Arrange a Survey

The Causes and Effects of Mould in Your Home

Select a category

The Causes and Effects of Mould in Your Home

By Ruth MacEachern

Product Manager

Apr 30, 2021

Finding patches of mould growing in your home can be concerning, and your first priority will be to clean it, but it is also important to understand what the cause of the mould growth is so that you can take action to prevent it returning in the future.

Mould is unsightly, but in some cases, it can be harmful to health. While the spores of many household moulds are allergens that can trigger asthma attacks, there are some species of mould including Stachybotrys chartarum (also known as toxic black mould) that release mycotoxins – poisonous substances that can cause severe reactions in some people.

What is Mould?

The exact number of unique mould species that exist on earth is unknown and may be more than a million – although only a small number of these are common in British homes. 

A mould is a type of fungal species which grows in the form of thin filaments called hyphae.  These Hyphae spread across a surface as a network which is known as a mycelium.  A patch of mould is, in effect, a single organism.

Because the filaments that make up a mould patch are so thin, the mycelium is white.  The colour of mould comes from the spores which are shed from the ends of the filaments all the time – these can be almost any colour, but the ones you see most often in homes are usually green, brown, or black.

Moulds can grow on almost any porous surface and are often seen on food.  The most common types of mould that may be found growing on walls or wood surfaces in houses are:

Black Mould (Stachybotrys chartarum) this species thrives in rooms with a lot of moisture such as bathrooms and kitchens.  In the early stages of its growth, it can look like a dusty patch, but is usually slightly wet to the touch.

Altenaria usually grows in darker areas such as in damp cupboards under sinks.  Like many moulds, it tends to do best in the warmer and more humid summer months.

Aspergillus grows in dusty environments where there is moisture.  It is common in plasterboard but can also grow on painted surfaces.

Cladosporium tends to colonise softer surfaces such as wood or fabrics and creates patches that can be difficult to spot until the spores start to form.

What Causes Mould to Grow

Mould grows best in damp conditions.  In houses, this is usually in corners where condensation can soak into surfaces.  Mould spores are part of the dust in any house and can start to grow very quickly.  In the right damp conditions, a mould patch can develop quickly and spread across a wall where it will be clearly visible.

What are the Effects of Mould?

There are two main risks associated with mould.  The spores of most household moulds are allergens that can irritate the lungs and airways when inhaled.  People with asthma can suffer from more severe symptoms and the damp conditions associated with mould can also trigger respiratory problems in otherwise healthy people.

Some moulds, such as toxic black mould release more dangerous chemicals called Mycotoxins into the air.  These are harmful to both animals and humans and can lead to serious illness if inhaled.

How Can Mould be Removed?

Mould can be cleaned away relatively easily.  A mixture of 1 part bleach to 4 parts water can be sprayed onto the mould patches and then they can be wiped away.  You should ensure that the area being cleaned is well ventilated to the outside of the house, and it is important to wear a mask, eye protection and gloves when cleaning mould to avoid inhaling the spores.

Although mould can be cleaned, it will grow back as long as the damp conditions it relies on remain in the house.

To prevent mould, you need to reduce the amount of condensation in a property.  Ensuring that you use pan lids and extractor fans when cooking, close doors when bathing and avoid drying clothes on radiators can help reduce the amount of condensation that can form in your home, however, to remove the problem altogether, you will need to improve the ventilation system that you have.

Good ventilation prevents condensation by removing humid air from the house before the moisture it carries has a chance to condense on a cold surface.

Find Out More

Mould can be a major health risk if not treated quickly.  To find out more about reducing condensation damp in your home and preventing dangerous mould from growing, please contact us to arrange a free home survey where our local ventilation specialist can assess your needs and provide advice about the best solution for you.


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