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Damp Proofing

Still getting mould after installing 2 air bricks, humidifier & wall insulation

Anonymous user 28/02/2024 - 2.56 PM

Hi, we get mould on the corner of the bedroom wall (at low level on exterior walls) in a subground flat and am lost what could make a conclusive difference. Currently we have: 2 air bricks in that mold corner (one at mid level and other high level). Doesn't seem to change the humidity level when its above 0c outside. Interior wall insulation in that mould corner (1inch foam type wall paper) Read different sources in how to reduce condensation DeHumidifier that fills up within 8hours (only turned on during the night) Humidity sensor that averages 58%. When its below 0c outside the rating drops to 45% Radiator on the exterior walls under the window Humidistat fan in the bathroom which is opposite the bedroom Outside of the exterior mould walls have been checked by surveyor and respective repairs made Unsure conclusive next steps but am currently thinking: - Bigger radiator under window as the mould corner is the coldest part of the properrty - Heat recovery extractor fan - Double glazing property just to get rid of the mould Any suggestions/thoughts would be welcomed. Thanks for your help!

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2 Answers

JWSurveys Ltd

Rating: 5 out of 5

Hythe

Relative humidity is only part of the factor in calculating apparent condensation. You need to assess the air temp and relative humidity to obtain the "dew point" (the temperature at which condensation will occur) and then ascertain the surface temperature of the wall concerned. Bear in mind that this temperature will fluctuate and more than likely be at it lowest during the night when the heating is off etc. The air bricks, although a popular solution, will actually lower the temperature of the surrounding area, bringing it possibly down to the dew point. This is theoretical of course as I havent assessed the property. I note you have a humidistat fan in the bathroom. What is the RH setting??? Also is the kitchen vented??

Answered2 March 2013

Anonymous user

I have worked for a client who had a similar problem in their bungalow. We too had lined the wall with wallrock thermal but this didn't help as could still smell the damp. I asked if there was a drain oustide which there was. However, the problem actually turned out to be from when the property was built. The bricks when laid, the snots as they are refered to (I am a decorator so please excuse me!) were chipped off and these made tiny holes in the damp proofing. This was addressed by the client and the problem solved. This would only happen if the house is built with cavity walls. Does the corner have a soak away, how does the rain water drain away? It does sound like it is an external problem, may need to consider tanking and installing a dpm (damp proof membrane) if this has not been done.

Answered3 March 2013