Help! Damp patches on top of wall but dry in the loft :( *pic*

Mark A

Mark A

Mark A

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Hey guys,

Just been ripping the old council wallpaper off my walls ready to put lining paper up, then paint. When I ripped the paper off in the corner of the room and above the chimney breast, there was damp plaster and what looks like salt residue. The plaster behind the skimmed area has white powdery substance present and the plaster is coming away in areas.

There has been a damp patch on the plaster ceiling next to the chimney breast for years, it never gets any bigger but keeps coming through the paint. I believe the council remedied this and it was something leaking on the chimney stack. But I didn't know there was damp on the walls.

Been up in the loft and had a good look around and the chimney stack is bone dry with no signs of any damp.

The strange thing is that the wall with the big damp patch on stops in the loft and the bricks are visible from above and are dry. So water cant be soaking down :confused:. I just cant work out why its there or where its coming from.

Also, its the same in the next room, there is an airing cupboard and the paint is all shrivelled and flaking off.

tl;dr - walls damp yet bone dry above...wtf?

DSC_1041.jpg


Anyone got any ideas?
 
On our flat roof for the dormer, right next to the chimney, Seagulls build huge nests. This seems to hold water making everything damp and we did have damp on the inside of the chimney breast in an upstairs bedroom.

The foxes always take care of the eggs, but every year there is a massive nest I have to go and clear off.

So something is blocking the run off, and jBuk says, check your guttering.
 
it never gets any bigger but keeps coming through the paint.
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mould eats paint , the white residue is mould/mildew get some mould/mildew cleaner and clean the area before you paint over it.

you obviously need to fix whatever is causing the damp though , does it get worse when it rains? possible leaking pipe?

does the airing cupboard seem moist?

cant see any *pic* btw , okay i see your pic whats on the otherside of the wall?
 
arknor said:
mould eats paint , the white residue is mould/mildew get some mould/mildew cleaner and clean the area before you paint over it.

you obviously need to fix whatever is causing the damp though , does it get worse when it rains? possible leaking pipe?

does the airing cupboard seem moist?

cant see any *pic* btw , okay i see your pic whats on the otherside of the wall?
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On the other side of the wall there's an airing cupboard and the wall isn't damp but the paint is all flaking off.

Just been on the phone to my dad and he said it could be 'efflorescence' which seems to fit the salt on the walls etc.

Above that wall is nothing, it stops in the loft and supports the timber ceiling joists. So I cant work out where the water is coming from. Unless its coming from next doors.

Would knocking the plaster off and tanking it sort it do you think?

The only other thing I can do is have a look at the chimney stack to see if the flashings are damaged. But surely if that was the case the chimney stack in the loft above the damp area would be damp?
 
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Mark A said:
Been up in the loft and had a good look around and the chimney stack is bone dry with no signs of any damp.



Anyone got any ideas?
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Chimney stacks by their very nature are very rarely dry when measured for moisture with equipment like a protometer. They can feel dry to the touch but the chances are they will have some level of moisture in them. Hire a dehumidifier for a week and keep the doors and windows closed and see if that makes a difference.

Are there any pipes in the airing cupboard?
 
Mark A said:
On the other side of the wall there's an airing cupboard and the wall isn't damp but the paint is all flaking off.

Just been on the phone to my dad and he said it could be 'efflorescence' which seems to fit the salt on the walls etc.

Above that wall is nothing, it stops in the loft and supports the timber ceiling joists. So I cant work out where the water is coming from. Unless its coming from next doors.

Would knocking the plaster off and tanking it sort it do you think?

The only other thing I can do is have a look at the chimney stack to see if the flashings are damaged. But surely if that was the case the chimney stack in the loft above the damp area would be damp?
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efflorescence is the salt on the walls

tanking is an extreme resort for what could be a simple problem such as condensation causing the damp, have a look in the loft above the damp patch and see if there's any visible signs where water has collected and ran or followed a path to the damp area below

speak with your neighbour and ask if he has any problems


edit: have you checked the state of your chimney?
 
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Tanking won't work, it will simply move the problem else where, moisture always finds the easiest path, if you block one it will appear elsewhere.

Can you draw us a plan of the area and surrounding rooms?
 
Hmmmmmmm. I have seen this before.

