Dodgy plaster and cornices

Running your Stanley knife along the bottom of the cornice a few times (sufficient to create a 2mm or so groove) should isolate it from the wall. I wouldn't think it would require support unless it gets bashed directly. How much of the cornice detail will you lose by raising the level of the wall? Probably not significant if it's anything like mine

IME its rare for the plaster to be universally and evenly ropey... chances are there are some bits much worse than others. Plaster nearer the floor will often be poorer than higher up.

I would not expect it to "flow out" from under the cornice, however if you hack off the old under the cornice and it does, then slap some bonding plaster back up the gap before you take down the next section of old plaster. In other words, treat like underpinning etc, you do bits at at a time so stuff stays supported, rather than the whole lot in one hit.

Sage advice as ever Mr R. I'm thinking the way to do it is 'with discretion'. At least the floor's down and finished now, so we have somewhere to stand while destroying it (!)

y and ready for anything serious to be dealt with. Cutting a new hole for = a back box the other day, I found the plaster is more like loose sand: I o= nly meant to cut through the wallpaper but actually went right through the = plaster with a Stanley knife.

to strip the paper off all round. It seems to me that this will just lead= to an avalanche of sand and plaster then a horrendous job of patching, so = the decision has been made to dry line the walls. This will require a bit = of careful alignment as it will have to be level with the edge of the corni= ce, which is a big old Victorian jobbie, mostly in good nick.

behind the cornice will bleed out, compromising it, so what's the best= thing to do to anticipate this?

in to shore it up. b) As a) but with a good splurge of filler/plaster or s= omething above it to stabilise things (then maybe remove the timber). c) F= ind something (PVA or whatever) I can inject along the wall to toughen it u= p in the last few inches before I start hacking at anything.

g someone has found a good solution they can share.

The plaster may well not be as bad as you think. Lime plaster is much easie= r to cut with a stanley than modern stuff. I'd be inclined to strip off a d= ecent section of wallpaper and see how it is. If it is fairly well bonded t= o the wall, but a bit crumbly, than repapering with something like

If it really needs to come off, I would fit a picture rail round the room. = Carefully cut a line at the height that the picture rail would go. Remove t= he plaster below and fit a batten to mount the rail on. You can then patch = up any damage above the batten without having matching up problems or worry= ing about the cornice. It then doesn't matter if the new plaster level does= n't match perfectly - the picture rail will disguise it.

Personally I would not dry line a victorian house - I would wet plaster bel= ow the picture rail. Dry lining tends to obscure any small problems until t= hey have turned into much bigger problems. For instance, a bit of missing = pointing shows as a damp spot with wet plaster, whereas with dry lining it = can be invisible until the plaster board disintegrates. In a new house that= shouldn't arise, but in an old one it will.

ready for anything serious to be dealt with. Cutting a new hole for a back box the other day, I found the plaster is more like loose sand: I only meant to cut through the wallpaper but actually went right through the plaster with a Stanley knife.

strip the paper off all round. It seems to me that this will just lead to an avalanche of sand and plaster then a horrendous job of patching, so the decision has been made to dry line the walls. This will require a bit of careful alignment as it will have to be level with the edge of the cornice, which is a big old Victorian jobbie, mostly in good nick.

the cornice will bleed out, compromising it, so what's the best thing to do to anticipate this?

to shore it up. b) As a) but with a good splurge of filler/plaster or something above it to stabilise things (then maybe remove the timber). c) Find something (PVA or whatever) I can inject along the wall to toughen it up in the last few inches before I start hacking at anything.

found a good solution they can share.

where water has leaked in from the roof lime plaster gets very crumbly..

but first make sure nobody put any asbestos in there in the 60sd , 70s or 80s.

In article , GMM writes

John's advice matches my own experience, patches of top coat will 'blow' off leaving a crumbly undercoat underneath but that can be stabilised with dilute pva and filled level with a layer of one coat plaster.

My approach is to stabilise the whole wall with dilute pva then fill in blown patches, levelling them off with a long straight edge[1] to avoid leaving a dip in the middle of the patch. You can then add another light coat to smooth out the surface.

With these old walls I usually double line them with a good quality 1000 grade non recycled lining paper and paint the final lining.

Well.....Derby's not so far and the Polish ones should be cheap !

The current policy is to strip the heavy textured and badly hung wallpaper = and see how much falls down with it. If the vast majority is sound, then i= t'll be patch and repair time, perhaps with a bit of pro help for a skim, b= ut if it's all like the stuff I found so far, then a light breeze should br= ing most of it down. I had been wondering about a coat of PVA, since it's = the panacea for just about everything.

An exploratory peel of the paper (when I should have been doing something e= lse) gives the impression that the bottom 1m or so is different from that a= bove it. This sort of sounds like a damp-proof treatment but this is on an= internal wall and I can't see any signs of drill holes from the injection = (which can be seen in other places). It'll be interesting to get it off an= d see what's going on!

You can't see them because it's an internal wall and the holes are drilled in the bricks behind the skirting board. If it's been chemically DP, you'll find that the bottom metre of plaster is new in all the downstairs rooms, on internal and external walls