Wall disaster in living room

Due to some water hitting the outside wall from the guttering last year, it has caused the wall paper above the windows inside. And the plaster below the wallpaper is very sandy and crumbly.
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Could someone advise a complete novice on the best course of action please. My immediate reaction is to go to somewhere like B & Q and get some repair plaster. However the existing plaster is so very sandy and crumbly and so I'm not sure whether to knock it all off, or whether i can paint it with something that would 'solidify' it? (I've never done any plastering before but have heard that it's not that easy).
Then I thought I would put some Polycell surface filler down before putting emuslsion paint on top of that.
Grateful for any advice simply explained for a novice about the best way to deal with this problem please. Thanks.
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On 02/12/2010 15:22, john leigh wrote:

You could try knocking off the worst of it and skimming with filler, which is more likely to bond to a bad surface than plaster, and is much easier to use. If you leave what looks like a right angled corner intact, a plasterer's trowel will have something to follow. Easier to do than explain how :-)
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Stuart thanks. Is there any particular filler you would recommend? The bit of plaster I did knock off fell off right up to the brick work, so i'm guessing I might need quite a bit? Thanks.
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I'd soak it in dilute pva (something like 1 part pva, 5 parts water) - that'll stop the dusty/sandy crap. Then a proper filler - I like the polyfilla trade stuff from screwfix personally
http://www.screwfix.com/prods/36426/Sealants-Adhesives/Fillers/Multi-purpose-Fillers/Polycell-Polyfilla-Trade-Interior-Filler-2kg
but most will do. That'll get pricey if the area is large - you might want to look at one of the onecoat plasters (onecoat can go on thicker). You can probably even get premixed vats of the stuff from wickes etc.
I've had excellent results skimming stuff with Gyproc Easi-fill. If you aren't any good at plastering then it's much easier to use - not sure what the max thickness is though (if it's good enough for you, I'd recommend it).
http://www.british-gypsum.com/products/plasterboard___accessories/gyproc_accessories/gyproc_easi-fill.aspx
Excellent stuff - and sandable if you do balls it up unlike proper plaster :)
Darren
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On 02/12/2010 16:27, john leigh wrote:

Any old interior filler will do but, if you're back to the brickwork, you should be looking at a bonding or multi purpose plaster, or it will cost a fortune.
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On 02/12/10 15:22, john leigh wrote:

Saturating it in 1:4 SBR:water will solidify it enormously. SBR has better penetrating powers compared to PVA.
--
Tim Watts

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It is possible to glue plaster together, but its only worth doing if it avoids striping and replastering. Once its deformed like that I'd knock it off.
NT
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wrote:

It is possible to glue plaster together, but its only worth doing if it avoids striping and replastering. Once its deformed like that I'd knock it off.
NT
Glue plaster together? I think they do that in the cartoons. LOL
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wrote:

Watch cartoons do you? Beep beep prat.

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wrote:

In days of yore plaster was not as it is today. The "crumbly" appearance may well be OK. So long as it is still stuck to the wall. If it sounds hollow when you tap it, it will have to come off. It has "blown". Probably a lot more than you expect will fall away too. You may end up doing the entire wall. The wall can then be cement rendered and finished with plaster. If it is not hollow, you can soak it with PVA "bonding agent" (there is a special grade for this) several coats starting diluted and later ones less diluted. It can then be refinished. I f you've never applies plaster it's best to get some "Polyfilla" or similar. Doesn't go off as quick, much easier to deal with.
What about using plasterboard - dab and dobbed onto the brickwork?
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John wrote:

+1
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crumbling lime plaster isnt much good. It needs to be glued or lime watered as a minimum, otherwise it keeps crumbling off.

This is often said, but not true. If its hollow and thin or breaking up, then it'll break up readily and needs removing, but thick firm hollow sounding plaster in good condition is fine.

sometimes yes, sometimes its just a patch that isnt bonded to the wall under it, and if the stuff's good & firm & not moving that's not a problem.

don't cement render historic brickwork

any grade will work. I'd only give it one go, once its set it doesnt allow more to soak through so easily. Brush on, let soak in for 10 mins, brush more on, etc, but dont bother coming back another day to repeat.
NT
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