damp patches on chimney breast wall

10 Nov 2009
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United Kingdom
We are still struggling with damp patches on the chimney breast wall downstairs and upstairs in a bedroom above the wall downstairs. They are always in the same place. We have had a chimney sweep to clean and check the chimney and all seems ok but the damp continued. Then we had a ventilating cowl fitted to the chimney but still we're getting damp patches.
At the bottom, the fireplace has been almost bricked up but there is a small rectangular hole that has been left which we have left open. A piece of furniture is in front of that hole but we thought we had left enough space for air to get behind it and ventilate.
So my question is ...should we move the piece of furniture or should be block the hole up altogether because I'm now very confused! It's a big piece of furniture ( a dresser) so we don't want to move it unnecessarily. Any advice would be much appreciated.
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Good morning Myra :)
Obviously it's a good idea to have any redundant chimney swept and nicely ventilated.....however, did the chimney sweep just survey the chimney internally or did he get onto the roof to inspect the condition of any lead flashings or flaunching (cement capping of the stack around the pot) and the pointing of the thing?
If you can access your loft space to see the chimney brickwork you may see any evidence of water ingress....my own is cement rendered and quickly showed a split in the lead flashing a while ago.
If you could give us a photo of the dampness position (without going to too much trouble) that could be helpful.
To be honest I'm a bit confused that the damp patches are so far apart.....damp in old hearths is very common and this can manifest itself with patches on the sides of the breast but on the first floor this has to be water ingress one way or another.
Another couple of questions.....how old is the property, approximately - and is the chimney lined where the problem is?
John :)
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Hi John:) Good morning to you too. So sorry to trouble you again but we've had this problem for so long and your reply caught us just moving the dresser that was in front of it so good timing for the photo. The sweep didn't go on the roof unfortunately but he took a video of the inside of the chimney which was unremarkable really. In the loft we looked at the chimney but it's brick and doesn't really show us a lot that we would recognise as a problem. A trained eye might see something. After moving the dresser we can see more damp which I hope you can see on the photo. However, there is no water at the bottom in the hole. Do you think it could be bad condensation?


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However, there is no water at the bottom in the hole. Do you think it could be bad condensation?

I certainly would not expect there to be signs of water, or you have a much more serious issue.

Personal opinion and not an expert....

If you can see the shape of the bricks in the damp marks, then it is damp most probably coming through from the chimney moisture.

If it is a much more general damp mark, then it is more likely to be a condensation issue.
Thank you Harry:), that helps because the damp is a more general shape so likely to be condensation then. So we've moved the big dresser that was in front of it (quite a task!) and hopefully it should improve.
Thanks again(y)
Curious, this one.....looking at the pic, the dampness appears to be where the fireplace lintel is, as if it was wicking water from behind it.
I guess the upstairs is a similar feature?
So, if the chimney pot has a rain cap on it, and the flashings and flaunching are in good condition I guess condensation could be the problem......somehow I'd doubt it as it does seem a little extreme. :(
John :)
Good morning John:)
I agree this is really weird and has been puzzling us for a couple of years now. The house was built in 1860 and as you know I am a regular visitor to this wonderful site because of its problems! The chimney breast is in a room with no direct window to the outside and next to a kitchen and close to a shower room . The fire place was taken out in the 1930s and had an old range in there when we moved in which had to be taken out. So we were left with a hole at the bottom about 9inches by 9 inches. We put a lovely old dresser in front of the wall to hide the hole and because it looked good so close to the kitchen. The patches started to appear and have been there for a couple of years at least but we thought they were getting worse. We tried everything and so then we had an inkling that it had to be condensation but, like you say, it seemed a bit extreme. So we decided to move the dresser after Harry's point about the shape of the patches (my back still hurts!) and the hole at the bottom then had a good air flow. We had nothing to lose but it was something we wanted to avoid. On the same day we thought we saw some improvement and yesterday there was even more improvement. This morning it looks the same but we're hoping for it to get even better as the week goes on. We are really grateful to you and Harry for such great advice and giving us the confidence to move the dresser and we have our fingers firmly crossed. Thank you!:)
If there used to be an upstairs fireplace as well as a downstairs one, they have separate flues, and both need to be ventilated.

It is quite common for builders to throw rubble into the opening or flue. This holds damp and should be removed.
Hi John:)
Separate flues?o_O We had no idea! So today we'll go up and move the furniture around and see if there's a vent because if there is then it's got furniture in front of it. Amazing ....thank you!
What JohnD says is absolutely true - each fire must have it's own flue, and theoretically a pot each at the top.
On occasion the flues met at the very top with thin brickwork called a 'feather' (which was prone to collapse :()
Myra, how did the chimney sweep clean the lower fireplace.....or did he not?
You could of course open your vents a little more and put a grille in place to disguise things a bit - if you are certain it is a condensation problem. I guess you'll see one way or another once the rain starts big time.
John :)
We can't see another chimney pot for upstairs so we're wondering what's happened. We're going to go up after lunch and investigate the situation by pulling the furniture out. Very strange!o_O
The sweep put a special brush up the flue and said it was very clean because I suppose it hasn't ever been used for a fire for many years. He also put a camera up to see if he could see any blockage but all was clear. Yes we'll see soon if it is condensation and I think if it is then it would be nice to have that vent made larger and maybe even stripping the wall back to brick completely as a feature wall. The wall paper has all bubbled up now with the damp so it would be nice to turn a negative into a positive.
It sounds like the chimney for your upstairs room has been capped after the pot was removed.....ideally there must be some ventilation up there - either with a terracotta terminal or maybe an air brick into the side, and of course a vent into the room as per the room below to keep some air moving.
If the wallpaper has bubbled, maybe the plaster beneath it is in a similar state?
Are these chimneys on an outside wall, Myra?
John :)

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