How to clean bricks

Everything you need to know about cleaning brickwork, including removing efflorescence and mortar.

One of the key benefits of using clay facing bricks is that brickwork usually requires little maintenance over the course of its life. However, there may be times when you need to clean brickwork – this guide covers how to clean clay brickwork and remove the most common types of stains you may see on both old and new brickwork.

The information provided here is intended as guidance, but we highly recommend consulting a brick cleaning expert, especially for stains that are extensive or hard to identify, as the method of cleaning depends on the nature of the stain.

Preventing staining and damage
Dirt and grime
Efflorescence
Lime staining
Metallic staining
Peacocking or picture framing
Cement and mortar staining
Paint
Moss and vegetation

Preventing staining and damage on brickwork

As the saying goes, prevention is better than a cure, and that’s true for keeping brickwork clean and damage-free.

On site, bricks should be stored in a safe area, kept dry and protected from the elements and the dirt created by ongoing surrounding work.

When laying bricks, a high quality of work will go a long way to keep bricks clean and free from mortar smears and stains. A good bricklayer will be able to keep joints tidy and avoid dropping mortar on brick faces. Mortar joints should be fully filled so that no pockets are left for water to collect and ultimately penetrate the clay brick. Furthermore, correctly installing the Damp Proof Course (DPC) and Damp Proof Membrane (DPM) will protect the brickwork from long-term water saturation and the resulting staining and damage.

Once brickwork is completed on site, it should be covered and protected from other ongoing work, which can create dirt that stains the finished brick wall.

Dirt and grime on brickwork

Airborne soot and dirt will naturally build up on brickwork over time, depending on the location of the building. This is natural and will not damage the brickwork, but may impact the look of the building.

How to clean dirty brickwork

Use a detergent solution and apply to the brickwork using a nylon brush. Never use a wire brush or metal tools to clean, as this can damage the brick face. Avoid cleaning brickwork in very cold conditions, as the wet brickwork will freeze, which many cause damage.

High pressure washing is not recommended for brickwork. Despite bricks being highly durable when designed and constructed correctly, brick surfaces and mortar joints can be damaged under high pressure, leaving the brickwork vulnerable to water penetration and frost attack.

If you wish to clean a historical building with older brickwork, a survey should be carried out by a specialist brickwork cleaning contractor to avoid damage.

Download our guide to water pressure washing brickwork

Efflorescence on brickwork

What is efflorescence?

Efflorescence is one of the most common types of brick stain, presenting as a white powdery 'bloom' or mark. These white stains on brickwork are the result of the formation of soluble salts on the surface of clay bricks, following saturation.

All clay bricks contain soluble salts, but when water comes into contact with the brick, it dissolves the salt. As the brick then dries again, this dissolved salt is drawn to the surface and appears as a white, crystalline powder. The amount of efflorescence that appears on the surface depends on many factors, including the type of salt, crystal shape, the bricks’ pore structure, and the ambient temperature in the environment.

How to prevent efflorescence

Efflorescence will only happen when bricks become wet, whether in storage or during the construction process. This is why it is essential to protect materials in storage and protect partially built walls during construction.

How to clean efflorescence off brickwork

Efflorescence is generally a harmless and temporary effect that should weather away with time.

You can aid this process by gently spraying the walls to simulate rain, but high-pressure hoses should not be used, as this will further saturate the brickwork, resulting in more salts coming to the surface of the brick. If the brickwork is a natural internal finish, you can apply a damp sponge, rinsing frequently in clean water, to minimise the appearance of the stain.

Download our guide to efflorescence

White efflorescence stain on brickwork — Efflorescence appears as a white powdery mark, caused by bricks becoming wet during storage or construction

Lime staining on brickwork

What is lime staining?

Lime staining, or lime leaching, happens when excess water flows through cement or mortar. The water dissolves calcium hydroxide (free lime) which is then deposited onto the brick face. The calcium hydroxide then reacts with carbon dioxide in the air, producing a hard crystalline formation of calcium carbonate.

Although lime staining is a white stain like efflorescence, its cause and treatment is very different. Lime leaching characteristically forms in a dribbling pattern from holes or fine cracks between brick and mortar joints. Lime staining commonly comes from mortar joints, or concrete and cast stone elements, such as floor slabs built into brickwork.

How to clean lime staining off brickwork

The initial staining that occurs with lime leaching can be removed using water and a brush. However, once the calcium hydroxide has reacted with the air and formed calcium carbonate, this can only be removed by an acid solution.

Propriety brickwork cleaners tend to be hydrochloric acid based, therefore it is essential to follow all instructions and take appropriate precautions. It is important to pre-wet brickwork before applying the chemical cleaning solution, and only small areas should be treated at a time. It is also advisable to test a small test area before applying widely.

Download our guide to lime leaching

Metallic staining on brickwork

What is metallic staining?

Metallic staining on brickwork can be caused by iron, manganese or vanadium.

