Plasterboard on corner of brick wall

17 Dec 2014
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United Kingdom
I've had to remove the plaster on the side of our chimney breast. I'm going to batten it and reboard the side but i'm not sure what to do with the bits on the front of the fireplace.

As you can see from the picture I've had to hack off some of the loose plaster, when it gets skimmed next week could the plasterer simply fill it in? Or should i square it off and dab some 12mm plasterboard to wall?
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Personally would dot n dab boards rather than batten out.
The corner section can the be repaired with bonding coat, leave about 3mm off of level/flush, then apply a thin coat bead and plaster with multi-finish.
Hello rhodes73,

that looks like an easy repair job but I am wondering what the reason is that this section has had to be removed? . . Is there an underlying issue that needs to be dealt with to avoid the same thing eventually happening again to the new patched area?

I was reading that hygroscopic ammonium, chloride, and nitrates salts from the burnt fossil fuels build up in the bricks inside the fireplace and cause problems like plaster deteriorating and falling from the underlying brickwork.

I believe there is some kind of wash that you can use on the exposed brickwork to stabilize them so that the bad stuff in the brick doesn't seep out again.

Apart from that I would just use bonding undercoat plaster to fill out the old brickwork and finish with a little skim.
as wayne says, were there signs of damp on that wall at all.
If not then I would use a thick coat corner bead, dub both walls out with bonding or hardwall and then skim. Your plasterer can take care of all of that
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Tap the existing plaster and see if its "Boxy"...
Tap the existing plaster and see if its "Boxy"...
That old chestnut started doing that after taking a door lining out on Wednesday two walls, now need completely floating and setting. Not convinced the other two are any better in reality but it stopped falling off so I stopped too.
we still dont know why the plaster was removed or if any damp is present - although the wood packings look to be sound.
Sweeping the flue(s) would eliminate some of the soot penetration risks.
A pic of the front of the c/breast would help?

You could "square off" to a plumbline, & render with sand and lime or cement as a just in case measure.
There's a gas fitting in the pic - is it live?
The wood corner packings need removing.

FWIW: Corner beads are known to me as: "angle bead" for floating, and "skim bead" for finish. I've never heard or used the terms thick or thin for corner bead.

There's no such "wash" to stabilize" against hygroscopic salt penetrations.
Thanks for the suggestion but sure, they sell snake oil as well - the thing is does it work?
In my experience these concoctions dont work - the salts continue right through them to the finished surface.
The Remedial world is full of wonderful chemicals and devices but sad to say almost none of them work as claimed.
I would say they do, do what they say on the tin but the effect can be temporary. I have used similar products on efflorescence on bricks and it generally does work but it can be temporary. They are neutralizers not sealers, when you apply some it soaks in and reacts with the salt in solution, that might be it. But if you have a lot of moisture say totally soaked bricks then as the remaining moisture continues to drive salts out as it dries then the treatment can become ineffective again.
Bottom line I would say is their longterm effectiveness is patchy at best.
A waste of time and money using such nonsense below a remedial covering such as sand and lime.
Never use any of these concoctions in a remedial situation.
I'm not sure if we can write off treatments like anti-sulphate as nonsense snake-oil, there is some science to it which makes sense but it's hard to tell from the O.Ps photo what the exact problem is that has caused the surface plaster/render to debond. If it's an ongoing damp issue then I agree a wash isn't going to help much but if it's an old damp issue that has been fixed and/and or a problem caused by nitrates from the original fire place seeping into and contaminating the brickwork of the chimney breast then a wash that "makes soluble salts insoluble and prevents further movement" seems worth a punt to keep you out of trouble.

Looking at the O/P's photo its look like render not plaster that's been hacked off? . . . Also there is a small hole in the ceiling. Who knows this may actually be a previous damp repair that wasn't done very well but personally I wouldn't go to the bother of making good without trying to figure out what has cause the problem.
Dont mix up my generalised final point about concoctions & remedial work, and the particular case in the OP's pic.
"ongoing damp issue" or "old damp issue" there's no such solution for salts - you could wash the salts off with tap water and it would work for a while but it would not be a solution.

As for hygroscopic chemicals that penetrate a chimney breast, and appear on the decorated surface - tell me, how would you treat them - with your neutralisers?

And staying on page - how would you use the neutraliser where low level "rising damp" salts show on wallpaper?
What is all the speculative excitement about a previous leak about?
There is no evidence that there has been a leak, and the hole in the ceiling is directly above a gas fitting.

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