Repairing Cornice and Coving
Plaster cornices, found in many older homes, can be renovated when a room is redecorated. Coving can be used in modern houses to hide cracks between walls and ceilings, as well add a decorative feature.
Restoring an old cornice
You will need:
Fine steel wool
Penknife or narrow sculptor's spatula
Plaster of Paris
Cleaning off distemper: Layers of old decoration may obscure the detailed moulding of a cornice. If the coating leaves a chalky mark on your hand when you rub it, it has probably been distempered (a form of water-soluble white-wash), so it can be washed off with water. If the distemper has been painted over with another type of paint, use a chemical paint striper before trying to remove it.
Use a garden spray to dampen only a small area of coving at a time. Allow the water to soak in and then use a penknife or sculpting tool to pick out the build-up of distemper.
Take care not to apply leverage, which could damage the moulding. On flat areas, use find steel wool, which can be bought from decorating shops.
Repairing damage: It may be possible to build up damaged areas with plaster of Paris and then reshape. Mix only a little plaster of Paris at a time because it sets quickly. Build up the moulding layer on layer and then shape it with a knife blade and fine sandpaper.
Fitting a new coving
Three types of coving are available at DIY stores and builders' suppliers. Expanded polystyrene and rigid foam plastic are lightweight and are sold in easily managed sections, so fixing is simple. Gypsum plaster coving is available in longer lengths up to 3m and is heavier, so putting it in place needs two people.
You will need:
Stepladder (two if you have a helper)
Steel tape measure
Scrape off any wallpaper or ceiling paper so that the new coving will be glued to bare plaster.
If the ceiling is uneven, use a chalked string to snap a straight line on the wall, marking the lower edge of the coving. Any gaps at ceiling level can be filled later.
Plastic coving: Some plastic coving systems come with ready-made corner pieces, so no mitre cutting is necessary. Be sure to use an adhesive that is appropriate to the type of coving you are working with.
Starting from a corner spread adhesive onto the back of each section of coving and press it into position so that it fits snugly into the angle between the wall and ceiling.
Remove any surplus adhesive while it is still wet.
If the wall or ceiling is uneven, don't force the coving to follow the surface; allow it to bridge the hollows. You can fill in the gaps with adhesive later.
Use only emulsion paint for decorating expanded polystyrene and rigid foam coving; gloss paint causes damage.
Gypsum Plaster: Plaster coving has to be mitred at the corners so that the pieces fit snugly together.
A simple template, with cutting instructions, is usually supplied to help you cut the mitres, but experiment with the template on a small piece of coving before cutting a full length because it is easy to make a mistake.
The special adhesive supplied with the coving will usually hold plaster coving in place without extra support. But for a long, heavy piece, tap masonry nails into the wall under the bottom edge and just above the top edge of the coving to support it until the adhesive dries.
Fill any gaps between the sections of coving, or along the wall or ceiling, with adhesive. Prime the paper surface of the coving with plaster primer or general-purpose primer, and decorate with emulsion paint to match the colour scheme in the room.