maintenance you want to do. A sealed patio needs less frequent cleaning but the sealant itself needs reapplying every few years. An unsealed patio is lower-maintenance in the sense that there's nothing to reapply, but it will pick up dirt and moss more readily.
How often should you clean a patio?
Most patios in this part of Berkshire benefit from a proper clean once a year, typically in spring after the worst of the winter grime, moss and algae have built up, or in autumn before leaf fall makes things worse. Shaded, north-facing patios under trees may need attention twice a year because they stay damp for longer and grow algae faster.
Light maintenance in between - sweeping off leaves, brushing away moss as it appears, and treating weeds early - reduces how aggressive the annual clean needs to be, which in turn reduces wear on the surface.
Typical costs for professional patio cleaning
| Patio size | Jet washing only | Jet wash + re-sand | Jet wash + seal |
|---|---|---|---|
| Small (up to 20m²) | £90 - £150 | £130 - £200 | £180 - £280 |
| Medium (20-40m²) | £150 - £240 | £200 - £320 | £280 - £420 |
| Large (40m²+) | £240 - £400+ | £320 - £500+ | £420 - £650+ |
When to call in a professional
If your patio is sealed, made of natural stone, has extensive moss or algae, or you simply don't want the hassle of hiring and returning equipment, it's usually worth getting a professional in. A competent operator will know how to read the surface, choose the right pressure and nozzle, and finish the job with re-sanding or sealing where needed - all of which reduces the risk of the kind of damage that's expensive to fix.
We cover patio and driveway jet washing across Wokingham, Earley, Arborfield, Spencers Wood, Sindlesham, Farley Hill, Bracknell and Winnersh. If you'd like a no-obligation quote, call 07769315849.
Frequently asked questions
- Can I use a domestic pressure washer on a patio?
- Yes, in most cases, but keep the pressure moderate and use a fan nozzle rather than a rotary/turbo nozzle on natural stone or older jointing, and always test a small area first.
- Why does my patio go green again so quickly after cleaning?
- Usually because the underlying cause - damp, shade, or loss of jointing sand - hasn't been addressed. Cleaning removes the moss but not the conditions that let it grow back.
- Should I seal my patio after jet washing?
- If it was sealed before, yes, because cleaning wears the coating down. If it's never been sealed, it's optional, but it does make future cleaning easier.
- Will jet washing damage block paving?
- It can strip out the jointing sand, which needs replacing afterwards. The paving itself is usually fine at moderate pressure, but the joints need attention.
- How much does professional patio cleaning cost?
- Typically £90-£400+ depending on size and whether re-sanding or sealing is included - see the cost table above for indicative ranges.