What is Mould?

Mould is the common term for fungi. A microorganism which includes approximately 300,000 different species. It will show on surfaces as patches of black, green, brown, yellow or pink. Often accompanied by an unpleasant, lingering odour.

What causes Mould?

Mould spores are invisible to the naked eye and float through the air. Growing when a spore lands on a moist surface, preferably in a dark place. To grow, mould needs mould spores, a food source (eg. wood, plaster, cotton), darkness, warmth, and oxygen. Excess moisture is the key contributing factor for mould growth as the others are usually always present in a building. Whether that be your home or place of work.

It is important to remember that a certain degree of moisture will always be and should be present in the air. For year round comfort, it is recommended that humidity levels sit circa 40%. Too much or too little can have a significant impact. Not only on your health, but the health of the building too. There are various ways to increase and decrease humidity levels. A damp and moisture survey can help you identify the current humidity levels within your property.

But how does excess moisture get into the air in my home / place of work?

There are several ways that excess moisture could be getting into your home, or even your workplace. The four most common types of damp include rising damp, penetrating damp, damp caused by defective plumbing and damp caused by condensation.

Rising Damp

Rising damp occurs when the water on the ground level rises up into the house or building. Having bypassed the damp proof course – a layer of waterproof material in the wall of a building near to the ground.

This form of damp will not usually rise above 36 inches from ground level. Therefore it usually only affects basements and ground floor rooms. With the trademark of a “tide mark” low down on the wall, rising damp often leaves a white mark. This is a result of the salt contained within the water.

Mould does not usually accompany rising damp as the salt prevents it from growing. However, if left untreated, it can cause other issues such as cracked plaster and lifting wallpaper.

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Penetrating Damp

Found exclusively on external walls and ceilings. Penetrating damp is caused by water passing through a building defect such as a missing roof tile or pointing. It will be most evident after rainfall and will appear as an obvious damp patch. This will dry out as the weather improves.

As the water can pick up salt as it passes through the building material, mould will rarely grow as a result of penetrating damp. Much like with rising damp, if there is any salt present, this will stop the mould from being able to grow.

Defective Plumbing

Whether it’s a leak from the toilet, shower, sink or a pipe, defective plumbing can affect internal walls and ceilings. Appearing as an obvious damp patch, damp from defective plumbing will appear no matter the weather outside. However it may get worse after a certain utility is used. Such as the shower is turned on or the toilet is flushed.

Although rare on larger leaks as the area will be too wet and waste water is generally poisonous to mould, it can appear if left untreated. Rot in wooden joists and floorboards is also a risk of leaving a plumbing defect untreated. Which, in severe cases, can lead to them collapsing.


The most common cause of mould is condensation. Water which collects as droplets on a cold surface when humid air is in contact with it. Think of those cold mornings when your heating is turned on and how much water is sitting on the surface of your windows. Condensation is most commonly found on or around windows. Especially during the winter, but also regularly grows within the corners of a room and on north facing walls. It can even be found behind large objects such as beds and wardrobes. In areas that do not get much ventilation – especially when up against an external wall.

There are many contributing factors to condensation and many are a result of lifestyle. From simple actions such as boiling a kettle or drying clothes indoors, there is a lot that we do every single day that adds to the amount of moisture in the air.

Mould is almost always seen with this type of damp and is often the hardest to remove as the cause (ie lifestyle) is not usually adjusted once the mould has been removed, resulting in it returning again and again.

If you want to get rid of mould, first you have to get rid of the excess moisture.

In part two of our blog, we look at condensation in more depth and the ways you can help prevent it.

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