Ummm ... just removed some wallpaper and ...

... a bit of the wall wanted to come with it! Was using a steamer at the time and the plaster behind the paper bubbled right out. Held it against the wall until it cooled down and dried a bit. Now it's completely dry, it's still in one piece, but cracked a bit and definitely not sound (it pushes back a couple of mm).

What are my options now? Can you knock sections out and put a "chunk" of plaster back in? Should I ignore it, fill the fine cracks with Pollyfilla and paper over it? I'm not sure what's behind it - would it be the skimmed plaster and plasterboard be behind or could it just be thin plasterboard? It's a 1930's house if that's relevant.

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Reply to
al
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After reading a little further, I believe the second option I was referring to is called dry lining. Would this have been done 70 years ago?

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Reply to
al

Knock out the blown plaster ( carefully ) and go and buy some plaster, or maybe polyfilla will do if they say it's alright for the thickness involved, and patch it. It's not possible to 'feather' in plaster invisibly, so there'll be a slight line where the new meets old, but nothing that'll notice behind wall paper. Polyfilla is much better for feathering in.

Patching a small area of plaster is not that difficult unless you're all thumbs. As for plasterboard in a 70 year old house, I'm not sure, but I'd lean towards lathe and plaster rather than plasterboard.

Reply to
andrewpreece

There's no need to feather - the patch wants to be flush with the original plaster. This is flat walls we're talking about, not dents in cars.

Reply to
Rob Morley

Unless the house has been modified in recent decades you won't have plasterboard - it will be plaster on masonry or on wood lath. You might find it's just the surface of the plaster that's loose. If so you can just remove any loose bits and make good with filler or finishing plaster. If the full thickness of plaster is coming away from the wall you could remove the loose bits and fill the holes with one-coat plaster, but you might find that once you've removed all the loose bits there's not much left. Or you could patch the cracks with filler*, cover it up and hope it stays there until the next time you decide to decorate.

  • Scrape the cracks out with a putty knife or similar so you can actually get the filler in, rather than just smearing it over the top.
Reply to
Rob Morley

Do you think there is plasterboard behind because it all sounds hollow? If so its because the plaster has detatched itself from the bricks. Its probably bowed out in the middle and will eventulay all fall off anyway. In your situation I replastered about 2/3 of the house but I wasnt living there. You could maybe do the one room but its going to be messy. If you do just patches I believe people inject PVA glue into the gap behind to try to hold the old plaster in place. If the gap is over 1/2 inch then that would be pointless I think.

BTW some 1930's houses did have plasterboard ceilings and stud partitions but this is not related to your problem. Dry lining is a modern thing not 1930's.

Basil

Reply to
basil

We had exactly the same thing happen when we were stripping our walls. We found that it was generally just the final skim layer that popped off, the bulk plaster behind it was fairly sound.

In one room the bulk plaster was very dry and sandy so I stabilized it with PVA before putting a skim of plaster over it.

If the bit that's fallen off is fairly small (few square feet) I suggest you skim it and leave just a tiny bit extra plaster / filler where old meets new and then gently sand that back. I have done this is a couple of places and you can't see the join. If more has fallen off then either practice plastering or get a plaster in. I have become quite good at plastering now :-)

Before you steam the walls just go round the room and tap the walls with your fingers. If anywhere sounds hollow you can be pretty certain that it will fall off when you steam it as it has already partially come away anyway. We found that just doing those bit by hand saved quite a bit of re-plastering.

Graham

al wrote:

Reply to
doozer

It's about a 10cm circular area, so not too big. Should I just try gently knocking it out with a chisel then and using Pollyfilla to build up the missing plaster? It seems like a thin layer from the flexibility of it - I would guess about 5mm or so thick. Sounds like this would be the final skim layer from your and others descriptions.

There's a few places like that all right ... looks like I'll have fun!

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Reply to
al

I found that if the bubble looked like it was about 10cm when I had taken off all the loose plaster the hole had normally grown to about

30cm (in one case it was much bigger than that though). Even so that's still pretty easy to fill yourself with a little patience.