Most likely causes:

1) Broken render/guttering/tile/pipe etc leaking into or onto the affected area.

2) The salts in the bricks and mortar are being pulled through by the plaster. Has the plaster in that area been touched up at all? I had some plastering done in the living room years ago where some inside render came away during electrical building works. The plasterer applied normal gypsum plaster straight to the wall. It never dried out fully, and is still producting salts 3 years later. The remedy is to hack off the plaster and render with 3:1 sand/cement and a waterproofing/salt inhibiting solution. THEN plaster over the top of that.
Hack off the affected area and see if the wall behind is relatively dry (compared to how wet the plaster feels) - if theory 2) is correct, it probably will be. Once the plaster is hacked off the area should dry out.

See some more bits of info here:

http://dampdecay.co.uk/index.php/your-questions-answered/60-damp-plaster
 
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Here's a close-up pic of the salt like substance I was talking about.

The plaster has been touched up in places. There are bands of pink plaster going horizontally around the room, the rest is the old white plaster. I don't have a clue why there are bands of new plaster as usually cables go either down or up, but the council did the work so it could be anything.

I'll knock a bit off tomorrow and see what the brickwork is like. like I say though, above that wall is nothing, its an internal wall so its nothing to do with the gutters or anything. It can only be the chimney stack or maybe next doors walls are damp and its being pulled through in that area due to the salt in the plaster?
 
Unusual to see it on an internal wall, is the wall attached to an external wall? The damps and salts will travel right through the plaster.

I'm not saying I'm right, it just looks ever so familiar!
 
The wall is attached to next doors wall (semi-detached) and that wall goes right up to the roof. That's also the wall that the chimney stack is on.

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Also slightly damp on the top of the chimney stack. But in the loft I cant see any sign of damp.

Its strange how the damp patch just stops suddenly and also that the paper wasn't damp.
 
Check the chimney pot , check chimney flashing and the condition of the roof, speak to your neighbour, buy a damp meter and check from the loft and down, you can't always see where the moisture is, look for discolouration of wood in the loft, darker areas can be signs of it being wet at some point
 
The timber all looks pretty sound. I think the ceiling has been redone at some point as its that plaster with the silver backing.

The wall and chimney stack feel dry but as someone said it could feel dry but not be.

What could those bands of new plaster be do you think? Seems strange they have put new plaster in channels around the room like that. The damp appears to be travelling along one of the new plaster channels away from the main damp patch. I'm tempted to knock some plaster off tomorrow and make sure there isn't a pipe behind there :eek:.
 
It's probably a cable or a pipe of some kind. Get a detector for pipes/cables first. Last thing you want to do is crack a gas or water pipe! Get a damp meter for plaster too as someone has already recommended. They're cheap off Ebay and very useful. I'd recommend the type with the needle indicator or a digital one over the ones with 5 lights on them.
 
Have you checked for pipes around that area in the loft or used a pipe detector over the new plaster in the wall?

Could be a fixed leak thats still drying out.
 
Lostkat said:
It's probably a cable or a pipe of some kind. Get a detector for pipes/cables first. Last thing you want to do is crack a gas or water pipe! Get a damp meter for plaster too as someone has already recommended. They're cheap off Ebay and very useful. I'd recommend the type with the needle indicator or a digital one over the ones with 5 lights on them.
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Thanks for the advice, I'll get a damp meter as it'll also come in for testing the water content of wood.

http://cgi.ebay.co.uk/Rapitest-Elec...568?pt=LH_DefaultDomain_3&hash=item1c15355f10

Something like that? There are some for like £5 from HK but I'm not sure they would be very accurate.

Just knocked some plaster off down to the brick and it looks dry. I'm beginning to think that it's just the plaster with some sort of coating that's making it look damp.
 
Mark A said:
Thanks for the advice, I'll get a damp meter as it'll also come in for testing the water content of wood.

http://cgi.ebay.co.uk/Rapitest-Elec...568?pt=LH_DefaultDomain_3&hash=item1c15355f10

Something like that? There are some for like £5 from HK but I'm not sure they would be very accurate.

Just knocked some plaster off down to the brick and it looks dry. I'm beginning to think that it's just the plaster with some sort of coating that's making it look damp.
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icon14.gif
Same one we have
 
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