Polystyrene for Damp-Proofing?

Our daughter has moved into a converted flat. When I viewed the place with her I noticed there was polystyrene behind the wallpaper. The "builder" showing us round said: "Obviously thats there since we've cured the damp". Three weeks down the line the damp is anything but cured, their view is "Its condenstation", which reads like damp to me. Surely if a wall is damp the last thing you do is seal it in with something impermeable? If the damp was cured then why slap polystyrene on top?
BJ
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BJ wrote:

Could be a cold wall encouraging the condensation to form, so putting polystyrene is an attempt to insulate the surface from the cold wall, and reduce condensation forming on it?
It does depend whether the it really is damp or condensation though. Extractor fans in bathrooms, window open while cooking in kitchen, ventilation overnight in bedrooms etc all help reduce condensation problems. Keeping the place shut up tight can lead to very bad condensation problems cos the damp air doesn't dissipate before the next load is generated, and just builds up further and further. Damp needs the root cause finding and rectifying.
Velvet
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snipped-for-privacy@clara.co.uk (BJ) wrote in message

IMO it's not a totally unreasonable thing to do if the problem is genuinely condensation - what it does is reduce the temperature gradient between the moisture-laden air and a cold surface (if that's what you've got). Improving the air circulation would be a better solution though.
However, if you've got genuine 'damp' whether penetrating or rising (whether or not that exists!) then you're right - polystyrene sheeting or tiles are nothing more than camouflage.
David
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Thanks everyone, the landlord said it was condensation, and it is on an outside wall. Leaving the windows open in this weather is hardly an option though,
BJ
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The windows don't need to be wide open, just open a fraction all day if possible.
This weather would actually be good time to try it, we've got dry northerly winds forecast for several days, which should stop existing condensation and help dry out the structure of the building.
--
Steve


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