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How to spot signs of damp

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Learn how to spot the common signs of damp and be ready to tackle it.

 damp on the walls

Signs of damp in a house

If a house is suffering from a damp problem, it means there's unwanted moisture and water inside or outside, in the walls, ceilings or floors.

A damp problem can occur for a number of reasons, including as a result of leaking pipes, broken or missing roof tiles, moisture rising up from soil or as the result of bricks that are porous. 

A small patch of damp on a wall initially might not seem too bad, but if it's not dealt with promptly, it can increase and cause numerous problems. Plus, it can affect your health too and exacerbate health issues such as asthma. 

Some of the common signs of damp inside a house include:

  • A damp and musty smell

  • The appearance of mould or mildew on walls, floors or ceilings

  • Walls, floors or ceilings that feel cold or damp 

  • Dark or discoloured patches on walls or plaster

  • Lifting or peeling wallpaper

  • Excessive condensation on windows

Damp problems are categorised according to type. Penetrating damp tends to move horizontally across walls or ceilings, whereas rising damp moves vertically up walls. 

Signs of rising damp 

If you're worried that rising damp could be a problem, there are some particular signs that you can look out for. These include:

  • Damp patches that start at the base of a wall and gradually move upwards, in a vertical fashion

  • Skirting boards or plaster that is damp or rotting

  • Floor coverings, such as tiles, vinyl or carpet, that are wet and lifting

  • Peeling paint or wallpaper

  • The appearance of a white, powdery salt-like substance on a wall

  • Yellow or brown tide marks or staining on a wall 

Rising damp can sometimes be tricky to deal with, or prove rather costly, so if you suspect it could be an issue, get it checked by a professional as soon as possible. 

Damp on outside walls

Damp can occur on interior and exterior walls. If penetrating damp is a problem, it's often due to structural problems, such as damaged guttering, roofing or cracks in the wall.

Old bricks can also become porous, which lets water in. As with internal walls, you might notice darker patches appearing on outside walls or, in the case of rising damp, dark swathes of tide lines rising up the walls.  

How to check for damp

To check for areas of damp in a house, carefully examine walls, floors and ceilings for any tell-tale signs. Feel for damp patches and peek under flooring that appears to be lifting.

In the early stages, the only indication of a possible damp problem might be a damp or musty smell.

If you suspect your house could have rising damp, a useful trick is to run your hands across the affected area. You should be able to feel the plaster salts – white deposits that are washed out of the bricks and into the plaster.

If there is wallpaper on the area, listen for a slight crunching sound as you move your hand over the salts.

However, the best way to check for certain is to call on the services of an expert surveyor. The surveyor will thoroughly check for any signs of damp inside or outside the property, identify what type of damp it is and the likely cause, plus offer advice on the best way of resolving it.

How to fix damp walls 

If you have penetrating damp due to porous bricks, replacing the bricks or painting them with a special exterior silicone water repellent paint can help fix the problem. Not all damp problems are easily resolved though and many involve the need for expert help.

For example, you may need to have a cavity tray replaced or added to stop water from the outside wall reaching the inner wall, have a new damp-proof barrier or course installed, or have internal walls or floors sealed in damp-proofing material.

An expert will advise on the best approach to resolve your damp problems and the costs involved. It's always worth getting a couple of quotes from different tradespeople before deciding whose services to use.

It can be a real worry to experience damp in your home, but to help reduce the risk of your property suffering from a damp problem, keep your house well maintained and promptly deal with any problems that arise.

This is especially important as damp problems caused by poor maintenance aren't covered by home insurance.

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