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Why Do I have Damp Patches on My Walls?

The Most Common Causes of Damp on Interior Walls

If you have discovered a damp patch on a wall in your house, it is crucial to find the cause of the dampness as quickly as possible to prevent the problem from getting worse and also to ensure that it does not develop further into a more serious mould issue that could be bad for your health.

There are three leading causes of damp in homes, and while they all result in a similar effect, the action that you need to take will depend on the type of damp problem that you have.

The different types of damp

Three main types of damp can affect your home:

Penetrating damp is where moisture enters the house through a gap and soaks into the plaster of your walls.  It may be due to damage to a roof or a hole developing around a window frame, or it may even be coming from a leaking pipe from your heating system.  Penetrating damp is usually relatively easy to spot.  Because the water is soaking through the wall, it will become discoloured, creating an evident stain around the damp patch.  The cause of penetrating damp will usually require you to get some professional help to solve the leak and then potentially replace any affected plaster.

Rising damp will usually be found on the ground floor of buildings where there is a problem with the damp course – either it has become damaged or has not been installed.  Rising damp creates a tide mark about one meter above the ground, caused by water being drawn up into the wall from below.  Rising damp can be expensive to repair and will usually require a builder to install a damp-proof course in your walls that acts as a barrier to the moisture being drawn up into the walls in future.

Condensation damp is caused internally when moisture from the air forms droplets of water on cold surfaces and then soaks through into the wall.  If it is not treated quickly, condensation damp can easily lead to the growth of mould.

Dealing with condensation damp

Condensation is when water vapour in the air turns into liquid water. This occurs when warm, moist air comes into contact with a colder surface, such as a window, wall, or floor. When this happens, the moisture in the air condenses and forms droplets on the surface.  One of the most common places for condensation in a house is on walls, which is a common cause of damp patches. This can happen for a number of reasons.

The main cause of condensation in homes leading to damp is high humidity levels.  Humidity is the amount of moisture in the air, and high levels are typical in homes that do not have proper ventilation.  Condensation occurs if the air is not able to circulate and the moisture is not able to escape. Activities such as cooking, showering and drying clothes indoors all contribute to the amount of moisture in the air in your home.

Condensation damp is typically worst in colder rooms without good airflow.  Insufficient insulation can make the problem worse. If walls are not well insulated, they can become cold, creating conditions for the air's moisture to condense and form damp patches.

Preventing condensation from causing damp patches on walls

Several steps can be taken to prevent condensation from causing damp patches on walls. One of the most effective ways to prevent condensation is to improve ventilation in the home. During the summer, this can be as easy as simply opening windows and doors to allow the air to circulate, but to deal with the problem all year round; you need to ensure that you have installed adequate ventilation in wet rooms such as the kitchen and bathroom.

How ventilation reduces condensation and damp

Extractor fans in bathrooms and kitchens work to reduce the amount of moisture in the air where it is most likely to be produced and prevent it from escaping into other rooms.  The fan will usually be mounted high on the wall or at ceiling level on an external wall and positioned opposite from the door.

The extractor fan should run while you use the bathroom or kitchen and for around 30 minutes afterwards.  Modern extractor fans, such as the EnviroVent Cyclone 7 have moisture sensors that adapt the power level to reduce humidity as quickly as possible.

If you have discovered damp patches elsewhere in your home, poor airflow in those rooms may be allowing condensation to form.  In such cases, whole-house ventilation systems such as EnviroVent Atmos may be more effective.  Positive Input Ventilation systems (PIV) like ATMOS work by drawing air into the home through a central unit which is usually mounted in the loft.  The air drawn in by this central unit is then fed into different rooms around your home to displace the humid air and prevent it from causing condensation.

Find out more

If you are concerned about the damage that damp could do to your home or the health risks that mould could present if it is allowed to develop, it is essential to deal with the underlying problem as quickly as possible.  Improving your home ventilation can stop condensation and damp for good.  Enter your postcode below to book your free home survey.  Our local ventilation experts can visit your home, identify the causes of condensation damp, and advise you about the best solution.

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

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