24 Mar 2010
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United Kingdom
hi there, wouder if someone can help.

i've got a nasty-looking patch of efflorescence on the wall of my c.1910 terraced house and I'm trying to work out what has caused it.

The wall in question is a loadbearing solid (ie not cavity) brick wall between the living room (suspended timber floor) and kitchen (cement screed). Both sides are plastered and painted. The efflorscence is on the living room side, and other the other side there's a radiator.

The worst bit (see pic) is about 8cm across and about 70cm from floor level. There's a surrounding patch of slight discolouration where further blisters are developing.

Causes.. Because of the radiator on the other side of the wall, my first thought was a plumbing leak. However, the water pressure hasn't significantly dropped. Can I rule out a leak?

The other, more sinister cause might be damp of some kind.

What can I do to find out the causes and work out what kind of remedial action is required?

thanks in advance,


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having read around a little on these forums, another possibility occurs.

Could it be condensation caused by warm, moisture-laden air from the kitchen (possibly boosted by the rad) coming into contact with the colder, drier air of the living room?

Is there a way of establishing whether or not this might be the culprit?

And what could I do to eliminate the problem?

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looks like you're outnumbered there, freddiemercurystwin ;)
& with a surname like bulsara, isn't it a case of pot vs kettle?

anyroad chaps all this japery doesn't help my efflorescence does it now?! :LOL:
We've just done a bit of digging and found a couple of photos taken in Oct 2009, just after we moved in. They show the affected area had for some reason been infilled with cement (!). I think our decorator just skimmed over the surface.

Does this illuminate the situation?
I'm no expert on efflorescence but would think the chances of getting efflorescence inside are pretty slim.
Efflorescence is commonly found inside, usually where walls are subject to moisture whether that be damp, water ingress or even occasionally, condensation. As you have now pointed out that it is on a patch of new render, it is likely there was some sort of problem previously that has hopefully been sorted.
Check the outside wall for any signs of cracks where rain/water could be penetrating and working it's way to that point. If all is well, you should be able to scrape away the efflorescence to the bare surface and apply a coat or two of alkali resistant primer. This will stop the salts in the cement escaping and hopefully solve the problem, just remember that it won't work if there is still a moisture issue within the wall. ;)

I had a terraced house c1910 & the plaster was bowing off the wall in exactly the same place as your photo shows. I had a damp survey done & it was damp, at the time council grants were on the go so I had it treated by injection method, central heating fitted & all was well.

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