Thank you for this. It follows the same line of thoughts as me. With the fireplaces blocked there would be no natural vents and there are no air bricks anywhere. The double glazing is at least 10 years old so no trickle vents and everything I touch seems to have been blackjacked instead of solving the problem to start off with. Obviously none of these problems showed up in the surveys because it had all recently been updated. I know why now. Must check on U values.

you could have a rising damp issue if its the room is located on the ground floor, old house , natural stone walls , which have absorbs water other the years, you will need a 4 inch hole with a ventilation grill covering it to let the room get ventilated it could just simply could be the room need ventilation, i agree with katie , get a building surveyor to survey your property, you could save money and time

I don't think taking off the old plaster is going to help as the damage is being caused by the blackjack. I think i'd probably recommend a dehumidifying system in each room, you can vent in to the loft and put vents in the ceilings.

Obviously the Chimney could be looked at, but one of the above systems would hopefully cure the condensation regardless of the state of the Chimney.

We see this situation all too often where i live, there are a lot of old houses, that have been rendered and the bricks can't breathe, the moisture stays in the lime mortar and the only escape is back in to the rooms.

Here are a couple of links:- Ventilating Systems

Breathing space ventilation systems

I fitted one of these recently for a customer of mine, and he informs me that it's working well.

Also, be advised, that it is likely the moisture will take months not weeks to leave the bricks and mortar even after a ventilation system is fitted.

Thank you for your comments. The room is an upstairs bedroom so it's not a rising damp problem, I think I have one of those in the dining room where the paint was flaking and we have found more blackjack. I can't a fit ventilation system as we have no loft space, the roof just raps around them and we struggled to get any insulation up there will any sort of air gap. Shall try and investigate whether the chimney is completely full of cement so that an air vent can be placed there once the cap at the top has been broken up.

There is water getting in somewhere, and if it's not the walls then it could be the Chimney. Putting any vent in the room - through the wall to the outside will help dehumidify, but as the water shouldn't be coming through the walls, you need to identify where it is coming from. Are the walls rendered on the outside? are there cracks? My guess it's the Chimney!

In any event a vent through the wall will help cure the condensation, but you do still need to identify where the water is getting in from. You can buy 'silent' electric vents now. Such as these:- electric vent

Which wall did the plaster pop off, as clearly that's the wettest one!??

It popped of the external wall. The wall outside is painted and needs redoing. Living nearly 800 ft above sealevel and getting winds from the coast everyday the wall takes a real bashing and although there is no cracks highly visible, it wouldn't surprise me if something was getting through. I still think the chimney too.

I agree, with the outside wall, you only need tiny cracks, the water just builds up to saturation point and then comes out where it can. I'd still get the Chimney checked, but meanwhile keep the window open as much as you can ( not easy in the winter ). Get it all checked out before putting the vents through the walls, i;'d hazard a guess that there are cracks on the outside wall allowing water penetration, if that's where the plaster came off.

Check the Chimney a common source of water as it gets in through cracks where the Chimney meets the roof, if that's on an outside wall, it won't be helping.

Let us know how you get on.

This looks like a fairly good site to explain how it should work. http://www.jackinthegreenlime.co.uk/insulation.html

It is about finding a happy medium, but please don't cover it up. Sorry for multi posts am quite passionate about older building.

Thank you for your comments. The article you posted was really interesting and pretty much sums up what is going on with the house. The downstairs floor are concrete and blackjacked as they have obviously taken up the flags, They are also uneven so will have to get taken up to level out. I'm hoping there isn't 10 inches of concrete but even so it's going to be difficult to take out. This has pushed water into the walls, so they then blackjacked the bottoms of those and this has pushed the water higher. If only any of this was present when I bought the house I won't have bought it. The builder they recommended that had done all the works was supposed to be a member of the Federation of Master Builders, but I remember looking him up when problems first started arising and he wasn't listed. We have started stripped all the plaster from the external wall and the room is starting to get drier already. The walls are no longer sweating. I'm trying to work out what is under the blackjack. It doesn't look like plaster and I'm wondering it they have put some sort of cement based render on the stonework. Either way it's all going to have to be done correctly now. Bye Bye Bank Account :-(

Hi, Glad to help. I know damp problems can cause a lot of stress, especially if they are treated incorrectly and become worse after spending money on trying to resolve them! We have been working on Victorian solid wall houses for 20 odd years and I only now fully understand how it all works through our latest training. Your house has no doubt been like it is for many years, but understanding whats happening takes the stress away and then you can address it when you are able. Internal ventilation is also important, making sure you take the moisture you are producing out. Do you have Kitchen extractor fan, bathroom extractor fan and some trickle vents in the bedrooms? Opening windows and creating a cross draft has the same effect, but you have to be mindful and remember, also its a bit cold. Have you got any pictures of your place? would be good to see it.

We have a similar issue where there's an external chimney breast thats been blocked off at the top. It causes large damp patches to come through to the spare bedroom. We're saving up to have the chimney removed all-together and then new external render applied but in the mean time used two coats of this super thick/sticky damp proof seal paint :

https://www.amazon.co.uk/Ronseal-OCDSW250-Coat-Damp-Seal/dp/B008VQ6RDY/ref=sr_1_4?ie=UTF8&qid=1484564742&sr=8-4&keywords=damp+proof+paint

Once its dried you can just use a normal paint over the top. I know its a completely temporary solution but its worked very well and the wall doesn't feel at all damp now.

Just a quick update, the plaster is being taken off the wall upstairs and while some it is coming off easily, there are other more stubborn parts. As the wall seems to be rendered with some sort of cement render I thought I have a look under the plaster board wall downstairs where damp marks kept appearing. Wellllllll, what a hack job they have done now there. The stone has been taken out to the middle core and in someparts the wall is held up by breezeblocks. They have obviously sold the stone as it would have been faced and now its just one big giant mess. Think the damp was the least of my worries and I'm really not sure how to go about dealing with a stone wall fulls of patched uneven cement, holes and breezeblocks. How I envy those people who find architectural gems hidden under stud work. Errrrr

While I would normally agree with you the house wasn't converted until 1996 and the neighbours have already told us there was a fireplace in that room which is now blocked up. There was also polystyrene tiles behind the plasterboard which indicates it was done recently. The huge granite keystone is still in the corner but has tool marks on it so you can see they were trying to get it out but thought otherwise hence why I feel they sold the faced stone. It also came up in the searches that they had applied for a demolition order so they could build 5 houses on the land and it was turned down. If you wanted to knock something down you would take everything sellable out. As for what to do now I'm not sure. The wall is not behaving like a stone wall should because it is now just one side and it's core. I need to check what's going on with the chimney because that how far they have taken the stone off.

So after having some builders around today the feedback is, to either tank the whole room and put plaster board back in, or to put a solid wall back in to replace what was taken out. The chimney is full of rubbish so needs to be cleared out. The only other alternative is to build an Extension further out and then take this wall down as they feel it might be too damaged. Oh the problems. A little less stressed out now that I know it's not about to fall down if I touch it, just miffed that someone could damage something that would have been nice and would have stood up there for some time working perfectly well without interference. Thank you for all your comments though. At least I know Im not the only person that stuggling with these issues.