Void in cavity insulation causing condensation ?
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NickT
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Void in cavity insulation causing condensation ?

by NickT » Sun Oct 23, 2022 5:32 pm

We have an area of wall just above the skirting board about 40 cm long that is damp to touch and has peeling wallpaper.
It's adjacent to a conservatory separated from the house by a bifold door. So I opened up a hole in the plaster board to check the cavity. Our 1930s house has foam cavity insulation (previous owner). And there's a cavity area with no foam roughly next to the damp area.
There's also a big draft blowing up from the 60cm air void under the suspended timber floor.
There is no sign of mould / dampness on the cavity side of the internal skin of bricks, yet the plaster is sopping wet in the room.
I suspect the cavity wall void is creating a cold spot and hence the condensation. It's got a lot worse over the last 4 years though. And we haven't had any major work done.
So I think the answer is to fill the void in the cavity insulation ..?
There's another damp area about 4 metres away on a dividing wall, but I guess same issue (though there's probably no cavity in a dividing wall I guess).
The picture shows the hole into the cavity where the insulation void is, the damp plaster and the dry looking cavity.
Picture of cavity void
Picture of cavity void

NickT
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Labourer
Posts: 2
Joined: Sun Oct 23, 2022 5:04 pm

Re: Void in cavity insulation causing condensation ?

by NickT » Tue Oct 25, 2022 5:09 pm

Spoke to a surveyor, they think my suspicion is correct, so will fill the void with some rock wool spare from the loft. (would prefer rock wool matt, but silly to buy 8m2 of it when I need 0.5m2).
then run a dehumidifier for a bit to dry it out.

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