Iron is a normal, natural part of clay’s composition, while manganese may be added as part of the production process. Iron staining happens when compounds of iron are drawn to the surface of the brick as a result of moisture. On the surface, the iron oxidises when in contact with the air and produces a rust-like stain.

Manganese staining is caused by manganese dioxide, used as a colouring agent during manufacturing, that has dissolved in rainwater, construction water, or muriatic acid. It appears as a dark brown or black stain.

Vanadium is a mineral element found in raw clay and is most commonly found in the production of buff-coloured bricks. As a soluble salt, vanadium can be brought to the surface by moisture and appears as a stain that can be yellow or green.

Iron staining on new brickwork — Iron staining is caused when iron oxidises on the brick's surface

Green vanadium stains on buff brickwork — Vanadium stains are most commonly found on buff bricks

How to clean metallic stains off brickwork

Iron and manganese stains are best left to weather away naturally. If you need to accelerate this process, you can remove the stain from the face of mortar joints with a rough file. You can also apply a proprietary brickwork cleaning solution.

Vanadium staining should be treated differently. You should not use a hydrochlroric acid-based cleaning solutions, as this can cause a reaction that makes a permanent dark-coloured stain. If necessary, vanadium stains can be treated with a dilute oxalic solution, but always try a small test in a discreet area to gauge the success of the treatment first.

Download our guide to metallic staining

Peacocking and picture framing on brickwork

What is peacocking and picture framing?

Peacocking most commonly appears on blue bricks as an oily-coloured stain on the face of the brick. When the oily stain appears around the edge of the brick, this is known as picture framing. Peacocking and picture framing is caused by brickwork saturation prior to mortar curing, or through the use of excessively wet mortar.

Picture framing appears around the edge bricks

Peacocking on blue bricks — Peacocking appears as an oily stain, commonly on blue bricks

How to clean peacocking and picture framing stains

Peacocking and picture framing is not harmful to the durability of bricks. The effect will tone down with weathering, but will not weather away completely. Therefore, prevention is better than cure. Stored bricks and newly laid brickwork should be kept dry and clean. Freshly laid brickwork is particularly vulnerable in the first three to five days as the mortar cures. Use waterproof sheeting to protect fresh mortar and open cavities to prevent saturation.

Download our guide to peacocking

Cement and mortar staining on brickwork

What is cement staining?

Cement stains on brickwork can occur during construction, due to splashes or smearing, or afterwards, when run-off from concrete components leaves a residue on the finished brickwork.

The most common cause is splashes during the bricklaying process, or if mortar joints are brushed before the mortar is fully set. A skilled bricklayer will be able to avoid this as much as possible to prevent excessive cement staining.

How to clean cement stains off brickwork

When mortar is splashed or dropped onto brickwork during construction, it is usually best to wait for it to harden slightly before removing – avoiding smearing the mortar into the face of brick. For larger deposits, remove with wooden tools, rather than metal, to avoid damaging the brickwork.

For mortar and cement smears, removal may be more difficult. You can buy specialist cement cleaning products, but test on a small area first and always follow the instructions on the label. If in doubt, consulting a brick cleaning contractor is advisable.

Paint on brickwork

Paint can be very difficult to remove, particularly aerosol paints that are commonly used for graffiti. Facing bricks with a very textured surface, such as handmade bricks, will allow the paint to penetrate further into the surface, making it harder to clean.

How to clean paint off brickwork

Because paint is difficult to clean off brickwork, consulting a specialist brick cleaning contractor is always advisable.

The method of cleaning depends on the composition of the paint. For example, acrylic-based paints will require a different type of paint remover compared to polyurethane or epoxy paints.

If the paint is still fresh, soak up as much as possible, being careful not to wipe and further spread the paint. You can then use a solvent on the area before washing with warm water and detergent. Remember to follow any safety instructions on the paint remover or solvent.

If the paint is dry, you can carefully scrape off as much as possible before applying a paint remover, following the instructions. If there are numerous layers of paint, you may need to use different types of paint remove for each layer, depending on the paint type. It is always advisable to test the remover in a small area first, before applying to the rest of the brickwork.

Brick tinting may be required after paint removal to restore the brick to its original colour. Again, consult a brick cleaning specialist for advice on tinting.

Moss, algae and organic growth on brickwork

Moss and algae may naturally grow on brickwork, as well as larger creeping plants such as ivy. Be aware that green stains may not be moss or algae if they appear on buff-coloured bricks – this could be vanadium, a type of metallic stain.

Organic growths can trap water around the surface of the brick and mortar, leading to potential frost damage from repeated freezing and thawing.

How to remove organic growth from brickwork

Moss, algae and lichens thrive in damp, cold, shaded areas. If these conditions can be addressed, the organic matter will usually reduce without a chemical treatment. If this is not possible, you can remove any loose growth then apply a surface biocide to prevent and destroy growth. It is most effective to apply biocide during drier weather to prevent dilution. Test a small inconspicuous area first and follow all manufacturers’ instructions.

Download our guide to organic growth removal