Condensation problem on external wall in extension Damp can be a major issue in the home. Find answers to questions or post your own here.

[elliott111]

Hi all, i'm hoping that someone can help?

I live in rented accommodation which is basically a large house split into upstairs and downstairs. Before we moved in our landlord totally re-gutted the place, a new damp proof course was laid by a registered company as there was a damp problem and it was fully redecorated, new bathroom with extractor fan, all fully double glazed with trickle vents etc. We have been in for over 10 months now and everything is fine apart from we seem to have a condensation problem in the extension at the back (but only on one wall).

The landlord had the damp proof company back about 3 months ago to check that the damp proof course was working correctly which they confirmed that it was and said that it was a condensation problem.

I have tried all sorts. We have used dehumidifier which helps but is obviously not a long term answer if it is a problem. There is a large double window in the extension with trickle vents fitted and they are usually left on the latch for ventilation but it still does not make a major difference. The wall can be dry at time but i'd say 60% of the time there is condensation on it. The extension is built onto the kitchen and there is no door which obviously causes some condensation problems but we use cooker hood and also have windows open in kitchen when we cook which does help erradicate some of the steam issues. We have a condensor tumble dryer so there an no internal vents and we do not therefore dry on radiators. The bathroom door is kept shut at all times when we shower etc with the fan left running and trickle vents open.

I have looked outside the extension and from what I can see it seems like the wall is just a single brick/breezeblock thick? I don't know if i am correct in this assumption but from what I can see this seems to be correct. Could this be one of the problems. I don't know if there is a cavity in the wall. Can you have a cavity if the wall is just one brick thick? Would anyone recommend having cavity wall insulation to help combat condensation as it would keep the wall surfaces warmer? would it help?

My landlord is on holiday at the moment but is coming round on 9th Jan (he is a quantity surveyor in London so I am hoping that he will fully understand the problem). I just want to see if anyone has any suggestions? Would drying out the wall and insulating same and then erecting a stud wall make any difference?

All help/advice is appreciated!

Thanks

Elliott111

[stoneyboy]

elliott111,
If the extension is one brick thick then any rain hitting the outside of the wall will penetrate to the inside. Many people try to overcome this problem by applying render and/or paint to the outside of the wall. You may be able to limit damp penetration but you will never stop condensation. Building an inner skin with ventilated cavity is probably the only solution.
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[elliott111]

Hi Stoneyboy,

It is rendered also. I just find it funny that it is on only one wall?

[stoneyboy]

elliott111,
Rendering on its own will not stop damp renetration, you will need to either paint it or treat it with a silicone waterproofer.
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[elliott111]

My landlord has now mentioned about have the wall dry lined (can someone explain exactly what this is to me?). Will this combat the condensation problem? The wall is very cold to touch now and seems to be wet everyday!

[stoneyboy]

elliott111,
Dry lining is sticking sheets of plasterboard on the wall and making good the joins. Plasterboard with insulation on the back would be best but condensation will still form on the original outside wall and this can cause problems with water accumulating at the bottom edge.
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[elliott111]

Hi stoneyboy, my landlord came yesterday. He is going to put a foil insulation sheet on the existing wall and build a stud wall about 10cm away from the existing wall and insulate it then have it replasterboarded and decorated. Will this work?

On closer inspection of the wall he noted that the wall where the condensation is forming is the only wall in the extension which is single skin, the other 2 walls are brick and breezeblock with a cavity. He couldn't believe it!!! The extension was built before he bought the property years ago!

Thanks

Elliott111

[TheDoctor5]

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