Cleaning stone without damaging it

Cleaning stonework is one of those jobs where the wrong approach does permanent harm. Cotswold stone is a soft, porous limestone; blast it with high-pressure water or grit, or wash it with acid, and you strip away the weathered surface — the "case-hardened" face that has been protecting the stone for decades. The building looks raw for a season and then decays faster than it ever did before.

So our starting point is always the gentlest method that will do the job, and a test patch in a discreet corner before anything else. Sometimes the honest advice is that stonework doesn't need cleaning at all — a naturally weathered wall is part of a building's character — and we'll tell you that too.

What we clean

  • House frontages and elevations — lifting general atmospheric dirt and grime from Cotswold stone and other masonry.
  • Algae, moss and biological growth — the green and black organic growth common on shaded, damp elevations and garden walls.
  • Garden walls, steps and paving — stone boundary walls, terraces, steps and flags made slippery or unsightly by organic growth.
  • Staining — rust runs, copper staining, and staining from fixings and rainwater goods, treated with poultices and appropriate chemical cleaners.
  • Paint and coating removal — carefully removing old masonry paint and failed sealers from stone, where the stone beneath is sound enough to take it.
  • Post-repair cleaning — blending cleaned and repaired areas so an elevation reads as one surface again.
Before and after: a Cotswold watercourse and its stone banking, cleared of algae and silt
Before and after on a Cotswold watercourse — algae and silt lifted from the stone banking without damaging the weathered faces.

How we choose the method

There is no single "stone cleaning" technique — there is a ladder of methods, and the skill is knowing where to stop:

  1. Dry brushing and hand cleaning — for loose dirt and growth; the least aggressive option and often enough for garden walls.
  2. Low-pressure water washing — controlled washing that softens and lifts dirt without driving water into the wall or eroding the surface.
  3. Steam / superheated water cleaning — highly effective on biological growth and greasy urban grime, using very little pressure and very little water; usually our preferred method on soft limestone.
  4. Biocide treatments — killing algae and lichen at the root so regrowth is slowed, used selectively and appropriately.
  5. Poultices and specialist chemical cleaners — for specific stains, always tested first and always neutralised properly.

What we don't do is aggressive high-pressure blasting or acid washing of soft limestone. If someone quotes you a suspiciously cheap price to "jet wash" a Cotswold stone house, that's what you're being quoted for — and the stone will pay for it later.

When cleaning is worth doing

Cleaning makes the biggest difference when:

  • a sale or refurbishment makes first impressions matter;
  • biological growth is holding moisture against the stone (damp, shaded elevations);
  • steps, paths and copings have become slippery and unsafe;
  • staining or old paint is disfiguring an otherwise sound elevation;
  • restoration work has left a patchwork that needs blending.

Cleaning also reveals the true condition of the stonework — it often pairs naturally with repointing and restoration, and we can quote for both together so the wall is only scaffolded and worked on once.

Where we work

We clean stonework across Gloucestershire and the Cotswolds, including Cheltenham, Winchcombe, Gloucester, Tewkesbury, Broadway, Stow-on-the-Wold and Cirencester.

Frequently asked questions

Can you clean old stone without damaging it? Yes — provided the method is matched to the stone and the soiling, and tested first. That is exactly why we start with a test patch and the gentlest effective technique, and why we avoid high pressure and acids on soft limestone altogether.

Will the algae come back? On a damp, shaded wall, eventually — that's its environment. A biocide treatment slows regrowth considerably, and dealing with the moisture source (overhanging vegetation, leaking gutters, poor drainage) slows it further. We'll point out anything like that while we're on site.

Can you remove paint from stone? Usually, yes, using appropriate paint removal systems rather than blasting. The condition of the stone underneath matters, so we assess and test before quoting.

How much does stone cleaning cost? It depends on area, access, soiling and method, so we quote per job after seeing the stonework — a free written quotation, with a test patch where useful so you can see the result before committing.