You shouldn't need a chisel as it will come away easily and in the interests of doing as little unnecessary work as possible you don't want to damage the underlying plaster as that is probably good enough to work with. I used a old wall paper stripper - dig the edge into the bubble and gently lift away then scrape off the rest of the loose skim like you a lifting wall paper. Be careful you don't get carried away and scrape the whole wall off! The material should come away really easily and is probably currently being held together by a layer of paint at a guess. If the base plaster is very sandy and dry you might want to paint it with PVA first.

The final skim thickness will vary from place to place around the house. Some places it will be as little as 1mm others around 5 or 6mm. I found the thicker bits easier to fix. Just mix up some nice smooth filler and slap it in the hole. Smooth it with a filling knife (or float if the hole is big enough to warrant it) leaving just a little extra at the edges.

Leave it to dry thoroughly and then sand the edges (120 grit should do it) smooth with the original wall, if you need to sand the middle bulk section do that as well. Run the palm of your hand over the filled section to check for bumps and steps between old and new. You shouldn't be able to feel a ridge. If you do feel a ridge try and guess whether your new filler is to high (in which case sand a little more) or to low (in which case fill a little more and repeat sanding). You can get a finish that is easily good enough to paint.

Graham

Reply to
doozer

The filler to use - anything in particular? I have a fresh tub of standard indoor Pollyfilla which is light and creamy. Should I try and fill the entire depth at once or build it up?

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Reply to
al

If you've got more than a couple of millimetres thickness to fill I'd use one-coat plaster. I use the stuff in white plastic sacks with red logo & printing on it, from B&Q (and maybe other places - it's not an own-brand but I can't remember the brand name). That goes on up to 50mm thick (they say) and doesn't sag the way polyfilla does. There are own-brands in the sheds which may be alright - I haven't tried.

Actually I don't use polyfilla for thin bits either - I tend to use Tetrion or even cove advesive (shed own-brand is quite cheap) which I'm sure is the same as cellulose filler but vastly cheaper. There's also a white cellulose filler in paper sacks, about £10 for 10Kg, which is very good for fine filling. You'll find it (and one-coat) by the bags of plaster etc in the trade section of big B&Qs.

Before filling I'd prime the area thoroughly with PVA, diluted enough to soak into the plaster rather than dragging loose stuff off into a sticky mass/mess. If you've had to dilute the PVA much to wet the wall you can give it another dose of less-dilute stuff (DIY law#94: you can never have too much PVA :-). You can apply filler before the PVA has dried or afterwards, doesn't seem to matter either way (though I daresay some smartypants materials scientist will be along to correct me on that ;-)

Reply to
John Stumbles

I agree. I thought from what you described originally you only lost the surface skim. If you have to fill deeper than a few mills one coat filler is the ticket (it's much cheaper than polyfilla). If it is just the skim then polyfilla will work. I tend to use B&Q own brand filler as it's cheaper and does the same job (got the bargain of the century on it, 30p per 1.5kg bag because of a stock take).

Reply to
doozer

I've pried away some of the shot plaster and it's about 3-4mm thick, so not nearly as bad as I thought. Haven't got any PVA ... will see how much of the wall I destroy by the time all of the paper is down first - don't know if it comes in small amounts.

Managed to steam burn my wrist so far, which is a great help!! Lessons to be learned about being careless with paper steamers!

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Reply to
al

Haven't got any PVA?

HAVEN'T GOT ANY PVA?!!!

And you have the temerity to show yourself on a DIY forum?!!!

;-)

Reply to
John Stumbles

Sorry, neither have I - what do I need that for?

Is it any good for a loose mortice joint in a sofa?

Reply to
Sue

Ummm .. no ... and .. ummm ... yes! ;p

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Reply to
al

Speaking of PVA ... I'm looking to paint my garage walls & floor soon. Would a standard PVA solution do me in this circumstance as a primer to floor/wall paint also? Floor is porous concrete and walls are mostly (very) porous brick and one pebbledash.

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Reply to
al

I painted our garage floor last year, it too was porous concrete, I just used floor paint straight on to the floor and it worked fine (cheapest bit of DIY I've ever done - the previous owners left the paint behind). Don't forget to stir the tin before starting though (I did and had to redo a good portion) being oil based it had separated but it didn't look like it had from the top.

Graham.

PS. Has anyone else had PVA go mouldy? I found half a tub that I had forgotten about, when I opened it up it had a sort of mould growing on top of it. I would never have thought that something could live off PVA.

Reply to
doozer

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