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What Kinds of Mould Grow on Walls

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What Kinds of Mould Grow on Walls

By Ruth MacEachern

Product Manager

Jan 09, 2024

During the cold winter weather, mould can become a more common sight in homes around the UK. In fact, around one in five British homes suffers from condensation damp that creates the ideal conditions where mould can grow.

What is mould and what are the risks

There are many thousands of different mould species that can grow in homes. Moulds are closely related to fungi, and a large colony of mould is made up of two main parts. The mycelium which grows beneath the surface and consumes nutrients and the fruiting bodies which appear as large dark blooms on the surface. The fruiting bodies are the most visible sign of mould and are how the problem spreads.

Mould spreads through microscopic spores that are shed by the fruiting bodies as the mould matures. These tiny spores can be inhaled or land on the skin where they can cause irritation and inflammation. Many people with respiratory problems or asthma can have allergic reactions to mould spores that include skin irritation, rashes, difficulty breathing and streaming eyes.

People with weaker immune systems can have more serious reactions to mould. Younger children and the elderly are particularly at risk of severe health problems from mould that can be potentially life-threatening.

What species of mould grow on walls

Mould spores are always present in the air, but not all species are able to grow in homes. The most common species of mould that grow in homes in the UK are Cladosporium and Alternaria. These types of mould are strongly associated with allergic reactions and can also cause mental health issues including depression and confusion if they are present in large quantities.

Stachybotrys Chartarum – also known as Toxic Black Mould – is less common but is more dangerous to health. In addition to releasing spores which cause allergic reactions, Stachybotrys Chartarum also releases chemicals called mycotoxins that have been linked to severe allergic reactions and a variety of medical conditions.

Cleaning mould from walls

Most moulds can be cleaned from the surface of walls using either dilute bleach or a special fungicidal spray. The chemicals should be sprayed onto the affected area and left for thirty minutes to allow them to kill the mould which can then be wiped away using a damp cloth.

When cleaning mould you should wear eye and mouth protection to prevent ingestion of the mould spores, and any cloths that you use should be disposed of after use to avoid spreading the mould to other areas of your home.

If you are prone to a reaction to the mould spores, or you suspect that toxic black mould is present, the mould should be professionally cleaned to protect your health.

Permanent prevention of mould

Unfortunately, simply cleaning mould away will not solve the underlying problem. The majority of the mould biomass is beneath the surface, and over time, the fruiting bodies will return.

To stop mould returning, you need to remove the conditions which allow it to grow. Mould typically grows in damp patches, so finding the cause of the dampness is essential. Rising damp occurs when moisture is drawn up into the walls from the ground because of a damaged damp proof course. You can identify rising damp as it is found on ground floor walls up to one metre above the ground. You may notice a stain or rotting skirting boards. Stopping rising damp requires repairs to the damp proof course.

Penetrating damp occurs when water is leaking into a property or escaping from an internal pipe. As with rising damp, penetrating damp is quite easy to find, as it will normally be close to the source of moisture – such as a gap around a window or a hole in the ceiling. Once the source of the water has been removed, the damp will start to dry out.

If there is no obvious cause of damp, it may be due to a build up of condensation on a porous surface. Condensation damp is caused by elevated levels of water vapour in the air condensing onto a surface and soaking in to saturate the underlying materials. Solving condensation damp usually requires improvements to your home ventilation to expel the humid air. Installing modern extractor fans in your bathroom and kitchen will remove most of the water vapour that is generated and prevent it escaping into other rooms. If you have condensation with no obvious cause, whole house ventilation may be more effective. Positive Input Ventilation systems such as EnviroVent Atmos feature a central unit that is normally mounted in your loft. This draws in fresh filtered air from outdoors to replace the humid air in your home.

Find out more

Finding mould in your home can mean a serious underlying problem and put your health at risk. Our local ventilation specialists can help. Book a free home survey in which we will identify the causes of condensation and mould and provide you with advice about the best solution for your needs. Simply enter your postcode below to find an expert near you.

Need help with condensation, mould or damp problems?

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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

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