Brick and Stone Cleaning Methods and What to Avoid

Cleaning brickwork or stone can help remove heavy soiling, but the wrong method damages masonry for good. Washing exterior walls typically costs between £200 and £400 per wall, depending on the level of dirt and how easy the wall is to reach. A partial clean may be all that is needed, and leaving well alone is a valid option. Council conservation guidance warns that cleaning should only be part of a wider programme of surface repairs.

Should you clean your brick or stone at all?

Decisions on whether and how to clean depend heavily on the materials involved and the type and amount of soiling. Heavy soiling on some stones can retain water and hold harmful agents against the masonry.

Lighter soiling may not be very harmful to the building fabric. A partial clean may be all that is needed to restore the appearance of an exterior wall. You will not get a totally clean finish.

According to council conservation guidance on cleaning historic buildings, leaving well alone is a valid option on both brick and stone. You should take expert advice on the need for cleaning and the best method for your specific property. Cleaning should not be an isolated cosmetic task, but rather part of a wider programme of surface repairs.

Why older brick and soft stone need extra care

You must identify the materials accurately before agreeing to any work. Old brickwork is softer than new brick and reacts badly to aggressive washing. Special rubbed bricks need special consideration because even a soft bristle brush can cause damage to their delicate surface.

You should get expert advice to identify stone, as its resistance to cleaning varies significantly. The softer the stone, the greater the risk of damage from water or friction. Iron content in the stone can also cause staining.

Dirt on limestone and marble is generally soluble in water. Over-saturation can cause staining and wash out the joints. No washing should take place in winter months because freezing water inside the brick or stone can cause further damage as it expands.

Cleaning methods from gentle to aggressive

Contractors use several methods to clean exterior walls, and you should always start with the gentlest option. The main methods for masonry cleaning are:

• Washing, which uses water to soften dirt and a soft brush to remove it.
• Pulsed water sprays, which are effective on stubborn dirt.
• Chemical cleaning with acid, which is effective but dangerous and requires a suitably experienced contractor.
• Mechanical cleaning, which is a last resort and not suitable for soft or flaky surfaces.

The main problem with washing is staining. A careful contractor will use a minimum amount of water and will not let it run down the building. Do not abrade the surface of brick with hard brushes. On special rubbed bricks, even a soft bristle brush can cause damage.

Mechanical cleaning should be avoided on brick unless there is no alternative. Scouring the surface encourages re-soiling and accelerates decay. If you have a rendered property rather than exposed brick, the approach changes completely. You can read more about cleaning your rendered walls.

What exterior wall cleaning costs

Washing exterior walls is priced according to the size of the job, the level of dirt and how easy the wall is to reach. Larger jobs such as a full property exterior can push costs up to around £1,800. High walls may need scaffolding, which increases the final bill.

The table below shows typical prices and timeframes for washing standard exterior walls.

These are typical published prices for 2026, and local quotes will differ. Washing exterior walls costs around £200 to £400 per wall, or about £6 to £12 per square metre. Prices are usually higher in London and the South East. These figures apply to standard exterior wall washing, and historic or specialist cleaning is quoted individually based on the condition of the masonry.

Listed buildings and when you need consent

Simple cleaning of a listed building using water would not normally require listed building consent. Other methods or more extensive restoration work might well need consent before a contractor can start work.

If you are in any doubt about the status of your property or the method proposed, contact your local council conservation officer before work begins.

Protecting windows, doors and decorative features

You must protect areas not being cleaned to prevent damage. A good contractor will:

• Cover doors and decorative features to stop dust and debris getting inside.
• Rinse all window glass thoroughly to remove alkaline solutions or acids.
• Keep harsh alkali solutions away from specialist self-cleaning glass coatings.
• Avoid using solutions containing hydrofluoric acid or fluorine compounds on coated glass.

Glass makers warn that glass is durable, but alkaline solutions and some acids can damage it. Leaching and efflorescence from concrete, bricks and mortar can be particularly harmful if washed onto the windows.

Deposits should not be left on glass, where they can slowly attack it or cause staining and etching. This is why the windows, doors and decorative features should be protected and rinsed. If a cleaner leaves streaks on your glass after the masonry is washed, you can read our advice on cleaning glass without streaks to understand what went wrong. You can also learn more about protecting specialist coated glass.

