Identifying & Understanding Mould
It’s important to be able to identify and understand mould in your home. This guide answers essential questions like “what does mould look like?” and “what causes mould?”, so that you can protect yourself and your property. Learn how to recognise common types of mould and their effects on your health.
What is mould?
First, let’s explore what mould actually is. This will help us to understand how we can prevent mould in our homes and in work environments. You may have wondered, “is mould a fungus?” and you would be correct. In fact, mould is a common type of fungal organism that can live on plant and animal matter. That can include building materials and household objects, such as wood, plasterboard walls, carpets, curtains, and even books and clothes.
Mould grows in damp and poorly ventilated areas, spreading by producing airborne spores. These spores can reproduce easily in damp environments, both indoors and outdoors. Moisture control and ventilation are central aspects of controlling and minimising the growth and spread of mould in the home.
What does mould look like?
It's important to be able to identify mould in order to protect your health and home. It can appear “fuzzy” and look like a stain, smudge or discolouration. There are various types of mould - which we can look at in more detail - but you may be familiar with the most common black, green or white strains. Appearance and colour can vary based on age or life-stage. When recognising the beginning stages of mould in your home, you should look out for furry growths, black stains or unusual specks of colour.
Types of Mould
As we learned in the previous section, mould can grow in a variety of colours, including green, black, white, orange and blue. Some strains are more dangerous than others, and a single type of mould can grow in an array of colours depending on environmental circumstances. This can make it hard to identify exact strains, so it is generally advisable to remove any kind of mould to prevent spread and potential illnesses.
The most common household strains are the black and green varieties.
| Mould Colour and Description | Example of Mould Appearance | Possible Strains | Commonly Found |
|---|---|---|---|
| Green mould, which often looks “fluffy” |  |
Cladosporium, Aspergillus, Penicillium | Can be found in many houses in the UK, especially in bedrooms. Often grows on damp walls, inside cupboards and carpets, and on damp fabrics and mattresses. |
| White mould, which can look “furry” especially on damp wood. Appears similar to efflorescence (dried salt crystals) - differentiate between the two by spraying water over them. If the residue does not dissolve, it is white mould |  |
Cladosporium, Aspergillus, Penicillium | Often found in cool, damp environments such as in basements and cellars. Can usually be found growing up a wall. |
| Blue mould |  |
Penicillium (commonly expansum) | Common household mould, usually found in wetter rooms like bathrooms. |
| Black mould, which has a stain-like appearance and grows in spots |  |
Stachybotrys chartarum, Cladosporium, Aspergillus, Penicillium | Sometimes found in soil and grains, but most often detected in damp or water-damaged buildings with cellulose-rich building materials. |
| Yellow mould, which can often be mistaken for limescale in bathrooms. Has a dry, flaky appearance |  |
Aspergillus (commonly flavus) | Commonly found on seeds and nuts, but can also appear in homes and wet environments. |
Remember: Mould strains can vary in colour and appearance. Best practice is to aim to remove and prevent any mould that you find in your home or workplace. Although some strains are more dangerous than others, they can all have negative effects on your health and damage the structure of your property.
What causes mould?
Damp and mould are caused by excessive moisture. This can be influenced by poor ventilation, leaking pipes, damp in basements or on ground floors, and by rain if your roof or window frames are damaged. Mould can also be found in newly built homes, if there is insufficient ventilation or if the building is not fully dried out. In most cases, prolonged condensation is to blame for mould growth. Black mould is especially associated with condensation issues.
For more information about types of damp, check out our guide page here.
Can mould make you sick?
All strains of mould can impact your health if allowed to grow and spread in your home. Health effects can vary and some individuals may not be affected at all. However, young infants, elderly people and those with weakened immune systems are more at risk of sickness. Some strains are more dangerous than others. Nevertheless, identifying types of mould can be challenging, so all signs of fungal growth should be addressed promptly to avoid any of the associated symptoms of ill health.
As mentioned previously, mould is a fungal organism that produces airborne spores. These spores can enter your system and may be responsible for negative health effects, both in the short term and long term.
So, across different strains of mould you may experience various symptoms of ill health. Mould can affect some people more than others, depending on individual factors such as age and overall physical well-being. The main short term symptoms to be aware of are similar, regardless of the mould strain. If you’re worried about mould in your home making you sick, be proactive in ensuring that your environment is dry and well-ventilated. Consult a healthcare professional if you think that your health has been impacted by damp and mould. You can read government advice about understanding and addressing the health risks of damp and mould.
Dangers of mould in bedroom
As outlined above, mould can have mild to severe effects on human health, regardless of where it is located in your home. However, if you have mould growing in your bedroom, it could mean spending a large amount of time exposed to spores overnight.
Mould in your bedroom may also impact your sleep quality. Many of the short term respiratory effects of airborne mould spores could throw off your sleep rhythm and affect the overall quality of your rest. It is best to remove mould from all rooms in your property, but especially in rooms where you spend extended periods of time (or where you need to sleep).
How to deal with mould in my home?
It’s important to effectively deal with mould in your property or workplace, so that you can prevent spread and limit negative health risks. To learn about how to prevent and remove mould, you can read our guide page here.
For technical information about how mould can affect construction, read our guide page here.