Cotswold limestone, Bath stone, Regency stucco and old brick cleaned with superheated low-pressure steam. Temperature does the work, so the face of the stone stays where it is. Free survey and test panel before anything else happens.
Cotswold limestone is soft and porous. So is Bath stone, so is most of the sandstone in the Forest, and so is lime-mortared brick. All of them have a weathered outer skin — a slightly harder, denser face that has formed over decades and is doing a real job protecting what's behind it. Take that skin off and the stone underneath weathers far faster than it did before.
High-pressure water takes it off. So do grit and sand abrasives, and so does acid, which additionally attacks the lime mortar in the joints and can leave staining that surfaces months later. The classic result is a building that looks bright for one season and then greens up faster and holds more dirt than it ever did — because the surface is now open.
The method the conservation world has settled on is heat. Superheated water applied at very low pressure and low volume: the temperature breaks down biological growth and softens soiling so it can be rinsed away, without abrading anything. We run a custom-built superheated water system that works on the same principles as a DOFF — low pressure, low water volume, heat rather than abrasion doing the work.
We're not a Stonehealth-accredited contractor and we won't pretend to be. We're also not going to tell you our machine is identical to somebody else's. What we will do is give you the operating temperature, pressure and water volume in writing, clean a test panel on your own building, and let the panel make the argument before you commit to anything.
The county's signature stone and the softest thing we work on. Steam only, low pressure, no abrasives. Lifts algae, lichen and general soiling. Hard black sulphation crust — the stuff that builds on sheltered elevations rain never washes — is a separate conversation: sometimes heat and patience shift it, sometimes it's better left alone.
Ashlar faces, quoins, mullions and dressed detail. Fine detail is where pressure washing does its worst damage, so it's where the method matters most.
Cheltenham's painted and rendered frontages. Effective on the biological growth that shades render green and grey, at a temperature and pressure set to leave sound paint alone — which is exactly what the test panel is for, because old coatings vary enormously and some are already letting go.
Soft Victorian and Georgian brick where the mortar is softer than the brick. No acid — it eats lime mortar and re-deposits salts that bloom back out weeks later.
Memorials, chest tombs and church masonry. This work runs slowly and carefully, and we document it where the faculty process requires it.
Stone slate roofs, oak framing, weatherboarding and lead. All handled at the temperature and pressure the material will take, which is usually less than people expect. Timber especially — heat and water raise the grain and will take limewash off, so that is always a test-panel decision.
We identify the substrate, the type of soiling and the condition of the mortar and any previous repairs. Loose pointing and open joints get flagged before any water goes near them.
We don't skip this one. We clean a small, agreed area, let it dry fully, and you look at it in daylight. That panel sets the standard for the whole job and settles how clean is clean.
Superheated steam at low pressure, worked methodically across the elevation. Repeat gentle passes on stubborn areas — never a step up in pressure. Ledges, cills and detail done by hand.
Once it's dry we walk it with you. If the survey turned up pointing or drainage issues that will bring the growth straight back, you'll get that in writing — cleaning a wall that a broken downpipe keeps soaking is money wasted.
Priced per elevation after a survey, never off a rate card. The variables that actually move the number are access (scaffold or a powered platform is often the single biggest line), the type and depth of soiling, and how much hand-detailing the stonework needs.
A single domestic elevation in Cotswold stone is a day or two. A church, a large listed frontage or anything needing scaffold is quoted properly with the access costed separately so you can see what's cleaning and what's getting us to it.
The test panel is free and comes before the quote is finalised. If you look at the panel and decide the building is better left as it is, that's a perfectly good outcome and you owe us nothing.
Done properly, no — that's the whole reason for using it. The pressure is a fraction of a pressure washer's and there's no abrasive, so the weathered face of the stone stays intact. The risk with old stone is almost always too much pressure or the wrong chemistry, and the test panel exists to prove neither is happening on your building before we go any further.
Often, yes — and it's worth settling before anyone starts. Cleaning a listed building can count as alteration affecting its character, which needs listed building consent, and carrying out those works without it is a criminal offence for the contractor as well as the owner. It's judged case by case: gentle removal of biological growth by a demonstrably non-damaging method is frequently treated as maintenance, while anything that changes the appearance of the fabric is far more likely to need consent. We won't start on a listed building until there's a written answer from your conservation officer, and we'll supply a method statement and test-panel photographs for them to look at. An unlisted building in a conservation area doesn't need consent to be cleaned.
It works on the same principles — superheated water at low pressure and low volume, with heat rather than abrasion doing the work — using our own custom-built system rather than a Stonehealth-branded one. We're not a Stonehealth-accredited contractor and we won't pretend otherwise. We're happy to give you the operating temperature, pressure and water volume in writing for your conservation officer, and to clean a test panel so you can judge the result on your own building rather than on a brand name.
Heat kills far more of the growth than cold water does, rather than just washing the green off the surface, so it tends to come back more slowly. It doesn't sterilise the stone — nothing does. Where regrowth is likely we'll discuss a gentle biocide as a separate decision: on some historic fabric that's the right call and on some it isn't.
Yes — memorials, chest tombs and church masonry. That work runs slowly and carefully. Church of England buildings in use for worship are exempt from listed building consent but go through the faculty system instead, and we'll work to whatever the diocese asks for, including List B permission from the archdeacon for minor works. Worth knowing that an individual memorial or chest tomb can be listed in its own right, separately from the church.
Send us a postcode and we'll arrange a survey and a free test panel — or WhatsApp a photo straight to 07555 141504. Listed buildings, churches and conservation areas welcome.
