Damp wall in converted chapel

[Carina]

Hi all!

We have recently bought a ground floor flat in a converted chapel (built mid 19th century).The building is the typical sort of stone chapels you find in Somerset with thick stone walls. It was converted into housing 10 years ago, and is in very good shape in general. However, one outside wall in the guest room shows some sign of damp, with paint pealing from a wall in a few places. The exterior of the wall in question never really receives any sunlight and the inside of the wall is very cold to the touch, there is also a quite substantial amount of condensation on that particular wall.

We've been told not to worry too much as the building is generally very well preserved, the outside walls don't seem to need repointing, and the problem is limited to only the one spot in the house. Of course, we are still a bit worried. This is our first house and we don't want to ignore a potentially serious problem. However, we've only just spent all our savings in order to buy the house and we can't really afford to spend a fortune on damp removal specialists at the moment.

If anyone can provide any sort of advise it would be greatly appreciated. Obviously we're considering getting a specialist in to check it, but we've been warned that they will always advise that work needs doing, even when it actually doesn't..

Kind Regards,
Carina

 

[Nemesis]

What sort of paint was used? The sort which supposedly 'seals' the building?

I suspect too that the pointing is cement, which may add to any problem.

 

[Gervase]

Aye, it has all the hallmarks of a wall which can't 'breathe' and which has the damp sealed in.
Stone doesn't take kindly to being painted with impermeable paints, or to being repointed with cement. As a first course of action, try stripping the paint - if you want a coating to replace it, use limewash, which is breathable.
That may fix the problem by itself - you'll need to wait a couple of months at least to see if it has.
If not, then you'll need to remove the cement pointing and repoint with a lime mortar.
it's worth checking your guttering and downpipes first, though, just in case there's a split or sag which is causing that wall to get a soaking.

 

[Carina]

Thanks a lot for the quick replies..

To be honest I'm not sure what paint was used, it doesn't seem too "plastic".. doesn't come off in strips or anything..
I can't quite make out what sort of render they've used, from the little bit of paint we've stripped away it is very smooth and cold to the touch.

What I just spotted and what concerns me a little is that on the lower ground floor there are two flats, more or less identical, around ours there is what looks like thin strip of cement all the way around the base of the property. The neighbours flat doesn't, so I'm assuming it has been added after the conversion.

With regards to the condensation on the wall, is it worth getting a dehumidifier to control the moisture in the air?

 

[Penners]

I can't quite make out what sort of render they've used

Aaah - is the exterior of the stone wall rendered? If so, then I wonder whether it's been rendered in cement. That, combined with the cement "strip" that you've mentioned, would certainly exacerbate the problem that Gervase has described. However, if I've misunderstood you about the rendering, then everything that Gervase has said still applies.

So long as the wall is unable to breathe, I'm not sure that a dehumidifer will give you any long-term solution. It could dry out the internal skin of the wall temporarily, but as soon as you stop using it, the damp will start to permeate again.

 

[Carina]

Right.. I seem to have confused both myself and others, so some clarification..

The exterior of the property isn't rendered/painted/anything, just exposed stone. What I probably meant is that I don't know what type of plaster or whatever they used on the inside wall

I think the point I was trying to make, when I somehow got lost was... Is it possible the wrong type of plaster would cause the problem? Or is it more likely it would be the paint covering the plaster/cement pointing?

 

[Mark]

the wrong plaster certainly wont help. I take it that the wall isnt dry lined? Just plaster (prob cement/gypsum) on stone walls ?
Condensation wont help either - some paints dont take well to condensation.

Have you checked all the usual things - gutters, ground levels etc?

 

[Carina]

How can you tell if the wall is dry lined? Sorry, I'm a novice when it comes to these things

gutters look okay as far as we can see, but we haven't investigated that fully yet (only recently moved in).

The ground level is roughly the same inside and out.

 

[Carina]

Just to give a bit of an update..

We stripped the paint as Gervase suggested, and after reading through some other threads on here we turned the heating on just ever so slightly, and have made sure to ventilate the room properly.

When we first stripped the paint off the wall there were several noticeable damp patches on the plaster that were darker than the rest of the wall.. A couple of days later and the damp patches are gone almost entirely! And the heating must have helped too because there are some areas we still haven'ts stripped, but there's no noticeable condensation anywhere anymore.

We'll follow your advise and try repainting the wall with breathable paint and take it from there.. Could it really be the wrong type of paint caused all that damp?!

Anyhow, thanks a lot for the help!

 

[Nemesis]

Breathing building, a bit of heat and ventilation - they are all much better and cheaper than most other solutions!

If you have recently moved in, has the building been recently converted?

 

[Carina]

Not that recently, done late 80s if I recall correctly.. I suppose it's just about long enough for problems with the way the conversion was done to start showing up..

 

[Penners]

How can you tell if the wall is dry lined?

Probably the easiest way is to whack it with the flat of your hand. If it's dry-lined, you'll get a hollow "boxy" sort of noise. If it's rendered or plastered masonry, you'll just get a completely dead, smacking noise.

Another possibility is to shine a light sideways across the wall - get the light as close to the wall as possible. If it's dry lined you might see hints of regular vertical lines about 4 feet apart. Depends on how well it's been plastered!

 

[Carina]

Definitely not dry lined then