I would like to attempt to run a plaster coving. I've done a fair bit of plastering, and I have watched a cove being run. Can anyone tell me what plaster to use. Can I use ordinary gypsum finish plaster or do I need mix anything with it (e.g. lime) and if so what quantities?
Running a Coving
- Thread starter Merv187
- Start date
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Apologies if my query is not clear.
I want to make a coving in situ, (as opposed to a cornice, which is normally cast "off site", then fixed with adhesive or screws, to the wall and ceiling.)
The traditional way of making a cove, is to fix a wooden batten to the wall, just below the lower edge of the planned cove. Plaster is then built up in the corner (wall to ceiling) and a specially made "runner" with a metal profile of the cove is "run" along the batten, scraping away excess plaster, leaving the cove. After several passes the cove is gradually produced. It's not rocket science, but requires skill, (which in my case is a bit limited).
It also requires knowledge - which is what I am seeking! - What kind of plaster should I use? Can I use ordinary finish plaster, or does it require anything adding to it, (e.g. lime)?
Hopefully this is a little clearer.
I want to make a coving in situ, (as opposed to a cornice, which is normally cast "off site", then fixed with adhesive or screws, to the wall and ceiling.)
The traditional way of making a cove, is to fix a wooden batten to the wall, just below the lower edge of the planned cove. Plaster is then built up in the corner (wall to ceiling) and a specially made "runner" with a metal profile of the cove is "run" along the batten, scraping away excess plaster, leaving the cove. After several passes the cove is gradually produced. It's not rocket science, but requires skill, (which in my case is a bit limited).
It also requires knowledge - which is what I am seeking! - What kind of plaster should I use? Can I use ordinary finish plaster, or does it require anything adding to it, (e.g. lime)?
Hopefully this is a little clearer.
That is what I thought you meant but couldn’t imagine anyone would go to all that trouble these days. I’m afraid I can’t help you with advice but I would say categorically that finishing plaster isn’t suitable, it won’t stand being applied so thickly without cracking; maybe Bonding with a final pass using finish skim but I really don’t know. You could try talking to a local plaster moulding specialist (most areas have one) who cast these things in their workshops; I believe they use reinforced Plaster of Paris but have no idea what if anything is mixed with it.
I’ve put up all sorts of coving in the past from plain old Gyproc to really ornate & heavy castings that come in 2m lengths & require a lot of work to fix & match up. But casting in situ
I would think there are very few around these days that could/would even attempt it, is there a reason why wish to go down this route?
I’ve put up all sorts of coving in the past from plain old Gyproc to really ornate & heavy castings that come in 2m lengths & require a lot of work to fix & match up. But casting in situ
I would think there are very few around these days that could/would even attempt it, is there a reason why wish to go down this route?Sponsored Links
Richard, thanks for your comments.
I agree entirely, I have no wish to do it he hard way, - problem is I have to match an existing coving, and I only need to do a short run. The house is only two years old and the existing cove was "run" in situ. You are right, most coving is now the precast type, but there are still people doing it the "old fashioned" way. I'll try and find one, and ask their advice.
Many thanks for your help.
I agree entirely, I have no wish to do it he hard way, - problem is I have to match an existing coving, and I only need to do a short run. The house is only two years old and the existing cove was "run" in situ. You are right, most coving is now the precast type, but there are still people doing it the "old fashioned" way. I'll try and find one, and ask their advice.
Many thanks for your help.
You need lime plaster for the top coat. Last one I did (a few years ago) was done with neat lime as a top coat, mix it with water and let it go off.
The purists would use a lime/finish mix but as an amateur the pure lime does not go off as quickly but is solid enough when dry and painted.
From experience bonding is better than browning for the base coat (it sticks better).
You need to a horse (Former) ideally of metal cut to the profile with the ability to set it at two heights - low to put the base coat on (bonding), then about 3mm higher to put the top coat on. Usually done with adjustable metal runners on the horse with slots in them which slide on bolts.
You may also need a lath on the ceiling as well as the wall, and it helps if you have a piece of lath (about a foot long) fixed perpendicular to the horse to keep it square to the wall.
It is a messy job but very rewarding.
The reason for doing it - it beats anything you can buy off the shelf. . . , When your visitors look at it and ask where you got it from . . . , or where the joins are . . . , when the more knowledgeable ones ask how you got it to go round the curves . . . . .
The purists would use a lime/finish mix but as an amateur the pure lime does not go off as quickly but is solid enough when dry and painted.
From experience bonding is better than browning for the base coat (it sticks better).
You need to a horse (Former) ideally of metal cut to the profile with the ability to set it at two heights - low to put the base coat on (bonding), then about 3mm higher to put the top coat on. Usually done with adjustable metal runners on the horse with slots in them which slide on bolts.
You may also need a lath on the ceiling as well as the wall, and it helps if you have a piece of lath (about a foot long) fixed perpendicular to the horse to keep it square to the wall.
It is a messy job but very rewarding.
The reason for doing it - it beats anything you can buy off the shelf. . . , When your visitors look at it and ask where you got it from . . . , or where the joins are . . . , when the more knowledgeable ones ask how you got it to go round the curves . . . . .
you can take a profile of your original cornice take it into any fibrous workshop and they will run you a length on a bench, its cheaper and easier. if you go for it yourself you will need to make the running mould which involves taking a profile anyway. Once you have made the running mould you fix what is called a muffle onto the mould which is done using plaster or a piece of metal. Imagine the shape your running and your looking at the mould the muffle will fit on and leave say 3-5mm of the finished mould hidden. Run it round the room using light weight plaster or lime sand morter which will give you the core of the mould. if its a massive cornice strips of laths are used with eml fixed then the same prosedure with the muffled running mould, this reduces the weight, make sure you scratch the core to take the finish. The finish is usually plaster of paris with a retarder added but this stuff sets quick. This is a specialist job not to be taken lightly so i would go with the first option.
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