Damp line along middle of interior wall

T

tvrulesme

Member
I've been slowly renovating an old 1800s listed building which was suffering from a lot of damp. I've managed to combat a lot of the damp in the house by installing French drains, fixing gutters, reverting to Lime plaster but there's one room which is completely throwing me and not sure how to move forward.

There is a damp line running along the centre of the bedroom wall which is an internal wall running at right angles to the exterior wall.

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Floor plan of the house showing the damp wall
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A picture of the exterior wall with the position of the internal wall. Internal wall butts up against the window at the right side of this picture

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Exterior ground levels are low. Gutters have been checked. Loft area above is dry with no leaks. Weather seems to make no difference. It's there when it's sunny and dry outside as well as when raining. Before decorating I removed the wallpaper which shows signs of previous works on what I assume were to combat damp

Damp line along middle of interior wall


Any ideas what investigation I should do next and what the likely fix would be?
 
A moisture meter will show how wet the wall area is and trace back to external end if readings higher there ?
Is external wall end brick work and window water tight ?
If no joy, hack off and tank the wall and replaster.
 
Smudger1 said:
A moisture meter will show how wet the wall area is and trace back to external end if readings higher there ?
Is external wall end brick work and window water tight ?
If no joy, hack off and tank the wall and replaster.
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Please bear in mind that I'm an amateur who doesn't know what they are talking about but wouldn't the cavity be designed to stop moisture from outside wall to inside?

Thinking about it, could it indicate a blocked cavity?
 
Check your window outside, it has no cill that goes out past the brick work the drip under the wood part of your cill cannot work because someone has siliconed across the front and if they hadnt the water will just sit on your brickwork and find a way in extend the wooden cill past the brick work and make sure there is a drip underneath
 
tvrulesme said:
Oh crap yes. Just looked at the brick pattern. Having said that I did find a cavity in the living room when I got heavy handed with knocking out a socket
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It looks to me as if the house has been extended a few times your damp wall although internal looks double skin, I'm going by the door opening
 
Any holes where this cable is clipped/ enters building - water can track through.
Your brickwork looks like header/stretcher bond - solid wall, no cavity. What lime have you been using?
 

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Mouldyoldspudgun said:
It looks to me as if the house has been extended a few times your damp wall although internal looks double skin, I'm going by the door opening
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It is double skin. TBH if the Listed Building info is correct, this part of the building has not been changed since it was built in 1800
 
Lastlaff said:
Any holes where this cable is clipped/ enters building - water can track through.
Your brickwork looks like header/stretcher bond - solid wall, no cavity. What lime have you been using?
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All clipped cables now removed and I had the plastic masonry paint removed to look for obvious cracks

Damp line along middle of interior wall


I haven't used Lime in this room because it was a bit of a gypsum mess and I was in a hurry so just went ahead. In other rooms I've used various. Ecomortar R50 and Secil Ecocork and Secil Cal AC mostly. Those rooms with Lime are dry as a bone now
 
Lastlaff said:
Hack off the plaster and see what’s happening below
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So I've heard hack off the plaster a few times. What is it exactly I'm looking for below? Damp? And if I find it what do you do then? Trace it back to the source. Clearly the previous owner must have had a crack at the damp before from the picture with the wallpaper stripped so I'm keen not to go nuts with no plan of attack
 
tvrulesme said:
So I've heard hack off the plaster a few times. What is it exactly I'm looking for below? Damp? And if I find it what do you do then? Trace it back to the source. Clearly the previous owner must have had a crack at the damp before from the picture with the wallpaper stripped so I'm keen not to go nuts with no plan of attack
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Rising damp does not exist ….

The remedial work is your problem
Remove (———-lime base lime top let it dry out add decoration.

Wakey wakey
 
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Dollar said:
Rising damp does not exist ….

The remedial work is your problem
Remove (———-lime base lime top let it dry out add decoration.

Wakey wakey
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No-one mentioned rising damp in this post so not sure what this is a reaction to.

I think we could assume that the previous owner would not have gone to the expense or trouble of trying to tackle the damp (however misjudged the remedial technique) unless there had been damp in the first place.

Hacking all of this off and redoing with Lime is dealing with the effect, not the cause. Yes the breathable Lime plaster will allow it to dry out more quickly and possibly the damp patch will go, but the damp patch would not be there unless there was a source of the damp in the first place so I'm really wondering what investigation I can do to find the cause of the damp. As I mentioned above exterior ground levels are low, gutters have been checked, loft area above is dry with no leaks, weather seems to make no difference.
 
I guess that external wall can’t breathe, paint on outside, tanking or something on inside going up nearly 2 meters. The internal adjoining wall also tanked (or whatever it is even just sbr) but only going up about 1 meter. the internal wall wicks the moisture out of the external wall or the ground (@Dollar lol) or both.
Is there a dpc?
then the heated room wicks the moisture out of the wall above the treated area on the internal wall as its the closest route for the water to get out into the air, as it is blocked everywhere else
 
Monkey Boy said:
I guess that external wall can’t breathe, paint on outside, tanking or something on inside going up nearly 2 meters. The internal adjoining wall also tanked (or whatever it is even just sbr) but only going up about 1 meter. the internal wall wicks the moisture out of the external wall or the ground (@Dollar lol) or both.
Is there a dpc?
then the heated room wicks the moisture out of the wall above the treated area on the internal wall as its the closest route for the water to get out into the air, as it is blocked everywhere else
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Brilliant reply. Thanks so much. So I think I have removed what I can of rubbery exterior paint. There's no DPC. I was wondering whether to put in a physical DPC on the internal wall as it would be fairly easy to do behind the skirting. See if it dries out and then go in with the hacking off/lime plaster once resolved to get rid of salts
 
This is a holiday home/midlife crisis so it's not occupied a great deal meaning there's very little human created moisture most of the time. The heating is also rarely on and the wall is damp when we've been away for long periods
 
tvrulesme said:
It is double skin. TBH if the Listed Building info is correct, this part of the building has not been changed since it was built in 1800
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To be honest I wouldn't take too much notice of the listing ours says we have a original seventeenth century bay window at the front with Georgian bars it's been repaired so many times the original has all gone. We also apparently have a original bread oven but apart from being built of symmetrical bricks and not hand made ones it's never been used.
 
I’d hack off all the plaster on the wall hose down the wall softly to clean it up and let it dry out for a few months, that’s your first port of call then you will see where the waters coming from . You could leave it brick too if it looks ok
 
Monkey Boy said:
I guess that external wall can’t breathe, paint on outside, tanking or something on inside going up nearly 2 meters. The internal adjoining wall also tanked (or whatever it is even just sbr) but only going up about 1 meter. the internal wall wicks the moisture out of the external wall or the ground (@Dollar lol) or both.
Is there a dpc?
then the heated room wicks the moisture out of the wall above the treated area on the internal wall as its the closest route for the water to get out into the air, as it is blocked everywhere else
Click to expand...
tvrulesme said:
Brilliant reply. Thanks so much. So I think I have removed what I can of rubbery exterior paint. There's no DPC. I was wondering whether to put in a physical DPC on the internal wall as it would be fairly easy to do behind the skirting. See if it dries out and then go in with the hacking off/lime plaster once resolved to get rid of salts
Click to expand...

Damp line along middle of interior wall
 
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