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PostPosted: Mon Sep 22, 2008 2:43 pm 
Old School Grand Master
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Location: Penarth
Could anyone help with a wee problem.
I'm decorating my kids bedroom...and one patch keeps bubbling up. :x
The building is stone built. The walls are plastered...bit of a mix of old and new as you can imagine with a 100+yo property.
We had experienced some damp/mould growth on exterior walls so I have applied one coat of fungi-shield followed by two coats of undercoat (watered white emulsion) followed by two coats of emulsion top coat.
This is the same for all the wall...but on one bit there is some sort of reaction causing the paint to bubble and raise.
Any suggestions?
Cheers
Carl


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PostPosted: Mon Sep 22, 2008 5:27 pm 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
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Location: New Forest, UK
If it's downstairs, it maybe a salt buildup in the plaster - the only real remedy is new plaster.

As a first try, I'd try a PVA / Water mix (about 1:5) which usually does the trick for me.


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PostPosted: Mon Sep 22, 2008 6:26 pm 
Lincs AEC
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Sounds like it needs tanking. A cottage I used to own had the same problem, had it tanked and replastered, voila, problem solved.


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PostPosted: Mon Sep 22, 2008 6:42 pm 
Old School Grand Master
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Thanks fellas...it's only one small patch...no bigger than an A4 sheet of paper. Probably try some PVA to see if that seals it, but I would have thought the Fungi-shield would have done that job :?
Flipping annoying after all the prep :evil:


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PostPosted: Mon Sep 22, 2008 7:23 pm 
MacRetro rider
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You could scrape/cut out the offending area (+ a sensible border) glue/screw in a piece of foil backed plasterboard (make sure it is recessed) and skim it level with the wall again.

But best solution is to take down the whole wall back to the brick (I'm guessing it is an exterior or chimney wall) tank it if necessary, then put up studding and plasterboard and have it skimmed.

I did this to my sons room last year, you can do it all yourself, but I got in a plasterer for the skim coat.

Better than leaving a damp area to fester, especially a room you sleep in.

.....also check the outside wall for any old metal work near the area, that can draw in the damp - either remove it or refit it with new wall plugs.


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PostPosted: Mon Sep 22, 2008 9:57 pm 
Gold Trader
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i work as a craft mason so old buildings are my speciality, if i were you i would try an alkaline sealer, you wont find this in homebase or b and q , you will have to go to a dulux trade centre or similar trade shop
, it is most probobly due to effloresence ( a build up of soluble salts ).

just a quick note. if your building is solid stone, then despite what many people might tell you it is unadvisable to tank the wall. beleve me i know what i am talking about, i have to remove tanking a lot to sort out damp problems !
ideally in a perfect world it should be rendered or pointed with a lime mortar on the exterior, and depending upon the finish inside it should also be rendered smooth with lime , and then skimmed with a lime putty ( this when applied properly can produce a marble like finish !! ) . im sure you have heard people talking about letting the walls breath, it is important if you dont have a cavity construction.
allthough im ranting on and realise you are just trying to paint a room , i thought id let you know because tanking can be a very expensive mistake ( yes a lot of the time it is okay , but problems generally get pushed in to other parts of the building). i get a lot of work sorting out damp problems in old buildings.
and for the right job i will travel anywhere in the world to practise my craft :wink: :lol:
cheers


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PostPosted: Mon Sep 22, 2008 10:20 pm 
Old School Grand Master
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Thanks again peeps, particularly Mr Tea for a most concise post.
The exterior of the building has been re-pointed front and rear, but the sides have been 'rendered' with that rough stuff :? ..can't explain it.
The 'developers' who tarted it up fitted double glazing...that doesn't appear to have vents. They also papered with thick woodchip and painted over that again. I suspect they also papered over not-fully-dry plaster in places. I think the combination of all the above has resulted in the black mould (not very bad, just not good). Basically, as you say, I think the walls have been unable to breath.
I shall get some alkaline sealant stuff and see what happens.
Thanks again
Much appreciated.
Carl
Can't tell you how much I like stripping that woodchip off :lol:
PPS I would love to have the walls properly plastered....that marble finish with the lime putty sounds gorgeous....but I'm skint. I'll give you a shout when the boat comes in :wink: :lol:


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PostPosted: Tue Sep 23, 2008 1:03 pm 
Old School Grand Master

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Location: New Forest, UK
There's great stuff called Zinser which covers almost everything, but it's horribly expensive.


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PostPosted: Tue Sep 23, 2008 2:17 pm 
Old School Grand Master
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magicmistertea wrote:
i work as a craft mason so old buildings are my speciality, if i were you i would try an alkaline sealer, you wont find this in homebase or b and q , you will have to go to a dulux trade centre or similar trade shop
, it is most probobly due to effloresence ( a build up of soluble salts ).

just a quick note. if your building is solid stone, then despite what many people might tell you it is unadvisable to tank the wall. beleve me i know what i am talking about, i have to remove tanking a lot to sort out damp problems !
ideally in a perfect world it should be rendered or pointed with a lime mortar on the exterior, and depending upon the finish inside it should also be rendered smooth with lime , and then skimmed with a lime putty ( this when applied properly can produce a marble like finish !! ) . im sure you have heard people talking about letting the walls breath, it is important if you dont have a cavity construction.
allthough im ranting on and realise you are just trying to paint a room , i thought id let you know because tanking can be a very expensive mistake ( yes a lot of the time it is okay , but problems generally get pushed in to other parts of the building). i get a lot of work sorting out damp problems in old buildings.
and for the right job i will travel anywhere in the world to practise my craft :wink: :lol:
cheers


/\ What he said. /\

I concur, the worst thing for solid stone (or brick) walls is cement based renders and mortar along with modern paints. Most damp problems are due to the wall not being able to breath.
Lime mortars and renders are ideal along with distemper and lime wash colours.
Clay plaster works too and looks very cool.


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