Mystery damp, or….?

[BlueTed]

Hi All,
I have a mystery damp problem and I will give some background.
The house is an old house and historically there has been a leak in one alcove adjacent to the chimney breast. This alcove is in the middle of the house with no outside wall, and the right hand alcove (facing the road) is dry. The chimney itself (exterior only) was removed many years ago and there is a lead gully between my house and next door and this gully runs above each alcove and across the capped off chimney. It might be worth mentioning that next door is a Victorian property and mine is Georgian, and the gully was added when the Victorian house was built.
18 months ago the roof was re-tiled and the gully replaced with a new lead gully.
When it rained the old damp patch got slightly damp again, but ever so slightly and there was no running water. The roofer could not understand it because he took the new gully back up and it was bone dry, he looked in next doors roof space, again bone dry, and looked in the attic rooms above the damp patch and it’s all dry.
Is it possible that the old blown plaster and area of damp can attract moisture when the atmosphere is damp?
The attached images show how the old wallpaper has been hanging for a couple of years, and the second one is when I pushed the wallpaper back up. It follows that in the summer, the whole area dries up. The damp area is the glue of the paper and this had not been touching the wall for the past 18 months so the only way moisture could have got onto it is in the atmosphere.
Apologies if I have not explained things very well - and I will be grateful for any thoughts.

 

[a twig]

No rogue water / heating pipes in the vicinity?

 

[malcolm]

Still some water getting in there. It's got to be either leaky pipes or roofing issues.

 

[BlueTed]

No rogue water / heating pipes in the vicinity?

It’s an interior wall directly joined to my next door neighbour (but not a party wall as my house was built about 100 years before theirs).
It’s dry either side, and it’s dry above so it’s a mystery.
The only thing left could possibly be splashback from the gully but this was taken back up after it was renewed to check for leaks and it was (I’m told) bone dry.
I guess I’ll just have to get the new builder to have a look and see if he can find anything. More expense after paying £20k for the retiling and new gully!

 

[BlueTed]

This is the gully mid roof works, after the new gully was installed and before the tiles were hung.
The small humped part adjacent to the lifted slates (next door property) is where an old chimney was removed many years ago. The damp patch is directly below this hump and the farthest end in the photograph. If you imagine the hump as the chimney breast in the room it is the left hand alcove when facing it.
There was a leak here for many years and I (perhaps blindly) thought the new gully and new tiles would make it all watertight…

 

[a twig]

Ha haa- does your gulley definitely flow the right way?

Ours didn’t and all the water used to back up against the closed end, overflow the lead and permeate down through the wall into the corner of the room below.

Got ours re-done at great hassle and expense but solved everything.

 

[BlueTed]

Ha haa- does your gulley definitely flow the right way?

Ours didn’t and all the water used to back up against the closed end, overflow the lead and permeate down through the wall into the corner of the room below.

Got ours re-done at great hassle and expense but solved everything.

I hope so! It does slope away (if you zoom into the photograph) but it’s a possibility that the parts either side of the ‘hump’ are not steep enough. I think the gully was over £1k so it’s irritating to think it might need more spending on it after being there for 18 months (and the leak/damp) has been there all along!

 

[Drayton]

If it is an historic leak and only mended 18 months ago is it possible it is still drying out, downwards, slowly? How thick is the wall and how wet was the whole lot was originally?

I'm asking as places on some of my walls still seem to be sorting themselves out a couple of years after extensive repairs, which makes sense as I have 2ft sandstone rubble walls.

More specifically I had a patch of damp very similar to yours on a chimney breast which appeared to dry out a little but then at least seemed to get wetter just as I was about to decorate (of course, though maybe I was just looking at it more closely). There didn't seem anything in particular to fix, it looked dry above, which was very odd as it was wet right from the top of the room for a fair distance along, then down half the wall, like yours. A year later it has tar/salts staining, very much the same as the one on the other side of the house, but no longer looks damp. I'd forgotten how bad it had been until I came across a photo the other day.

We have had a ridiculous amount of rain this autumn, mostly gale driven, but it hasn't recurred. I considered condensation but presume that should have been more consistent (and a hbit less wet)

(I will, of course, go upstairs now to find I have a wringing wet wall again )

 

[BlueTed]

If it is an historic leak and only mended 18 months ago is it possible it is still drying out, downwards, slowly? How thick is the wall and how wet was the whole lot was originally?

I'm asking as places on some of my walls still seem to be sorting themselves out a couple of years after extensive repairs, which makes sense as I have 2ft sandstone rubble walls.

More specifically I had a patch of damp very similar to yours on a chimney breast which appeared to dry out a little but then at least seemed to get wetter just as I was about to decorate (of course, though maybe I was just looking at it more closely). There didn't seem anything in particular to fix, it looked dry above, which was very odd as it was wet right from the top of the room for a fair distance along, then down half the wall, like yours. A year later it has tar/salts staining, very much the same as the one on the other side of the house, but no longer looks damp. I'd forgotten how bad it had been until I came across a photo the other day.

We have had a ridiculous amount of rain this autumn, mostly gale driven, but it hasn't recurred. I considered condensation but presume that should have been more consistent (and a hbit less wet)

(I will, of course, go upstairs now to find I have a wringing wet wall again )

How interesting. My grandmother owned the house before I bought it and although I have a recollection about various leaks in different rooms, I never paid much attention. I seem to recall that this might have been a leak which was ‘fixed’ (or most likely ‘bodged’ by a builder who would do odd jobs) and for a year before the roof was retiled it was the same as it is now, but a bit damper and more noticeable when it rained.
Fast forward the roof works, it’s not as bad as it was, but it’s still not bone dry!
What is much more frustrating is not knowing what the cause is. Perhaps something very simple that the original roofer missed. It’s just infuriating to think how much money the house needs and I’ll potentially being throwing quite a bit more at this one leak. Oh well, what can we do - old houses