Crumbling damp plaster query

#1
Hello! I'm new to the group - I have done a plastering course (more than happy to skim walls) but won't be tackling this particular job myself. I have a house here in Cornwall, with 2ft thick granite walls that have recently been lime pointed (about 3 years ago). The wallpaper in one of the bedrooms started to lift from the walls in places, and there has been some staining leeching through (attractive!). I have removed all of the wallpaper today and the old plaster is bubbling in places and is wet in others. I have checked the guttering and downpipes and there's no leaks onto the walls. I've been up into the attic and there's no loose tiles or water ingress. I also air the room regularly. What could be causing the wet walls? Would it be best to hack the old plaster off and get lime plaster on the walls? Any ideas? Thanks!
 

vfr12

Well-Known Member
#5
If there is no other source that cause it , yes, alternatively you have to find it and deal with it. What lime have been used for pointing and what dept? You have done the wall favour already by removing the wall paper. A picture from outside will be more helpful than from inside .
 
#6
If there is no other source that cause it , yes, alternatively you have to find it and deal with it. What lime have been used for pointing and what dept? You have done the wall favour already by removing the wall paper. A picture from outside will be more helpful than from inside .
I would say you have a debris trapped between back of lath and outside wall
 

irish_spread

Private Member
#7
Sorry - I didn't realise that it hadn't uploaded. Here you go:
View attachment 27887

Can't tell from limited info and 1 pic. Probably best to get a local specialist to look at it. But from that pic alone it looks like black mould which happens in areas where there is no air circulation plus covered in wallpaper. If you can see salts on the wall the 1st thing to do would be to brush them off at the very least as these will absorb more moisture and get worse.
Was there furniture in front of that damp area before you discovered the damp ?
 
#8
vfr12 - here's some shots of the external wall. I'm not sure what lime was used but it was done to a depth of about 4".
irish-spread - there was no furniture in front of the wallpaper but that wall does get the worst of the Cornish weather, although I'm not sure if the cold difference would have increased the damp.

Think I'll get someone in to look at it but thank you for your comments so far. Much appreciated.
 

Attachments

#9
that pointing looks first class mate. is it lath and plaster inside
 

vfr12

Well-Known Member
#10
if that corner is at the bottom of the rain pipe, check your drainage. Most likely you killed the wall with the wallpaper and underneath you have hot lime, oh boy, I love quick lime, in which case it’s a hack off for me.
 
#13
if that corner is at the bottom of the rain pipe, check your drainage. Most likely you killed the wall with the wallpaper and underneath you have hot lime, oh boy, I love quick lime, in which case it’s a hack off for me.
The photo is in a bedroom - we get loads of rain but the downpipe drains freely so I don't think it's that. Best I get my finger out and hack the plaster off then!
 

vfr12

Well-Known Member
#14
The photo is in a bedroom - we get loads of rain but the downpipe drains freely so I don't think it's that. Best I get my finger out and hack the plaster off then!
And don’t put any wallpaper! Let it breaaaaaaaath .
 
#15
go to worst area and flick off plaster with a screw driver to reveal lath and see if choke up behind lath after all the work on outside ithink a lot of vibrations may have broken the key between the laths causing it to fall and get stuck very common thing
 

vfr12

Well-Known Member
#16
And when you do that pay attention to the plaster and the wall . Will tell you where the moisture is coming from.
 

vfr12

Well-Known Member
#17
Is it a solid wall ? We never got the answer.
 

vfr12

Well-Known Member
#19
My guess is solid wall. The typical no ventilation syndrome, but the wallpaper.... made it cry :D
 
#21
just wish he would tune in and tell us
It's about 2ft thick granite walls. I think you may have a point about the ventilation - it was ventilated but can get extremes of temperature in the winter which I guess must have contributed to the problem.
 

vfr12

Well-Known Member
#22
It's about 2ft thick granite walls. I think you may have a point about the ventilation - it was ventilated but can get extremes of temperature in the winter which I guess must have contributed to the problem.
Not only. My guess, again, is that the lime inside is not up to the standards and you’ll do your self a favour replacing it with lime putty, not nhl.
 
#23
I have no idea how old the plaster is in there but I'm guessing a few decades old - it's also been glossed at some stage so that would trap in any moisture too. Thanks for your inputs!
 
#26
Where did the lathing plaster come from ? , thought it was solid granite walls ? Solid granite is obviously cold and can definitely cause mould problems inside. Warm air inside condenses on cold external walls.
In Cornwall you'll probably have local lads experienced in lime plastering, get their advice.
The guttering and downpippes are new, as previously mentioned, query historical leakage