Chimney damp - losing our minds

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I've seen other posts on this forum in this vein but still need advice. We have been suffering with a damp issue related to our chimney stack. It's a 1950s house, hipped roof. The stack is quite large with two pots. All fireplaces in the house have been blocked off for years (by previous owners) so none in use.

Pic of stack:

PXL_20220216_113123291.jpg


Yes, I know we have copper flashing and that there is no lead tray in the chimney. Not visible in this pic are the clay cowls (with vent holes round edge) that now cap the pots. These cowls are sealed to the pots not just set in place.

Upstairs bedroom was reskimmed a year ago, still waiting to paint it and then just before Christmas during wet weather we saw this damp patch suddenly appear:

PXL_20231214_105628402.jpg


I looked in the loft and could clearly see water on timbers directly above this area:

PXL_20231214_145143724.jpg


Notice the damp on the rafter, as well as towards the base of the stack, in the image above. Now look at it during a drier spell below:

PXL_20240208_163141511.jpg


Everything there seems much drier. However, these areas do get darker looking now and again, roughly correlating with wet weather. And the damp patch in the room beneath now looks like this (see below). A bit drier in one or two spots but it is worse overall and has spread to the right though is much fainter in that area:

PXL_20240217_101828164.jpg


Our roof has six tile vents and also some lap vents I installed in a few places. In my (admittedly amateur) opinion, it's well-ventilated. I've only ever seen condenstaion up there on one exceptionally cold and foggy morning. I check regularly. But I suppose condensation could still be a factor here - I just would like to know if anyone spots something in these pics that I haven't!

We have been recommended to reflash, repoint and reflaunch the chimney and I am considering this because the pointing is clearly not great (there are multiple gaps visible in it). We are also aware that our ridge tiles need repointing and I wonder how much this could be contributing to our issue. (The damp timbers are really only apparent in this one area near the problem chimney stack, though there is a bit of staining here and there elsewhere in the loft. We actually have two stacks of the same design - only one is presenting issues at the moment.)

Some roofers, however, have insisted there is no way of fixing it and that the stack should just come down but I am unconvinced and suspect they are taking an easy option - these are people who in some cases have said they don't need to go up and inspect the loft or stack, they just know, categorically, it must come down. This seems ridiculous to me.
 
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If they don't go in the loft, it means they are not interested in a solution that saves the chimney. To be fair to the roofers, the brickwork looks pretty bad, so demolition and either cap or rebuild is a serious option. You complain the roofers don't look in the loft, then put up inadequate pictures for the forum to comment on. If you want to keep the chimney ventilate it properly, upgrade the whole of the chimney lead work including the back gutter, and chop out and replace any damp plaster with lime based. A lot of good trades use expert subbies or don't widely advertise, so keep an eye out for buildings where lead work is being done, or has recently been done, and you might get a recommendation and a name.
 
You complain the roofers don't look in the loft, then put up inadequate pictures for the forum to comment on.
OK. I'm aware the first pic in my post isn't high quality - apologies for that - I can't get onto the roof to get a much better shot. Hence why I've been asking roofers to look! I don't see how my photos on this post have anything to do with whether *they* do a good job or not.

To be clear, some roofers *have* made the effort and been helpful. I just wanted to explain that I am sceptical of those who haven't done this and immediately said removal is the only option.

I appreciate your advice, so thank you for that.
 
If it helps anyone, here is a photo of our neighbour's chimney - of the same design and condition. They have similar gaps in pointing.

I have tried to include all the detail I can, and everything I can think of to mention. If anyone has questions or requests for pics, if I can supply then, then I will. I am not trying to be unhelpful.

PXL_20231214_121657144.jpg
 
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Chimney appears uncapped? Which means rain will enter and not dry without ventilation, do you have internal vents on chimney breasts?
 
Chimney appears uncapped? Which means rain will enter and not dry without ventilation, do you have internal vents on chimney breasts?
The first picture above was taken before clay cowls were fitted. No internal vents, the breasts are on the outside and we do want to get some fitted to the exterior - brick vents or similar.
 
Copper flashing has gaps as not cut from single piece of copper. Covers are lapped up over rather than under the stepped flashing?
 
The first picture above was taken before clay cowls were fitted. No internal vents, the breasts are on the outside and we do want to get some fitted to the exterior - brick vents or similar.
Without vents you get damp in chimneys .
 
OP, Your photo number 4 shows the felt under the back gutter badly arranged & looking a bit sketchy.
Also, maybe moisture from higher up the roof has stained the rafters or the stains are from historic loft condensation?
You would need to lift the tiles around the stack especially above the back gutter.
And then lift the back gutter, & side flashings to see whats going on?
Photos should then be taken showing the conditions below and behind all the flashings.

No need to drop the stack. Photos of the flaunching and pots might help?
Have you read The Similar Threads below?
 
I just wanted to post an update here for anyone reading this thread in the future. We have not taken the stack down. A repair to the roofing felt appears to have solved the problem of moisture getting into the roofspace area around the outside of the stack.

The damp patch on the internal plaster has remained. I had someone do a calcium carbide test, which showed the plaster was dry (~3% moisture) therefore indicating salt contamination.

I'm currently weighing up options for how to deal with this. I know that it probably won't work but I'm going to try a shellac stain block to see if it can effectively seal in the salts and prevent the stain from showing. (I have also tried an acetic acid salt neutraliser wash but I'm not sure this has really done much). If the stain block attempt fails, I'll either have the plaster removed back to brick and re-done OR the skim removed in this area, a membrane added, and the whole wall skimmed over which might be less mess etc. This is the last room in the house to deal with, the rest of the house is decorated now so we want to keep disruption to a minimum.

If anyone has other suggestions for this please let me know.
 
I just wanted to post an update here for anyone reading this thread in the future. We have not taken the stack down. A repair to the roofing felt appears to have solved the problem of moisture getting into the roofspace area around the outside of the stack.

The damp patch on the internal plaster has remained. I had someone do a calcium carbide test, which showed the plaster was dry (~3% moisture) therefore indicating salt contamination.

I'm currently weighing up options for how to deal with this. I know that it probably won't work but I'm going to try a shellac stain block to see if it can effectively seal in the salts and prevent the stain from showing. (I have also tried an acetic acid salt neutraliser wash but I'm not sure this has really done much). If the stain block attempt fails, I'll either have the plaster removed back to brick and re-done OR the skim removed in this area, a membrane added, and the whole wall skimmed over which might be less mess etc. This is the last room in the house to deal with, the rest of the house is decorated now so we want to keep disruption to a minimum.

If anyone has other suggestions for this please let me know.
The salts may take many months to stop leeching out assuming the damp is resolved , if not it will continue.
 
Has the chimney itself been repointed also?
I suspect that unless that also happens anything further you do inside may be wasted when that leaks also.
 

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