DIY Doctor

Damp patches, effloresence and blown plaster on interior walls

Postby mrkrunkles » Sun Aug 09, 2020 2:56 pm

On the interior of one of my exterior walls (which I 'think' is a solid wall) I have some quite bad damp patches, initially when we got the house we noticed that some of the plaster had blown on this wall and we had it replastered, but the plaster never dried fully and stayed in this quite contained damp patch (You might be able to see where I drew around the shape a while back and it hasn't grown/ shrunk much either way) we painted over it with some dulux and hoped the wall would 'breathe' and be okay eventually but clearly this is not the case.

wall01.jpg


I've now chipped off some of the damp plaster to re-examine the wall underneathe but I'm not sure of what I'm seeing. I do notice there's a good few screw holes that have been filled in, could these possibly be part of the issue? It's quite an old house with a painted outside wall.

There doesn't seem to be any obvious ways that water would be able to get in from outside, I'm at a bit of a loss of where to start with this problem, any advice from someone who's seen this before would be great.
mrkrunkles
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Postby stoneyboy » Wed Aug 12, 2020 9:01 pm

Hi mrkrunkles
The most likely issue will be with the painted outside. To stop damp ingress this must be a fully waterproof skin, cracks and fissures will allow rain to get into the brickwork and from there the only escape is inwards.
the concentrated area of damp may be linked to the multiple screw holes you have found - are there metal screws still in place, these may be providing a thermal bridge.
Regards S
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Postby mrkrunkles » Tue Aug 18, 2020 9:57 am

I will try to see if there are any screws left in the wall when I take back the rest of the plaster thats on the damp patch, the outside wall is painted with Sandtex Masonary Paint and there's no visible cracks I can see, would water still penetrate the paint?
mrkrunkles
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Postby stoneyboy » Wed Aug 19, 2020 8:31 am

Hi mrkrunkles
Suggest you run a hose on the upper part of the wall and see how much reaches the bottom, a bucket of water tipped on will do the same trick. Most should reach the bottom of the wall if it is not porous.
Regards S
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