What Causes Damp on Internal Walls? – Causes and Solutions

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what causes damp on internal walls

Damp on internal walls can be a big problem. As well as being unsightly, damp can cause mould to grow. This has been linked to asthma and other health problems. So, exactly what causes damp on internal walls? And how can you treat it?

There are a few different causes for damp on internal walls. The source of the moisture can be from condensation, leaky pipes, rising damp, or penetrating damp. The important thing is to diagnose the problem that is causing the damp on your internal walls.

Importance of Identifying the Type of Damp

Treatment for damp patches on your internal walls will depend on the type of damp that you have. Before you can start actually fixing your damp problem, you have to diagnose which type it is. Each type of damp has different symptoms and each is letting water into your wall in a different way. You can’t treat damp on internal walls unless you know what the source of the problem is.

Below are a few ways that can help you identify the source of your damp.

Ways to Identify Condensation on Internal Walls

Condensation is one of the most common sources of damp on an internal wall and one of the simplest to fix. Condensation on internal walls is caused by hot moist air building up. This air can’t escape a room, so hits a cool wall and turns into condensation. This moisture can soak into a wall, which might be what causes damp on your internal walls. These are the signs you should watch out for to see if condensation is the source of your damp:

  • Visible condensation – Condensation can actually be visible on your wall. Look for small dew drops or obvious moisture.
  • Where it is –  Which of your internal walls has damp can help you see if it is condensation or not. Condensation is most likely in rooms with a lower temperature or poor ventilation. If your internal wall is colder than the room on one side, it’ll be an easier target for condensation. Bathrooms and kitchens have more moisture so they’re vulnerable.
  • Furniture – Condensation is the main cause of damp behind furniture.
  • Humidity – A humidity sensor can help you quickly figure out how humid the room is. Although this might be overkill if you have other symptoms.

To treat condensation, you’ll need to reduce moisture in the room. You can do this by improving air circulation. You could consider using a decent dehumidifier. Learn more about that here. Finally you can stop damp and mould returning by  applying a good anti mould paint.

Ways to Identify Penetrating Damp

Penetrating damp is a problem where water enters through your walls. The moisture usually finds its way in via defects in the brickwork, soaking into your internal walls and becoming damp. Below are some symptoms of penetrating damp:

  • Paint and plaster – This will be flaking off and becoming damaged where the damp is coming in.
  • Damp patches in specific places – Penetrating damp will be coming through your wall in patches that don’t start at the ground.
  • Water – If penetrating damp gets really bad, you might have water coming through the visible damp patches. 

Treating penetrating damp can be a bit more difficult. This will usually involve fixing external defects such as broken bricks or damage to things like pointing, or external render and paint.

Ways to Identify Rising Damp on Internal Walls

Rising damp is a type of damp that can affect internal walls by pulling water up from the ground. This is similar to penetrating damp; Water is still traveling through the brickwork. However, rising damp travels vertically rather than horizontally. Also, instead of an external defect it is usually caused by a defect in the damp proof course.

Below are some signs you can look for that would indicate rising damp is your problem:

  • Skirting boards – Moisture from rising damp will be drawn from the ground up. Skirting boards becoming damp or rotting is a clear sign that this is the type of damp.
  • Damp tidemarks and peeling wallpaper – Like with other forms of damp, rising damp will cause peeling paint and wallpaper. This will usually be low down starting above the skirting.
  • The spread of the damp – Rising damp spreads upwards and across the wall. It will start lower, and the tide mark will gradually progress up the wall. If this is what has been happening, then it is the cause of the damp on your internal wall.
  • Salts – Rising damp can lead to salts pulling up from the ground which turns into a white powdery substance on your wall, this will often be clearly visible on the tidemarks. 

To fix issues with rising damp you will need to repair or replace the damp proof course. There are several DIY solutions for this such as damp proof course injections.

Ways to Identify Leaks from Pipes and your Roof

The last probable source of damp for your internal walls is from issues with pipes and roofing. This type of damp can often get overlooked compared with the others, so it is important to check this out. Below are some signs to look out for:

  • Visible damage – For a roof or chimney defect the most obvious symptom is going to be visible damage. This type of damage will usually be in ceilings and the tops of walls in the upper floors of your property.
  • Becomes worse in rain – Roof problems will often get worse when there is rain, since more water is being let through the defect. 
  • Close to pipes – If your damp is caused by a pipe leaking, its likely to be contained to the area around the pipe. Check if the damp seems to follow where something like a radiator pipe might be.
  • Floors – A leaking pipe will release water that eventually soaks into the floor as well as the wall. A wet carpet near the damp spot might mean a leaky pipe is to blame.

Fixing damp from defects like pipes and roofs is often as simple as taking care of the defect itself. Fix any problems with your roof, walls, or pipes that are causing the damp. You will still have to treat the damp patches that are there already, and waterproof the wall against future damp.


If you’re wondering what the cause for a damp internal wall is, it really depends on your specific symptoms. What is important is finding out which type of damp you have. Check your walls and figure out whether you have condensation, rising damp, penetrating damp, or if the damp is caused by a defect. Once you figure that out, treating the damp itself is going to be a lot simpler.