There are many types of mould, but they all require moisture to grow, and the process can be accelerated by creating an optimum environment, which is what this article will discuss.

In order for mould to grow in your home, it needs the following:

  • Moisture – this is typically caused by water leaks and poor ventilation after hot showers.
  • Mould spores – Mould is produced by spores, which are invisible single-cells capable of growing without sexual fusion. They’re airborne, and commonly found both outside and inside.
  • Food – Mould feeds on dry walls, wood and cotton.
  • Darkness – mould cannot grow under UV lighting.
  • Warmth – mould can’t grow in freezing temperature, so warmth is required.
  • Oxygen

That list may seem odd, because the majority of those elements exist in every home, so every home sounds like a breeding hive for mould. In reality, the primary reason for mould development is moisture, because it’s the one element that can be controlled, therefore able to prevent mould from growing.

Mould will find it extremely easy to grow in damp conditions. So ultimately, if you’re home is being attacked by any form of mould growth, it’s most likely because you have a moisture problem somewhere.

Common reasons for mould growth

Poor ventilation

This is probably one of the most common reason for my mould develops in the home, especially in kitchens and bathrooms, because there is generally a lot of steam generated in those rooms. Steam and water evaporating into the air creates humidity/moisture. So if either of those rooms are poorly ventilated, mould will generally thrive.

Poor ventilation also means wet surfaces take much longer to dry, especially in bathrooms, where there’s a lot of water being used.

Plumbing leaks

Leaking pipes and taps are also common reason for mould growth, that’s why you often see mould develop around sink taps.

Unfortunately, leaks are often left neglected, especially if they’re not causing enough of a nuisance to warrant getting fixed. However, what most people don’t consider is that it’s encouraging mould to grow, so it’s better to get any leaks resolved immediately, regardless of how small it is.

Another problem with leaks is that they can often go unnoticed, especially when they’re under a sink or inside a wall. By the time the problem is discovered, mould has already started to grow.

Roof leaks

If you have mould on the ceiling, particular on the floor which is directly below the roof, there’s a good change there’s a leak in the roof.

Much like a plumbing leak, if you have a loft, leaks in there often go unnoticed until it’s too late, because lofts aren’t frequently entered, and when they are, much time isn’t spent snooping around, so leaks are almost never spotted. However, it is a good idea to frequently check for leaks in the loft if you have one.


Humidity around the home can be created both naturally and artificially.

A natural cause of humidity is the weather. If the weather has been humid for a few days, it can easily cause mould growth. Also, when it rains quite a lot, it’s common for mould to grow on walls and other surfaces due to the moist air.

Some parts of the country are also just naturally high in humidity, especially areas by the coast, where there’s a lot of moisture in the air. Many homeowners in these areas use dehumidifiers to combat the problem, as opening the windows allowing for ventilation won’t do much good.

An artificial method of creating humidity is by drying wet clothes inside the house. This is further discussed below…

Wet clothes

It’s amazing how many people don’t realise how potent wet clothes can be when they’re left to dry inside the home.

Drying clothes indoors (e.g. on the radiator or left to hang somewhere) is a common cause of humidity. But also, mould can actually grow on the clothes and the surface around them if they’re left wet for too long. Damp clothes left in a pile can lead to growth mould in as little as one day.

Damp basements

Basements are extremely prone to mould growth, and that’s because they’re not very well ventilated, meaning they’re usually moist/humid. Moreover, many basements don’t have heating because they’re not lived in areas, so they’re often colder, which means more condensation occurs which leads to dampness and humidity.

Another reason that makes basements prone for attack is the fact that any water leaks from above levels will often end up dripping through to the basement. Basements are very similar to lofts in the sense that they’re rarely visited, so mould infestations and/or leaks often go unnoticed until damage has already been caused.


If the air is moist and it makes contact with a colder surface (e.g. walls, windows or mirrors), the moisture condenses into water droplets, which is what condensation is.

Condensation is usually present on bathroom mirrors and windows after a hot shower/bath, and it’s directly associated with mould growth.

In many cases, condensation may only occur certain times of the day, so mould growth maybe the only sign of a condensation problem.