Does penetrating damp cause mould? And how to fix it?

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Mould is an unpleasant problem to have in your home. It can destroy decorations in your property and there are even potential health implications.

Not only that, but it can be quite embarrassing when friends and family visit and they are greeted with patches of back mould on walls and ceilings.

does penetrating damp cause mould

Ideally, when you do find mould you should remove it and deal with the route cause, so the problem does not return. This will require you to identify the type of damp causing your issue.

Damp issues such as rising damp and penetrating damp can cause mould growth. However, they only represent 15-20% of mould cases in the UK. This also includes many other internal issues, such as burst pipes and leaking roofs.

The remaining 80-85% of damp cases are caused by condensation.

The main reason for this is simple. Things like penetrating damp are just less common than condensation.

The average household can produce between 15-20 litres of water every day. This comes from household activity such as bathing and cooking. As well as human bodily functions like breathing and sweating.

If condensation is the issue, then you can take some measures to reduce the moisture content of air in your property. A few things you can do include:

  • Opening windows and doors to allow better ventilation and air circulation.
  • Try to avoid indoor activities that cause large amounts of moisture, such as drying clothes indoors.
  • Use a dehumidifier to extract excess moisture from the air.

These simple tasks will help to remove excess water vapour in the air. This will result in less surface moisture in your property and will mean mould has less chance of starting to grow.

How do you know if penetrating damp is causing mould?

The next most common type of damp after condensation is penetrating damp. This describes any kind of moisture that is entering your property (penetrating) from outside.

Penetrating damp will usually happen via defects to the outside of your property. This can include things like:

  • Cracked and damaged bricks
  • Issues with pointing between brickwork
  • Damage to external renders
  • Water running onto your property via faulty guttering or down pipes.

Penetrating damp tends to be easy to identify. It will have a different appearance to damp caused by condensation.

Generally, penetrating damp will be visible as damp patches on your internal walls. These may be visibly wet and can often get worse when it rains.

In most cases you will be able to figure out the possible cause of penetrating damp, by examining the area outside adjacent to the internal damp patches.

Penetrating damp can be the perfect environment for mould to form and start to spread. This means it should be rectified as soon as the damp is discovered.

Also, by fixing the external issues sooner rather than later, you will avoid any potential long term damage that this type of damp can cause to your property.

How does penetrating damp cause mould?

Penetrating damp, or any other type of damp do not actually cause mould. Instead they provide the perfect environment for mould to grow and spread.

Mould thrives in warm moist locations and it is very adaptable. Meaning it can grow on many surfaces in the modern home.

All mould really needs to thrive is a decent level of humidity and moisture. As well as a source of nutrient to feed on and grow.

Suitable nutrients can be found in many of the materials that are used in property construction. So, mould will have no problem growing and spreading in a property, if the conditions are suitable for growth.

Penetrating damp usually causes wet patches, and this is ideal for mould growth.

How does mould spread?

A common way most types of mould spread, is via releasing spores. These spores are generally not visible to the human eye.

They can be spread through the air, via water or moist surfaces and they can even hitch a ride on humans and pets. If they manage to settle on another nutrient rich surface, with moist warm conditions they will start to grow and form new mould patches.

In particularly damp properties, this spread can be quite significant over time. If mould is left to its own devices, it can result in a kind of snowball effect, where mould starts to thrive and cause real problems in a property.

How can you stop mould?

To stop mould, you simply need to make the environment less suitable for it to grow.

The only way to do this, is to remove moisture and reduce humidity to between 30-50%. We already mentioned a few things you can do to stop condensation previously.

If on the other hand, your problem is coming from a defect, such as penetrating damp or rising damp, you will need to solve the root cause of the damp issue. This will involve fixing any defects and stopping water from penetrating your property.

In some cases, you may be able to use DIY damp proofing solutions. However, it is often a good idea to have a damp specialist check your problem.

The advantage with a professional, is they will be able to pinpoint the exact cause of damp and offer the best recommendation to solve the problem.

Finding a local damp proof expert is quite easy by searching online. One of the best places to look is on comparison sites, where the companies have ratings from previous customers.

Our favourite comparison site for damp experts is called Bark. They have lots of highly rated damp professionals and will put you in contact with up to 5 local experts.

Most damp experts will come out and diagnose your problem for free. Or in some cases there may be a small call out charge.

Click here to view profiles of local damp experts


Mould can be a nuisance in your home. It can be cause by a variety of different situations. The most common is condensation.

However, problems like penetrating damp can also provide the perfect breeding ground for mould.

Whatever problem is causing mould, the key is to remove the conditions that are needed for it to grow. This means removing moisture from the air and surfaces in your property.

If you remove dampness and humidity you will make it much harder for mould to grow and spread.