Damp help

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Ok. So hacked off about 8 inch from.the floor up the wall. And it seemed to disappear. Now...its rained last two days and it's. Back.

This is an internal wall. Joining the neighbours house. She has no damp. It's only on the bottom half of the wall. Any help?
 
Mike, the damp looks like the masonry & multi was never completely dry before painting. If the chimney and flue is the culprit, there normally be signs on any upper floors also. Rainwater pipe not throwing water away from the building or water generally running back towards the house during heavy rainfall. Can be difficult to spot & wont necessarily cause your neighbour any problems.
Had exactly the same problem on an internal wall in a converted stone steading, plastered on the hard as they wanted to keep the curved wall. Never found the exact source of water so used hacked off, Newton membrane & plastered. (Used damp comp for guarantee)2 years and still dry. Chemical is far too hit & miss. Hope this helps
 
Jumping into the thread very late but I'd seriously consider getting a proper plasterer in (as you did say you aren't one?) because they'll spot stuff you might not.

They'd also sweep your floors and plaster off the floor lol
 
Are you sure you have not got a ground water issue or a drainage problem ?

I have looked under floors and seen a small spring running under a couple, all about building years ago without knowledge of ground water issues.
 
Hi you need to find out if its a rising damp problem or salt contamination from hygroscopic salts, I messed up a few jobs because of this and it cost me lots of dollar! This is how I met the bloke that taught me about this, he went against me and proved that there was no leak and it was my fault. I've also been caught out with salt contamination when I re-plastered a barn with lime mortar, lime mortar will not stop salts from an old rising damp problem or cattle pee. Before you waste any more time or money have a look at this link, this bloke knows his stuff and has a lab for testing samples of plaster and moisture profiles, you could speak to him and send them to him.
The damp stains on the chimney breast, is it salt damp or a leak? | Welcome to Complete Preservations blog
 
Anti sulphate will not stop hygroscopic salts from long term burning of fossil fuels or from rising damp, these salts are soluble nitrates chlorides not sulphates.
You can see from your pic that you have gypsum touching the red brick on the chimney, this could be tracking salts across the wall, or it could be that your scratch coat was not of a 3-1 grade m sharp sand with an adequate salt resistant re-plastering system. There are so many variables, people can only guide you as they weren't there when the work was carried out.......Many people claim to know about damp proofing and damp meters and don't understand how they work or should be used. Bre Digest 245 is how it should be done, you need to profile the wall and take samples, this will then give you quantative results. Most people stick a £10 meter in a wall and it goes red and you have rising damp, lovely another chemical dpc to install, in reality it was problem a condensation problem.
Hers is a link to profiling the wall
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Skimmy1 said:
Anti sulphate will not stop hygroscopic salts from long term burning of fossil fuels or from rising damp, these salts are soluble nitrates chlorides not sulphates.
You can see from your pic that you have gypsum touching the red brick on the chimney, this could be tracking salts across the wall, or it could be that your scratch coat was not of a 3-1 grade m sharp sand with an adequate salt resistant re-plastering system. There are so many variables, people can only guide you as they weren't there when the work was carried out.......Many people claim to know about damp proofing and damp meters and don't understand how they work or should be used. Bre Digest 245 is how it should be done, you need to profile the wall and take samples, this will then give you quantative results. Most people stick a £10 meter in a wall and it goes red and you have rising damp, lovely another chemical dpc to install, in reality it was problem a condensation problem.
Hers is a link to profiling the wall
Link Removed
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Nice posts skimmy1, do you reckon the salts would have been visible on the original surface prior to the gypsum skim?
 
@perlite

Mike Adams wrote "The walls in question where stripped of all wallpaper and pva'd then skimmed"

If the wall paper was wetted or steamed to be removed this can mobilise salts in the wall, same as when using lime mortar, you wet the walls down which can then bring salts to the surface as they evaporate. Pva re-emulsifies when wet 2....... Were the salts visible? Maybe maybe not, this is where a damp meter can be of use and a humidifier as this will show hygroscopic salts absorbing moisture from the air. Sometimes they are not always visible if the relative humidity is low, they also appear just before rain when the relative humidity rises thats people think that the damp patch on the chimney is from a leak
Anybody working around a chimney needs to think about salt contamination issues, party walls normally have the highest height of rise when it comes to rising damp as they are rendered both sides which doesn't help when it comes to evaporation.
 
I've had problems with lithomex nhl mortar I'd put down to laitence where it had been finished with a trowel. salts are even trickier to pinpoint than a source of water. A lot of the stone repairs we do were originally caused by salt migration to the face, but are not a problem when the lime mortar is left open. How are you treating internal salts now .brushing?
 
I've an external rendered & painted wall blowing off the paint every summer to sort out & I reckon it's a contaminated wall. I'm hoping to avoid removing all the render if possible
 
carlos said:
Thats is a new one to me. Do you not mean spraying the brickwork with it?
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We do a lot of work on stone houses and we sometimes drill the beds and pump in a bit of anti sulphate with a sprayer if its particularly bad, top surface sometimes ain't enough, I wish I did more brick houses lol, one scratch and a tight float, the stone houses take 4 or 5 coats before skimming :(
 
Av never heard of that before, we just coat the surface with 2 neat coats of anti sulphate. It's an interesting thought though. Is it effective?
 
Well we do it mainly due to all thickness, stone can be 850 mm + in thickness at times so we thought that top surface really isn't enough.

It seems to knock it back well, we like to try to saturate it as much as we can.

I guess cavity brick would be ok with top surface but solid wall might benefit from injecting, just drill out the perps at an angle ?
 
So I hacked of the plaster on the walls.
I had a good look at the old bitumen style dpc and noticed it was a bit rotten in places. So gave it a new dpc with the injection creams you can buy. Now waiting for that to all dry iut I'm still yet to find the source of my problem. But once I do and have to re plaster what do you suggest? Dab? Sand cement? Tank?

It's bare brick. Internal walls.
 
Tank the brickwork if you want to be OTT but me personally if its an internal I would use renovating plaster or an insulated board.

I tend to mainly worry more about external walls, cold surfaces etc.
 
My prof said he is leaning against tanking in favour of always having walls breath, insulated damp proof board with some breathable insulation and let those bricks dry off.
 
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