Patio Pressure Washing

A grimy patio is the silent garden killer. Even the prettiest planting and the smartest furniture struggle to compete with slabs that have turned grey-green with algae or are streaked with the inky black spots that natural sandstone is famous for. The good news is that very few patios are actually beyond saving — they just need the right approach. We pressure wash patios across the North East every working day, and a properly cleaned patio looks so transformed that homeowners regularly tell us they've fallen back in love with their garden.

Whether you've got Indian sandstone, riven slabs, granite setts, porcelain pavers or old-school concrete flags, we'll match the technique to the material so you get a deep clean without surface damage.

Patio surfaces we clean

Patio materials behave very differently under pressure. Indian sandstone, for example, is porous and stains easily but can take a fairly aggressive clean if done with the right nozzle. Porcelain, by contrast, is almost stain-proof but is laid with vulnerable joints. Concrete flags are tough but easy to "tiger stripe" if you use a focused lance. Choosing the wrong technique is exactly how patios get permanently scarred.

• Indian sandstone — both sawn and riven. Cleaned with a rotary surface cleaner and biocide pre-treatment to lift the famous black spots.
• Yorkshire and natural stone flags — gentler pressure, longer dwell time, careful joint protection.
• Porcelain pavers — surface is bullet-proof but joints aren't. We focus pressure on the slabs, not the gaps.
• Granite setts and slabs — exceptionally tough; takes a proper deep clean.
• Concrete flags and bradstone — even pressure with a flat-surface cleaner to prevent striping.
• Block paving patios — same approach as block driveways, with re-sanding included.
• Slate patios — soft-wash where possible to avoid flaking.

What black spot is and why ordinary cleaners can't shift it

If you've got Indian sandstone in particular, you'll be familiar with black spots — small, tar-like, raised dots that appear after a couple of years. They aren't dirt and they aren't moss; they're a lichen called Verrucaria nigrescens that fixes itself into the stone with a chemical bond. Domestic washers can rinse them but won't kill the root structure underneath, which is why they always come back within months.

We tackle black spot in two stages. First we apply a specialist biocide and let it dwell, which kills the lichen at the root. Then we use a rotary surface cleaner at higher pressure to physically lift the dead spots out of the stone. Done properly, the spots come out and stay out for years.

Joint sand and re-sanding

On any patio with sand-filled joints — block paving, certain natural stone installations and most flagged patios with thin pointing — pressure washing will inevitably wash some of the joint material out. That's not damage, it's expected, and any decent contractor allows for it. We brush in fresh kiln-dried sand at the end of every block paving clean, and on flagged patios we can quote separately for re-pointing if the existing pointing is failing.

Re-sanding does two important things. It locks the slabs back together so they don't rock, and it dramatically slows the return of weeds. A patio that's been cleaned but not re-sanded will look great for a few weeks but start sprouting weeds in the joints within months. Re-sanding properly buys you years.

Sealing patios

Sealing a patio after cleaning is optional but very worthwhile, especially on porous stone like Indian sandstone or limestone. A good penetrating sealer will resist staining from food, drink, BBQ fat and rusty furniture; it'll repel water (so weeds get less of a foothold); and it'll slow the regreening of the stone. Some sealers also give the slabs a low-sheen wet-look finish, which makes the colours far richer.

We use breathable, micro-porous sealers wherever possible — these protect the stone without trapping moisture underneath, which is what causes flaking and white blooming. We always seal a stone-dry patio (typically the day after a clean if the weather's good) and we'll never seal in dirt.

Why DIY pressure washing rarely cuts it

Plenty of customers call us after attempting a DIY clean. The most common issues are tiger striping (uneven bands across slabs caused by an unsteady lance), blown joints (sand washed clean out and not replaced), and partial cleans where the lichen comes straight back two months later. Domestic machines also lack the flow rate to clear away the slurry that proper cleaning produces, which is why DIY patios often look worse a week after washing as the dirty water dries back into the stone.

Our hot-water petrol washers run at high enough pressure and flow to lift dirt and rinse it away in one pass. We use rotary surface cleaners that distribute the pressure evenly. And we re-sand and tidy up at the end so the patio is finished, not just washed.