While in the loft I lifted some of the insulation to find that virtually all the 'key' bits of plaster that squish through the lath were detached and just littering the surface. However the ceilings seem to be staying put. I can't think what's holding them up! Do I have a serious problem please? The house is 1930's. Thanks Peter
Is it possible the ceilings have been plasterboarded at some time? This is often put directly over the top of the old lath and plaster?
From below, can you push the ceiling and feel a "live" movement? If so, then they are probably held up by luck ;-) Tim Hardisty. Remove HAT before replying
Suggest fitting HAT before pushing up on the ceiling too ;-)
There's a serious potential problem, aye. I think it's the plaster equivalent of surface tension holding the ceiling up - if it's damaged at any point it could cause a collapse.
All is not lost though. Since you obviously have access to the laths themselves you can repair the ceiling from behind by using a form of plaster of paris. I don't know how expensive that might end up being but if you've got any original decorative features on the ceiling its pretty much the only way I've heard of keeping 'em intact.
Here's a bit of detail:
Here's another one:
cheers
witchy/binarydinosaurs
If its still in place, its still in place. Its when lumps fall on your head that you have a serious problem, and as I understand it you dont have that.
Regards, NT
What makes you think the plaster is not bonded to the lath ? After all, that's all there was to hold it up until the "nibs" dried.
Slightly more seriously, the ceiling will be weakened by losing a significant amount of the "nibs" that do provide some structural strength. As long as you don't start having parties in the attic, it'll be fine. Try to walk around on the joists carefully if you don't have anything lying on them to spread the load.
It might be for first few days, but after a few humidity changes, it certainly won't be. Someone may have already fixed it by pouring diluted PVA over the laths and plaster, which will bond them. If not, that's something you might do, but I wouldn't risk it without supporting the ceiling from underneath while it dries. This is a common way of repairing a lath and plaster ceiling once the plaster does come away from the laths, providing it hasn't fallen down yet. A board supported by some slightly over-long poles is used to push it back in place, and diluted PVA poured over the back to soak in and set.
Suction.
The adhesion between the old plaster and the laths is amazing and it is highly unlikely that it will come down around your ears. With all that old horse and goat hair spread through it, it is even more amazing how the got it up on the ceiling in the first place. :-))
The Collins DIY manual suggests applying watered down PVA on onto the lathes to give it more strength.
I doubt it - if you open up the bottom of a lath and plaster wall you'll find it full of these 'nibs'. The plaster sticks to the wood laths.
The easy way to tell if it's gone 'live' is by pushing it between the joists. One in good condition will be firm - a poor one will bend easily.
Peter,
As a temporary expedient some years ago I propped up a lath and plaster ceiling with acrow props and 8 x 4 chipboard, and poured neat sloppy plaster under the upstairs floor boards to hold it all together. When I came to pull it all down a few months later it was VERY well bonded !
Andrew
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