Sandstone. Ruined.

We've discussed sandstone before. Lets discuss it again. You will see images like the ones in today's blog all over city centres. The Graffiti ink might be gone, but what is left is far more permanent and much more expensive to fix.

Sandstone is a beautiful, character-rich building material found across the UK, particularly in the two cities of Glasgow (predominantly red sandstone) and Edinburgh (predominantly blonde Sandstone). But despite its sturdy appearance, sandstone is highly porous and relatively soft, meaning improper cleaning methods can do more harm than good.

A common mistake seen time and again is the use of standard pressure washing to clean sandstone façades, walls, and paving. While pressure washers can blast away dirt quickly, they also strip away the stone’s natural surface, erode mortar joints, and push water deep into the stone — setting the stage for long-term damage.

Evidence of poor graffiti removal which has carved and pitted the stone.

The Problem with Pressure Washing Sandstone

Pressure washers are built for force, not finesse. Here’s what can go wrong:

• Surface erosion: High-pressure jets wear down the stone’s face, exposing softer layers beneath and accelerating degradation.

• Increased porosity: By opening up the surface, pressure washing actually makes sandstone more vulnerable to permanent graffiti in the future. This owing to increased surface area and a primed surface.

• Moisture retention: Water driven into the stone can become trapped, leading to salt efflorescence, freeze-thaw damage, and internal decay — all of which may not show up until years later.

• Mortar and joint damage: The pointing between stones is often softer than the stone itself, and high pressure can break it away completely, leading to instability.

In short, pressure washing may seem effective at first glance, but it often causes irreversible harm to your building’s fabric, especially on older or listed properties.

Ironically, the graffiti image is more permanent than it was before this poor attempt at removal!

This damage is completely irreversible and will require complete replacement of the stone.

A Better Way: DOFF style Steam Cleaning

If you’re looking to clean sandstone safely, DOFF & Thermatech cleaning are the gold standard.

The DOFF & Thermatech system uses superheated steam delivered at low pressure. It gently lifts dirt, algae, paint, and biological growth from the stone’s surface without saturating or damaging it. It’s especially well-suited for historic and porous materials because:

• Heat allows the stone to dry within minutes, preventing water penetration.

• It’s non-abrasive, meaning delicate carvings and features remain intact.

• It’s approved by heritage and conservation bodies across the UK and is a recommended choice by Historic Scotland.

Why DOFF style steam cleaning Is the Smart Choice

Steam cleaning isn’t just a cleaning tool — it’s a preservation system. Whether you’re maintaining a listed building in Edinburgh or restoring sandstone features on a city centre shopfront, DOFF gives you results without risk.

It’s ideal for:

• Heritage buildings

• City Centres

• Sandstone cladding and pillars

• Sensitive stone cleaning on listed façades

Looking After Our Buildings Properly

Cleaning sandstone is about more than making it look good. It’s about respecting the material and protecting our shared architectural heritage.

If you're considering cleaning sandstone surfaces, steer clear of pressure washing — and instead, choose a method that’s effective, gentle, and approved by conservation professionals.

For professional DOFF and Thermatech cleaning services across Scotland, get in touch today. We’ll help restore your building the right way — safely and sensitively.