Salvaging plaster coving before boarding ceiling

[c0wb0y]

Hey folks, my Edwardian house still has the original large coving on a lath/plaster ceiling. Without going into detail, the ceiling absolutely must come down (think rain damage!) but it'd be a shame for the coving to go down with it. I can't overboard either as I'd lose a lot of detailing in the coving's end profile (due to thickness of plasterboard).

Prying the plaster off didn't work so wondered if there was a way to cut out long sections in situ using a multitool or even an upside-down circular saw (to include the lath/plaster beneath it). I'd then be looking to somehow 'reattach' the sections to a newly plasterboarded ceiling? Am I bonkers?

Googling online reveals the same plaster coving costing over £500 per room so its good stuff and I'd like to salvage/restore it.

Thoughts please

 

[Deleted member 174758]

You'd think it was easy, however, my own experience of dealing with these mouldings in Victorian and Edwardian buildings is that they are a mixture of run in situ plaster, timber and cast plaster mouldings with the cast plaster being very much in the minority. The run in situ mouldings (at least on domestic size properties) often have a build-up of fairly coarse mortar-like material, sometimes including broken brick, etc to make up the volume at minimal cost, with a fairly thin (1 to 1-1/2in, often much thinner) skim of plaster of Paris at the surface where the actual profile is formed. This was done because plaster of Paris was relatively expensive 100 odd years ago. P of P also doesn't work well when applied in thick layers, with a tendency to crack unless built up in thin layers and supported by a mesh fabric (think about a cast on a limb). Finicky details such as ornate ceiling roses, fancy corner blocks, shields, etc were often pre-cast off site or just bought-in ready made and added in. You also find another technique where a timber ground is clad with laths, lime plastered then the mouldings are run atop that. Seen those o offered ceilings most often, but they are used elsewhere. They are all but impossible to remove without destroying them.

Timber mouldings up to about12in/300mm are sometimes found, although I associate them more with shop interiors than domestic settings (they would have been far faster to install than any form of plaster and could be stained or painted immediately).

The modern technique of plaster casting lengths of moulding appears to have become fashionable after WWI and is more often found in buildings from the 20s and 30s.

I'd therefore suggest trying to get a small piece off to see what you are dealing with. If it is run in situ it will be almost impossible to remove anything other than small sections at a time and it won't necessarily go back all that well. For this reason even on conservation jobs it is easier and cheaper to re-run the mouldings in situ or to to a pre-cast replacement

 

[johnny2007]

I have done it a long time ago and it's a bit of a pain, but worth it.
You will need to cut the ceiling along the coving line with multitool or reciprocating saw/hand saw of smaller size.
Then you will need to create support for the new ceiling by adding timber between ceiling joists where needed, alongside and/or across the coving.
This saves the coving and its details because the thickness of existing lath and plaster left under the coving will be more or less that of new plasterboard.
If coving needs supporting after cutting the ceiling, make sure you add the pieces of timber so you can put a few screws in the coving to secure it.
Then it can be decorated so to hide the screws.