damp alcove next to chimney breast

[SGray]

Hi all.
Our home is a cottage built of local stone and rendered outside with a (probably) concrete render (I'm not sure how to tell the difference between concrete render and lime render). It was built in 1807. We have spent the last two weekends removing bricks blocking an alcove to one side of our chimney breast. The wall that has been removed was modern and it has revealed the original stone walls of the cottage and what to our untrained eyes looks like mud in between the stone. There is dampness to be seen in the wall up to a level of about 2", and there are small traces of plaster (lime? - it has hair in it) to be seen on the stone so we know that it was once plastered. The base of the alcove has what looks like an original flagstone.
We have had a plasterer around to give us a quote. He suggests coating the stone with a cement render impregnated with SBR to give a waterproof coating prior to skimming. Can anyone see any problems with this approach?
We would like to put a cupboard within the alcove - are we likely to be asking for problems with dampness / condensation in the cupboard if we do this? How could we prevent dampness within the cupboard?
With regard to likely damp problems we are also unsure how to deal with the floor of the alcove.
I may be able to post some pictures if this would help.
I would be very grateful for any thoughts any of you may have.

 

[Gervase]

Using a waterproof render will simply trap the moisture in the wall. It will continue to be wet and when the render cracks (as it will eventually on a stone wall without modern foundations), the moisture will find its way out.
I can understand the plasterer's advice - he's used to modern materials, wants to do a quick job, and anyway, that's what everyone uses.
But it's the wrong approach for the house.

You probably don't want to hear this, but you need to remove the cement render on the outside. You should also check that soil levels outside are below your inside floor levels. Doing those things will allow the wall to 'breathe' as it was intended to do. Removing the cement render may mean that you hve to repoint the outside of the house (use a lime mortar) and if the wall is particularly exposed to the prevailing wind and rain, it may need a lime render.

What looks like mud between the stones probably is mud - earth was very common as a bonding material. I would recommend replastering with a haired lime plaster which will flex with the movement of the house, breathe and help control moisture.

With all the work, inside and outside, do not use cement or any 'waterproof' materials. These are designed for modern buildings which are engineered completely differently to houses with stone walls and no damp-proof courses.

 

[diamond]

We had a similar problem with our Cornish stone cottage which has an external cement render. Our alcove was enclosed by breeze blocks and very damp and mouldy inside. Just by letting the air get to it and repointing with lime mortar the damp problem disappeared - and has not returned after 2 years. My advice would be, if you don't feel like taking off the external rendering at the moment, try waiting to see what happens after repointing.

 

[SGray]

Thank you Gervase and Diamond for your reply.
Gervase - I love your philosophy and treatment of old buildings and I am worried about the condition of the external render to the house and part of me would love to say "yes that is what we are working towards" BUT removing the external concrete render seems like a huge job and something that we probably can't afford at the moment. (though I have no idea how much it would cost - any idea anyone?). Also, we did have a surveyor who came recommended to us as someone who knew about old buildings when we initially realised we had a problem with damp who didn't seem to be worried about the render externally. So I'm left wondering how important removing the external render would be and how much difference it would make?
Internally, the rest of the room seems to have concrete over the stone and then gypsum plaster over that - so is there any point in treating just one corner differently?
Also - if we put a cupboard in that corner wouldn't breathable lime plaster then cause a problem with damp in the cupboard?
The main idea of unbricking the corner was to give us extra storage (a toy cupboard - all of you with children will know exactly why we need one).
Diamond - when you say "repointing with lime mortar" did you mean internally? Is your external cement render still in place? did you plaster over the stone internally?
thank you again.

 

[Penners]

You say that this alcove is next to the chimney breast. Do you, or will you, use the fireplace that the chimney serves? If so, this could be of considerable help in drying out the dampness.

As others have said, I certainly wouldn't be happy enclosing the alcove to make a cupboard, as you plan, while it's damp. The contents would be likely to suffer. And a waterproof cement render will only be a short-term fix, as Gervase has explained. It will fail sooner or later.

Would you consider using the alcove for open shelves? Provided you didn't put anything in contact with the damp wall, this shouldn't be too deleterious to the stuff on the shelves. And it would give the damp wall a chance to dry out.

 

[MdB]

Sgray, our alcove had a cupboard fitted in it but had to be removed as it was very damp. The wall is stone + mud construction with cement pointing work on the outside. Inside there were at least 6 layers of stuff on the walls including two tanking layers of some type of black gunk. It may have worked for a while but trapping moisture in the wall is not a long term solution and isn't good for the wall. Damp mud is not as strong as dry mud. Currently all the old junk has been removed from the wall on the inside and the ground level outside has been lowered and it is going to be left for at least 4 months to dry out. We will then lime plaster the wall on the inside so that damp doesn't build up again inside the wall. It may be possible to fit a cupboard back into out alcove but there will be moisture build up which would require vents of some sort to be fitted. We didn't fancy this so we are going to fit shelves instead with a gap at the back so that air can circulate around them.

Hopefully this will solve the problem (it already no longer feels damp in the room) and I won't need to remove the cement from the outside of the wall in the short term though the plan is to remove it at some stage if easy to do.

 

[Gervase]

The thing about old buildings is that you don't usually need to to things in a hurry - so follow Diamond's advice and see how the damp fares with just the inside plastered. Give it a few months and you may find that it solves the problem and you have no further worries. In which case the render can wait until you win the lottery.
Do have a look at the soil levels outside, though, as this is one of the commonest causes of interior damp, and one of the cheapest to remedy.

 

[Gervase]

...sorry, that'll teach me to hit the 'submit' button before fully reading the post.
You say the rest of the room is cement render and gypsum plaster? You may find that this actually increases the damp in your alcove, as this now forms the only escape route for the moisture trapped in the walls. But note the may - buildings are contrary b*ggers, and don't always behave as hydraulics and thermodynamics would have you expect. Conversely, you may find that the alcove remains perfectly dry once you've exposed a big enough area for evaporation.
Suck it and see - you'll not be doing any harm at all by removing the breeze blocks and modern material that filled the alcove. And, if it does remain unacceptably damp for a cupboard, what about a curtain or a louvred door?

 

[SGray]

Thank you again for your responses.