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Damp-Proofing a Wall - Seal it From the Inside Using Damp Proof Membrane?

Postby nelianne » Thu Oct 30, 2014 11:22 am


We have a damp problem on the living room wall (this is also the gable wall), mainly showing through salts coming through the plaster and the paint bubbling off.

This has been attributed to cavity wall insulation; i.e. damp penetrating through the insulation on the wall. During the summer the outside wall was re-pointed and then sealed with a breathable compound. We also sealed the edges of the window, so the outside should be OK.

In the mean time, we also took the plaster off the inside of the living room wall (we were told it was polluted by the salts coming through). The wall is now ready to be re-plastered.

We have been told that (for added protection) we can use a liquid damp-proof membrane on the inside wall, before the base coat plaster goes on.

My question is; will this pose a problem in any way (sealing the wall on the inside)? Is this usually done, or is it more likely to cause additional problems?

Many thanks for any advice!
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Postby Pembrokephil » Sat Nov 01, 2014 5:32 pm

Sounds like the exact issue we have had. Did the damp appear after or before the wall was repointed? We had this problem after all the rain over last winter. Our insulation was put in 10 years ago and the wall repointed 4 years ago. We have had all the work covered by our insurance company as the wall was repointed before the damp. You need to contact them to see if you can claim. We contacted CIGA (Cavity Insulation Guarantee Authority - you should have their 20 year guarantee from the insulation installer) who paid for the insulation removal (there is a whole industry out there that does this!) and our insurers are paying for all the internal work. Our house is Edwardian so has a very early cavity wall and our insurers tell us that old houses should never have insulation installed. Happy to help further if needed.
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