Why is your brick colour turning into green? And what can you do to prevent it?

Brick Colour Turning into Green: A Scientific Explanation

Bricks are a popular choice for both indoor and outdoor use and a favourite or we can say it’s a To-go choice for both residential and commercial buildings. They are strong, due to their durability and aesthetic appeal. However, One challenge with brick walls is that the bricks can develop a greenish tint over time due to algae growth. The porous, rough surface of bricks can allow algae and moss to take hold, especially in damp, shady areas.

This is usually due to the presence of copper in the bricks, which reacts with the atmosphere to form a green patina. While a few green spots of algae on a brick wall may not bother some people, others may find the discolouration unsightly and want to remove it to keep their wall looking clean and fresh. The good news is that there are several effective ways to remove the green patina from brick walls.

This article will explore why brick walls can turn green over time and provide some useful tips for preventing algae growth. Then we will help you select a strategy to clean it yourself or make arrangements for professional cleaning services.

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The science behind why bricks turn green

The green tint that can form on brick walls happens due to a chemical reaction between the iron in the clay bricks and oxygen in the air. The interaction between the iron in bricks and oxygen in the air is called oxidation. This process causes the iron to rust, and on bricks, this rust appears as greenish-black stains on the surface. These ugly discolouration’s are the result of the oxidation process.

As the oxidation process continues, the iron is slowly consumed and eventually pyrites or pyrite nodules (a sulfide mineral) form in its place. As time passes, these nodules cause the affected bricks to spall – a condition that refers to pieces of the brick being forced off as a result of breaking down. This further damages the brick wall, as well as any exposed structure/brickwork around it, eventually causing structural instability. This condition can be reversed through professional cleaning services. Pressure washing is generally used for light-to-medium discolouration cases, while chemical cleaning is typically required for more severe instances where rust has taken hold.

Protecting your bricks from turning green

Many people think that using bleach will solve the problem. In reality, bleach isn’t a good solution because it will only remove the green layer without affecting the rest of the brick. Instead, it is recommended to use something else to remove the stain.

If you have ever had to clean bricks from turning green, you know how difficult it can be.

  • First, you will need to gather some supplies. You will need a bucket, some soap, and a brush. You may also need a pressure washer, depending on how bad the green is.
  • Once you have your supplies, you will need to wet the bricks with the soap and water. Make sure to scrub them thoroughly. You may need to use the pressure washer to remove all of the green area or that green coloured area.
  • Once the bricks are clean, you will need to rinse them off. You can do this with a hose or a bucket of clean water. Make sure to let them dry completely before using them again.

Following these simple and easy tips, you can keep your bricks looking their best for years to come.


Brick colour turning green is a scientific phenomenon caused by a chemical reaction between the bricks and the environment. The most common cause of this is iron oxide in the bricks reacting with C1 in the air. This reaction is accelerated by moisture, so bricks in damp or humid environments are more likely to turn green. If you have green bricks on your property, it is recommended that you arrange for professional cleaning services.