Damp on chimney breast - specialist to use?

Hi, my neigbour's chimney has started to show a damp patch coming through our bedroom wall. Since weve just decorated with expensive wallpaper were a bit annoyed by this. They have had a wood burner installed in the last 6 months (no liner) and I'm concerned that this may be the cause of the problem. Who would be the best specialist to advise what the problem is so I can go armed with the facts as to whether its the wood burner, or just damp from a leaky tile etc. How much can I expect to pay for such a service?
Many Thanks.
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Dear Richard There are two possible issues. Are the stains the result of the recent change to a wood burner? or Are the stains the result of fossil fuels over the last century or so - a common cause of hygroscopic salts (usually a light brown or yellow stain)?
For the former I suggest you look at building regs and see if the wood burner has had a proper flue installed and, if so, it can be eliminated
If not then an expert in installing such wood burners and the effects of not doing it properly is the person to call in
If it is fossil fuel burning then you need no expert. Just remove and render the affected plaster or if that does not appeal "botch" it by covering with a specialist stain plaster
Do check that there are no indications of water penetration from outside
Chris
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Many thanks for the reply, answers inline...

New burner was installed 6 months ago

quite possibly, I need to determine which therefore.

No flue installed (I asked at the time because I was concerned). Also it seems like the capping hasnt been replaced - there seems to be only a small gap between the slab and the chimney top for smoke to escape (about 3 in I estimate). When I installed my burner, I changed the slab to a chimney pot, hence my concern!

Will they be able to definitively tell me if its damp or tar? Can damp also be caused by condensation of the combustion vapour the top of the flue as I dont see the stain further down the wall, or downstairs?

It could be fossil fuel since thats what a house built in 1863 would have used for years, although none of my other walls over chimney breasts have such stains despite being used for fires/wood burners. We had upstairs decorated recently, but I dont recall any stains on the old (albeit thick woodchip) paper. Furthermore, our new, now stained, paper is one of those embossed Laura Ashley types, and I can see the stain/damp coming through it even though it is probably more resistant than the lining paper used everywhere else (including over the other chimney breasts).

Will do - are the damp meters any good for detecting such penetration?
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If it is a wood burner and improperly vented it is probably a fire hazard as well as a source of tar discolouration. If it is damp a small gadget will tell you. If it is tar it will be yellow and stain through all known wall coverings.
No paint made will stem it. Maybe some Visqueen under aluminium faced plaster-board might. For a while.
You are wasting your time getting in an expert. An house surveyor will charge hundreds and may exclude the terminology you'd need to win a law suit. They have seen the light about public liability.
If you can convince your neighbour he is a fool, he might stop acting foolishly but how likely is that? The tar will eventually spread around the entire building. It is as insidious as mould.
Get a ladder and check the chimney tops. If they are open and you don't have fires below them, you need to cover the vents and leave a small air gap. And you need to cover the fireplace and vent that too.
Also check for damage to the sides of the chimney. Missing lead flashings for instance. A lot of scrap metal crime is going on at the moment. Maybe you have been a victim.
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Many thanks, please see inline...

I'll try and get the gadget from screwfix to determine if damp or stain from tar - but is it not possible that it would be damp and tar - both from the fire due to improper venting (see my other reply re condensation as their fire is not used that regularly as far as I can tell).

Even if I convince him to stop using the fire, the next person may not be so obliging, so I need to stop it now and before we redecorate (again!).

There is a ground floor and first floor flue feeding the chimney (both on his side). The downstairs one is fitted with wood burner (no liner) and the upper is sealed I believe (probably vented if my fireplaces are anything to go by). Chimneytops no longer have pots on this stack, and have a slab over both flue exists with what I consider to be a small (3-4 inch) gap.

Will do - thanks.
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I've just got the recommended gadget and it is clearly damp coming through the wall/chimney. 0-5% moisture on unaffected patches and 30-35% as soon as get to the "stain" part of the wall paper. Whether there is tar/something else also coming through at the same time I dont know. I've been into the loft to check for water ingress. Put my hand on the chimney breast bricks directly above the stain in the bedroom and cannot seem to find any obviuos indications of water coming in. Besides which the stain is in a the shape of flue - i.e. it snakes up at an angle rathen straight down - it also gets wider at the top and narrower at the bottom - both of which I would suggest are issues with the wood burner. On the other hand, if they dont use it for a while, surely the stain will dry out?? That would confirm whether it is the burner or not - or am I missing something?
Anyway any advice gratefully received as per usual!
Richard.
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Richard wrote:

1. damp meters measure resistance, not damp. Soot conducts too. 2. the solution was explained last month. 3. If you want a guarantee you'll need to employ a building firm willing to give a written g'tee. for which you'll pay silly money. Your choice.
NT
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Richard wrote:

Try putting a layer of kitchen towel at the base of the chimney breast in the loft. Even if it dries out you'll be able to see where it has been wet. Condensation from the breast I'd say
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Richard What evidence have you that damp is coming THROUGH the chimney? In what way does a reading on the surface with a resistance meter indicate this rather than hygrosopicity which comes and goes WITHIN THE PLASTER with the RH and which was presented to you as an alternative explanation when I said "or Are the stains the result of fossil fuels over the last century or so - a common cause of hygroscopic salts (usually a light brown or yellow stain)? " I have been surveying such properties for well over 30 years and in the vast majority of cases it is not external water penetraton from a cover flashing or the like but hygroscopic salts contaminating the plaster, chris PS btw the 'percentages' are not percentages of moisture content but an indicator of relative resistance
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Good advice from Weatherlawyer. It sounds as if you need a good local builder to take a look at it but I can't tell you how to find one. One thing. Have you had your chimney breast removed? if not then I would expect the stains to be a lot worse on his side.
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Thanks for replying. Chimney breast doesnt exist my side and never did - were in a terrace and hes the end one so theres no back to back arrangement on that side - it is back to back on my other wall however, with no such issues.
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Richard wrote:

Probably either hygroscopic salts or fumes leaking through cracks in the chimney to meet the back of the paper. Either way, removing the patch of plaster back to the brick and replastering it would do it.
Beware of damp 'experts', most are better avoided.
NT
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On 25 Feb, 15:21, snipped-for-privacy@care2.com wrote:

Thanks. True, that may work but I want to be certain it doesnt happen again before I redecorate (even if he pays - I'm fed up of the DIY disruption!). If its leaking fumes, then making him install a liner seems the way to go - but can I make him do that legally, if he doesnt want to play ball?
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