Stone Pressure Washing

Natural stone has a presence that no manufactured material can match — but it's also one of the most variable surfaces to clean. Sandstone is porous and prone to black spotting; limestone is soft and damaged easily; granite is hard but its joints aren't; slate flakes if abused. Cleaning natural stone properly takes experience and the right equipment, and that's where we come in.

We clean every kind of natural stone you'll find in a North East property — patios, walls, paving, steps, statuary, garden features and stone facades on heritage buildings. Our approach is always to start gentle and only step up the intensity if the stone can take it.

Stone types we work on

• Indian sandstone — the most common stone patio in modern UK gardens. Porous, prone to black spotting, but cleans up beautifully.
• Yorkshire stone — denser than Indian sandstone, often quite weathered, takes a careful clean.
• Limestone — including Travertine and Portland. Soft, can be acid-damaged, needs gentle handling.
• Granite — extremely tough, takes a deep clean.
• Slate — riven slate is robust, polished slate is delicate. Soft-wash where possible.
• Reconstituted/cast stone — concrete-based, treated as concrete.
• Cobbles and setts — granite, sandstone, basalt.
• Stone walls and facades — including ashlar, rubble and dressed stone.

The challenges of stone cleaning

Natural stone has its own character and its own weaknesses. Sandstone, particularly Indian sandstone, develops the famous black spots within a few years — these are caused by a lichen that bonds chemically into the stone and won't shift with water alone. Limestone has a calcium-carbonate base that reacts with acid cleaners, so the wrong chemistry can cause permanent etching. Slate's natural cleavage planes can flake under high pressure. And every porous stone holds onto stains stubbornly because the surface is full of microscopic pores.

We approach every stone job with a test patch first. Pressure setting, detergent type and dwell time are all calibrated to the specific stone in front of us, not to a one-size-fits-all formula.

Black spot removal

If you have an Indian sandstone patio, you almost certainly know what black spot is — and you've probably tried scrubbing them off with no success. Black spots are a lichen called Verrucaria nigrescens that fixes itself into the stone with a chemical bond. Domestic washers can't shift them because the lichen is below the surface, not on it.

We tackle black spot in two stages: a specialist biocide that kills the lichen at the root, then a controlled pressure wash that lifts the dead growth. Done correctly, the spots come out and stay out for years. We're upfront about cases where very old, very deep spotting may leave faint shadows — but in the vast majority of jobs the result is dramatic.

Cleaning historic stonework

We work on heritage and listed stone where careful methods are required. We use poultice systems for delicate facades, doff steam systems for sensitive listed buildings, and gentle biocide-only cleans where any pressure could be a risk. We're happy to liaise with conservation officers, heritage architects and church wardens to agree the right approach for sensitive jobs.

If your project is listed and you're not sure what's permitted, give us a call and we'll talk through the options. We'd rather help you reach the right answer than win the wrong job.

Stone restoration after cleaning

After cleaning, natural stone often benefits from sealing — particularly porous stones like sandstone and limestone. A breathable penetrating sealer (we never use surface sealers on stone) deepens the colour, repels stains and slows the regrowth of algae and lichen. We use products from Lithofin, Aquamix and similar specialist suppliers.

We can also re-point stone walls and patios where the joints have failed, though for major restoration work we'd recommend a specialist stone mason.