How to Clean Stone Walls
Over time, stone walls naturally collect dirt, algae, and moss — especially in Cornwall’s damp coastal climate. While some people love that weathered look, too much build-up can trap moisture and cause damage over time. Cleaning your stone walls properly can bring back their original colour and texture without harming the stone itself. Here’s how to do it safely and effectively.
What Is the Best Thing to Clean Stone Walls With?
The best cleaning method depends on the type of stone and how dirty it is.
For most outdoor stone walls, the safest and most effective cleaner is warm water, a mild detergent, and a soft-bristled brush. This removes surface dirt and algae without damaging the stone’s surface.
If the wall has heavy algae or lichen, a biocide or stone-safe cleaner (such as a diluted D/2 or Wet & Forget solution) can help — just make sure it’s pH neutral and safe for natural stone.
Always test on a small area first, as some stones (especially limestone and sandstone) can react badly to harsh chemicals.
How to Refresh a Stone Wall
Refreshing a wall isn’t just about cleaning — it’s about reviving its natural colour and structure.
Here’s a simple approach:
1. Remove loose debris with a stiff brush or broom.
2. Clean gently using warm water and mild detergent — avoid acid-based cleaners.
3. Rinse thoroughly with clean water to remove any residue.
4. Check for damage — cracks or loose stones may need repair before cleaning more deeply.
5. Repoint if necessary using lime mortar to stabilise and refresh the appearance.
For older walls, light cleaning followed by repointing can make a dramatic difference — giving it that “refreshed” look without scrubbing away character.
Can I Pressure Wash a Stone Wall?
You can, but only with caution. High-pressure washers can easily strip mortar, damage soft stone, and force water deep into joints where it can cause frost damage later.
If you do use a pressure washer:
Keep it on a low-pressure setting.
Stand at least a metre back.
Avoid focusing on one area for too long.
For most stone walls — especially old or lime-mortared ones — gentle hand cleaning is the safest approach. When in doubt, get professional advice before using any jet washer on historic or natural stone.
What Should You Not Use on Natural Stone?
Avoid the following at all costs:
Acid-based cleaners (e.g. brick acid) – these can burn and permanently discolour stone.
Bleach or harsh household chemicals – they strip away the stone’s natural finish.
Wire brushes or grinders – they scratch and weaken the surface.
Salt-based products – they draw moisture into the stone, leading to cracking and efflorescence.
Natural stone is porous and needs gentle care — think restoration, not scrubbing.
Stone Walling in Cornwall
At Woodland Stonework, we don’t just build stone walls — we help keep them looking their best for years to come. Whether you need cleaning, repairs, or full restoration, we use traditional methods and local materials to bring out the natural beauty of Cornish stone.
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For advice or a quote on stone wall cleaning in Cornwall, get in touch today — we’ll be happy to help.