Many of the stone buildings we see today were built hundreds of years ago and they’re still standing! Stone is an incredibly strong and durable material but the effects and strain of weather and, more recently, pollution are visible on many stone buildings. Though marks and stains on stone are inevitable, they can be safely removed. Unwanted matter on stone and brick is often unsightly, but did you know it can also be detrimental to the health of the stone too? For this reason, it’s important to remove anything that’s unwanted from the stone.

There are two main methods of stone cleaning: the DOFF method and the TORC method. This blog article explains how each works and when they’d be needed. Stone can’t be cleaned using either method by a layman. Both require a high level of training and expertise and specialist equipment, so you’ll need to call in a professional team. Underwood and Weston are qualified and approved by Stonehealth Ltd to use both methods outlined in this article. 

DOFF Method 

What is it? DOFF is a cleaning method ideal for removing paint, moss, algae, fungi, chewing gum and other biological matter from stone and brick. (Though it can also be used on terracotta, tiles, faience, concrete and even wood.) 

How does it work? In simple terms, it uses steam to clean the stonework. We will bring all the equipment needed for cleaning with us. The system uses a Hotbox to heat water to up to 150°c. This high temperature water is then sprayed onto the stone to clean it. The temperature of the water means that the matter is not only removed, but, in the case of moss, algae or fungi, it is killed off too. Whilst the water is very hot, the pressure is gentle and the volume of water is actually very low, meaning there’s no damage to the stone itself. The stone dries within minutes with no residue leftover. 

Is it bad for the environment? There are zero chemicals involved with the DOFF method – it’s just water, steam and heat. Cleaning stone this way causes no harm to the environment. Any debris that is removed from the stone is separated from the water and disposed of accordingly, while the water can simply run back into the ground. 

TORC Method 

What is it? TORC is a cleaning method ideal for removing carbon pollutants from stone. It can also remove oxidised bitumen, limescale efflorescence and paint or plaster residue. We can use the TORC method on stone, brick, ceramic tiles, terracotta, concrete, some metals and even on glass. It’s a well-regarded, gentle and effective method. TORC has been used on several prestigious buildings across the country including Hampton Court, Westminster Abbey and even Buckingham Palace. 

How does it work? The TORC system creates a swirling vortex using a mixture of low air pressure, a small amount of water and a safe inert fine granulate. This mixture is sprayed onto the stone using a specially designed hose and nozzle and the fine crystals safely remove any unwanted matter. The important thing to remember with TORC cleaning is that it’s not a heavy, high power blast, instead, it’s a very gentle technique. Again, we bring the cleaning system with us. 

Is it bad for the environment? No. We use only Stonehealth approved aggregate. This contains less than 1% quartz and no other from of crystalline silica. It is safe for the environment and non-toxic. 

Your building or monument might need just one method or, sometimes, they go hand in hand and both methods are needed to get the best results. Our stone cleaning services can be used on any construction made of stone, regardless of age or size. This includes monuments, churches, stately homes, listed buildings and smaller, residential properties too. 


Are you looking for a company to clean your stone building? Underwood and Weston are fully trained and qualified in both the DOFF and TORC methods and can advise on which technique will work best for you. Call us on 01604 753184 for more information.