Condensation - advice required please


19 Oct 2009
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United Kingdom
Hi All,

I need some advice on a condensation problem. I moved into a 1950 built house in spring. Over the last month as temperatures have fallen condensation is forming on the inside walls above window height in the upstairs rooms.
There is no condensation on the windows, all of which have vents that are open. Extract fans in bathroom and kitchen are used and washing is not dried indoors.

On investigation I noticed the outside brick wall stops at soffits level and the boards sit on the bricks. I’m assuming the inside layer of bricks of the cavity wall carries on above this level for the last 18 inches to ceiling height. I’m assuming this part of the wall is single brick.

Is this a common build method and is there a way of insulating this part of the walls?
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Its a standard detail with the inner leaf rising past the outer leaf.

Insulated plasterboard would work well but you'd have to do the whole wall to overcome a perculiar high level detail inside.

You can insulate this soffit area but it depends on how your roof void is ventilated.

If you have a breather membrane roofing felt or no felt/membrane then the soffit ventilation is not so important so you could introduce some insulation here - ensure there is a 25mm gap below the roofing membrane.


If you have a non-breathable felt then the soffit ventilation is crucial and should not be blocked. A 50mm clear ventilation path MUST be kept clear to allow cross ventilation of the roofspace.

Which have you got?

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