Run off and your drains

Washing down exterior walls creates dirty run-off. Any substance not found naturally in an environment could cause pollution, for example detergents used to loosen dirt.

Surface water drains discharge directly to the environment. Government guidance for England says a business must make sure contaminated water from its activities goes into the foul drain with the water company's permission. Alternatively, the water must be recycled or removed by a registered waste carrier.

Pollution can bring an unlimited fine. You should ask your contractor exactly how they plan to capture and dispose of the run off before you agree to the work.

Testing a small patch first

You should always test an inconspicuous patch first. This allows you to see what problems may result from the chosen cleaning method before it is applied to the whole house.

A test patch shows how the brick or stone reacts to the water pressure, the brush or the chemical. Wait for the test area to dry completely before you judge the result, as wet masonry looks very different to dry masonry.

Choosing a contractor for masonry cleaning

Always use a reputable and experienced contractor. Ask for examples of previous work if the technique involves more than water. A good commercial contractor will provide a written risk assessment and a method statement detailing exactly how they will carry out the work safely.

Check that the business holds public liability insurance and ask for a current certificate. This is not a legal requirement for most UK businesses, but it is the cover that pays compensation claims for accidental injury to members of the public and damage to their property. Employers' liability insurance is compulsory for a business with employees.

The Federation of Window Cleaners is a non-profit trade body with a code of practice, a safety accreditation scheme and training. Membership is voluntary, so treat it as one good sign among several when choosing a firm that offers exterior cleaning.

Under the Consumer Rights Act 2015, a service must be carried out with reasonable care and skill. If it is not, you can ask for it to be put right or for money back. A quote is a fixed price, whereas an estimate is not. A service agreed on the doorstep, by phone or online normally carries a 14-day cooling-off period.

The Health and Safety Executive says ladders can be a sensible option for low risk, short duration work, including domestic window cleaning on lower floors. However, the Work at Height Regulations 2005 require work at height to be properly planned, done by competent people and avoided where reasonably practicable. This is why many cleaners now work from the ground with poles.

Do not attempt to clean upper storeys yourself. Working at height remains one of the biggest causes of fatalities and major injuries. Common cases include falls from ladders and through fragile surfaces. The law asks for competence, not a formal qualification, but taller buildings may need powered access platforms or rope access. Leave high walls to professionals.

In Scotland, most councils require window cleaners to hold a window cleaner licence under the Civic Government (Scotland) Act 1982, and licence holders carry identification. Requirements vary by council.

Industry guidance produced with the Health and Safety Executive says water-fed poles must not be used near overhead power lines. You should point out any overhead cable to the cleaner before they begin.

Common questions

How to clean sandstone

You should get expert advice to identify the stone accurately, as its resistance to cleaning varies. The softer the stone, the greater the risk of damage, and over-saturation can cause staining and wash out the joints. Mechanical cleaning is a last resort and is not suitable for soft, flaky surfaces.

What facade cleaning involves

Facade cleaning usually starts with water to soften dirt and a soft brush to remove it. Pulsed water sprays are effective on stubborn dirt. Chemical cleaning with acid is effective but dangerous, so it should only be handled by a suitably experienced contractor.

How to clean bricks safely

You should use a minimum amount of water and not let it run down the building, as the main problem with washing is staining. Do not abrade the surface with hard brushes, and avoid mechanical cleaning unless there is no alternative. Scouring the surface encourages re-soiling and accelerates decay.

Do I need stone cleaning services for green walls?

Heavy grime or algae takes five to six hours to clean on a single wall and typically costs between £250 and £400. Leaving well alone or a partial clean is a valid option because you will not get a totally clean finish. If you hire a professional, ensure they test an inconspicuous area first.

Next steps

Before you book a contractor to clean your exterior walls, work through this checklist:

• Take expert advice to identify your stone or brick type accurately.
• Consider a partial clean or leaving well alone if the soiling is light.
• Check with your local council conservation officer if your building is listed.
• Ask for examples of previous work if the contractor uses anything more than water.
• Agree a fixed quote rather than an estimate.
• Check the contractor has a written method for protecting windows, doors and decorative features.
• Ask for a current public liability insurance certificate.
• Confirm that contaminated run off will go to a foul drain or be removed by a registered waste carrier.

Taking the time to check the method and the contractor helps prevent lasting damage to your masonry. When you are ready to get quotes, you can find a window cleaner near you who also offers exterior wall cleaning.