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Many people write into our forum asking what causes damp in their homes

Signs and symptoms of Damp on internal walls

Causes of Damp

If you have a cavity wall there is a chance that damp on an internal wall is caused by a breach of the cavity.

This can happen for several reasons:

  • The gap between the walls has filled with rubbish and this is allowing moisture to travel from the outside to the inside wall
  • The Wall tie is covered in dirt or rust, so instead of any moisture dripping off the center of the tie, it runs along the tie and onto the internal wall
  • The damp proof course may have been breached – that is earth, tarmac or other material has been built up over the original damp proof course, or damp proof membrane, allowing moisture to travel along it
  • Pipework or other fixings that run through the wall have not been effectively sealed, so there is a direct route for moisture to travel into the building
  • Poor cavity wall insulation can also cause damp on internal walls

Diagnosing Damp

Symptoms you may notice are discoloured paintwork, black mould growth, flaking plaster, plaster ‘blowing’ or lifting away form the wall, or a white powdery substance caused by ‘salts’ leaching out of the plaster.

If you suspect you have a problem, you should use a damp meter to be sure that the area is actually damp, before taking further action.

Use a damp meter to test for damp on internal walls

Image courtesy of Property Repair Systems

Treating Damp

Treatment of the problem will depend on the cause, and so it is vital that you have found the cause of the damp problem before you start treatment, in order that treatment can be effective.

When we have lots of questions on a particular home improvement problem we write a project about it, for our project section to explain the causes and the solutions.

To find out more about how to diagnose and solve problems with damp in cavity walls please head over to our projects section.

If the problem you are experiencing is not covered in the projects section then do please place your query in our forum.

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