Professional Patio Cleaning
That Restores the Original Stone
London & Surrey

Professional patio cleaning is the controlled removal of algae, moss, lichen, black spot, organic staining and ground-in dirt from paved outdoor surfaces using industrial equipment and targeted cleaning solutions. The goal is to restore the surface to its original colour and texture without damaging the stone, concrete or grouting.

If your patio slabs have turned black, green or patchy — or if the surface is slippery after rain — it needs professional cleaning. The discolouration is caused by a combination of algae, atmospheric pollution and organic acids from leaf litter, which penetrate the porous surface of most patio materials over time.

Natural stone patios (Indian sandstone, limestone, slate, granite) are particularly susceptible to staining because of their porosity. Concrete and porcelain slabs are more resistant but still accumulate surface algae and black spot lichen that cannot be removed with domestic cleaning products.

We clean all patio types and adapt our methods to the specific material. The pressure, chemical treatment and joint re-sanding approach is different for every stone type — one-size-fits-all cleaning damages surfaces and produces poor results.

Algae growth on patios creates a persistent slip hazard that worsens in wet weather. The biofilm is almost invisible when dry but becomes extremely slippery after rain or morning dew. Falls on patio surfaces are a leading cause of domestic injury, particularly for older residents.

Black spot lichen — the small, dark circular marks that appear on natural stone — is a particularly stubborn organism. It bonds with the stone at a cellular level and cannot be removed by pressure washing alone. Without targeted chemical treatment, it continues to spread across the surface, permanently staining the stone if left for several years.

Moss growing in patio joints breaks down pointing mortar and polymeric sand, destabilising slabs and creating gaps where water penetrates the sub-base. This leads to slab rocking, settlement and — in cold weather — frost heave where trapped water freezes and lifts slabs from their bed.

Weeds exploit weakened joints, pushing roots deep into the sub-base and widening gaps between slabs. Once established, weed roots are extremely difficult to remove completely, and regrowth is rapid unless the joints are properly restored.

The cost to re-lay a patio in London ranges from £2,000 to £6,000 depending on the area and material. Regular professional cleaning keeps your existing patio performing and looking good for its full lifespan.

Restores Original Colour

Years of staining stripped back to reveal the original stone colour and texture. The transformation is immediate and dramatic.

Eliminates Slip Hazards

All algae and biofilm completely removed, making your patio safe to walk on in all weather conditions.

Stabilises Loose Slabs

Joint re-sanding restores stability, preventing slab rocking and water penetration into the sub-base.

Removes Black Spot Lichen

Specialist chemical treatment removes black spot that pressure washing alone cannot shift — restoring clean, unmarked stone.

Prevents Weed Regrowth

Clean, properly filled joints with optional polymeric sand dramatically reduce weed establishment between slabs.

Protects Your Investment

Regular cleaning extends patio lifespan by decades, avoiding the £2,000–£6,000 cost of replacement.

Indian sandstone is the most popular natural stone patio material in the UK. It is porous, absorbent and available in a range of colours from buff and grey to red and brown. Professional cleaning requires moderate pressure (1,500–2,500 PSI) with a fan nozzle and alkaline cleaning solution. Acidic cleaners must never be used on sandstone as they dissolve the calcite within the stone, causing permanent surface damage and colour change.

Limestone is softer and more porous than sandstone, requiring lower pressures and even greater care with chemical selection. It stains easily and is particularly susceptible to acid damage — even mild acids like citric acid or vinegar can etch the surface. We use specialist limestone-safe cleaning solutions and operate at reduced pressure with wider spray patterns.

Porcelain patio tiles are non-porous and extremely hard-wearing, but their smooth surface means algae sits on top rather than within the material. This makes cleaning faster and results more dramatic. We can use higher pressures on porcelain without risk, and the tiles rarely require sealing as their non-porous surface naturally resists staining.

Concrete slabs are the most robust patio material and tolerate higher pressures, but prolonged or focused pressure can still etch the surface. We use surface cleaners for even coverage and apply alkaline degreasing solutions to remove the characteristic black organic staining that concrete develops in shaded, damp areas.

Granite setts and cobbles are extremely hard and tolerant of high pressure, but the irregular surface traps dirt in crevices that lance-only cleaning misses. We combine pressure washing with stiff brush agitation to clean every surface facet, particularly in the gaps between setts where moss accumulates.

Joint treatment after cleaning is critical for long-term results. Kiln-dried sand is the standard re-filling option — it is inexpensive and effective but needs periodic topping up. Polymeric sand is a premium option that hardens when wet, creating a semi-rigid joint that resists weed growth, insect penetration and erosion. We recommend polymeric sand for patios with chronic weed problems.

Post-clean sealing is available for all stone types. Penetrating sealants protect against staining without changing the surface appearance. Colour-enhancing sealants darken the stone slightly, bringing out the natural colour — popular on sandstone where the original warm tones have faded under staining.

Common Questions

Frequently Asked Questions