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Why does mould grow in bathrooms?

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Why does mould grow in bathrooms?

By Ruth MacEachern

Product Manager

Dec 06, 2022

The most common place to see mould in a home is in the bathroom. Black patches can form quickly on walls, ceilings and around windows, and spread across different surfaces to create unsightly patterns that are difficult to clean and hard to prevent. If you have discovered mould in your bathroom or elsewhere in your home, understanding the causes will help you take the right steps to clean it away and stop it coming back.

Are you worried about toxic black mould?

Thera are thousands of distinct species of mould that can grow in your home, and some of them are very bad news. Toxic Black Mould, or Stachybotrys Chartarum, is a particularly dangerous species. It grows in large black patches on walls and ceilings, and releases chemicals called Mycotoxins that are harmful to health.

If you are worried that toxic black mould has started to grow in your home, it is essential that you have it professionally removed as quickly as possible to avoid risk to your health.

Other mould species are less harmful but can still make life miserable. Many people are allergic to the spores that mould uses to spread and encountering these spores can result in painful reactions on the skin, eyes, and if inhaled, can provoke asthma attacks.

Mould on bathroom walls

The most common cause of mould in bathrooms is condensation. If humidity levels are not properly controlled with good ventilation, water vapour can build up in the air, and when it reaches a cold surface such as an exterior wall or window, the vapour condenses into droplets of water. This condensation can soak through paint and cause damp patches to develop. These damp patches are the perfect environment for mould to grow.

Bathrooms should have a good extractor fan fitted that helps remove the humid air after you take a shower or bath, but many homes do not have sufficient ventilation in bathrooms, and as a result, will suffer from condensation.

According to building regulations, a bathroom requires an extractor fan that is capable of moving a minimum of fifteen litres of air per second to prevent moisture building up in the air.  If you are suffering from mould on your bathroom walls, it is likely that you have insufficient ventilation, and you may need to replace an existing extractor fan with a more powerful model.

Can you clean mould?

Toxic black mould needs to be cleaned professionally, but other moulds can be safely cleaned – although if you suffer from allergies, you may want to avoid coming into contact with it. A fungicidal spray or a mixture of dilute bleach should be sprayed onto the surface to kill the mould and then it can be wiped away with a soft cloth.

You should wear eye protection, gloves and a mask when removing mould, and dispose of any cleaning materials after you have finished to prevent spreading the mould to other rooms.

Unfortunately, simple cleaning is only a temporary solution. Unless you deal with the root cause of the mould it will grow back again. Even anti mould paints will only prevent mould growth for a short time. To prevent mould in bathrooms permanently, you need to reduce humidity levels.

Improving the ventilation in your home - either by updating the bathroom extractor fans, or installing a whole house positive input ventilation system such as Atmos will permanently stop the condensation that leads to damp and mould.

Learn more about Stopping Condensation >
Read our tips about preventing mould >


Get help

If you are concerned about mould in your bathroom, our local ventilation specialists can help. Simply enter your postcode below to find a local specialist who can visit your property to conduct a free home survey. In the survey, the ventilation specialist will identify the sources of condensation that are leading to mould growth and provide you with advice about the best way to deal with the problem for good.

Need help with condensation, mould or damp problems?

One of our local experts will contact you to learn more about your problems, offer free expert advice and make recommendations for a permanent solution.

During the free survey we will

  • check Assess any condensation, damp or mould problems in your property
  • check Take readings of the relative humidity levels
  • check Identify any underlying problems and make recommendations for a permanent solution

Arrange a FREE Home Survey now