What is Coving & Cornice?
Decorative coving/cornice mouldings add a finishing artistic touch at the wall/ceiling angle to make a room look complete, transforming a visually plain look into one of style and substance. The term coving tends to be used to describe mouldings with a uniform projection/depth, whereas cornice is usually more ornate and of unequal measurements. However at the end of the day, they both serve the same purpose and coving is usually the generic descriptive term. Whilst only basic DIY skills are needed for installation, coving can be made in differing materials that will make life easier or harder for the average installer.
Types and prices
Coving comes in various different materials from cheap and cheerful polystyrene to plaster which is more attractive but immensely heavy and very difficult to install.
Polystyrene coving is very light and soft and is easily damaged. It also has rounded edges so doesn’t look very ‘real’. It is very cheap - and looks it.
Paper covered gypsum coving is heavier and the smooth paper covering gives a much better base for painting. It is cheap but only available in the standard smooth ‘C-shape’ (4” or 5”) which was popular in many houses from the 1950’s onwards. Most people now want something a little more stylish.
Plaster coving is the most traditional option offering plenty of period designs and patterns. Although it has a good finish, it is more expensive, extremely heavy and quite brittle, so is unsuitable for DIY fixing. Due to its weight it must also be screwed securely to the wall to prevent it falling away.. Movement in the wall/ceiling can also potentially cause unsightly cracks to appear.
Recent years have seen the introduction of high quality hardened polyurethane based mouldings. These products combine the best of all materials with none of the disadvantages. They are very light, but also very strong, and mitre cleanly rather like a piece of light wood. Being produced in high pressure metal moulds they are able to show off the same incredible detailing of plaster, but with the advantage that anyone with basic skills can install. Most installers now favour this material due to the wide range of beautiful designs that are available, having the visual appearance of plaster but the time and cost saving benefits of quick and simple installation. In the UK, Davuka GRP Ltd are the leading suppliers of polyurethane based mouldings with a substantial range of all styles. Pricing is on a par with plaster products.
Cut off a small section to use as a template. Use this piece to mark the top and bottom edges on the walls and ceiling all around the room. Make the marks at regular intervals so that you can join them with a straight edge.
Connect the marks with a straight edge (the edge of a spirit level is ideal) and remove any wallpaper or loose paint. Make criss-cross scratches between the guide lines with a craft knife to provide a key for the adhesive. It is sometimes helpful to add pins along the wall line to guide the coving into place and to also support it whilst the adhesive dries.
Use a mitre box to help cut an accurate mitre at the end of the first piece of coving. Take care to place the cornice the right way around and always double check that you are cutting the angle in the correct direction.
If your wall length is less than that of a piece of the cornice, you will need to accurately measure the wall and cut the other end with an appropriate mitre as well. This will normally be the reverse angle. When making the cuts, use a fine-toothed saw, and sand the edges smooth with some sandpaper. Take your time with the mitres as the neater you do these, the less work you will have later on.
With a filling knife or caulking gun, spread an even layer of adhesive over the top and bottom of the back of the moulding - the areas that will be in contact with the walls and ceiling.
Press the cornice into place and line up the bottom edge with the pencil guide line. Press gently along the whole length so that the adhesive sticks evenly.
Supporting the coving
Long lengths of coving may sag or fall off before the adhesive has set. Temporarily support the bottom edge with one or two galvanised nails. You can remove these and fill the holes when the adhesive has dried. Depending on the type of cornice, you might also find it beneficial to put a couple of these nails in the ceiling as well to stop the cornice rolling forward.
Use a damp paintbrush to remove any adhesive that oozes out from the top and bottom edges and to smooth the joint line. Fill any gaps with more adhesive.
Continuing around the room, you can simply butt one piece up to the previous one with a straight join. Often, however, a neater, less obvious joint can be produced by 'splicing' the two. To do this, you will need to mitre the end of the first piece before fixing in place. With the second piece, simply cut the same mitre at the beginning of the length. This second piece will either be a full length, in which case you will need to repeat the joining process, or cut to size at a corner, in which case it will need to be mitred accordingly.
If you have any 'external' corners in the room, you will need to cut the two ends which join here with mitres in the opposite direction. This often causes problems since, not only have you got to remember to cut the angle the right way, but also the point to which you measure is different. The best way to remember and get it right is to always measure for the bottom edge of the cornice on external angles and the top edge for internal angles. At the same time, make a note in which direction the angle should be cut.
If your walls are slightly bowed you can still add cornice as the material will be flexible enough to be slightly curved to match the wall. However, to keep it in place you should plug and screw it to the wall with brass screws. Countersink the heads and fill the holes with a dab of adhesive. Don't use steel screws as these will rust and discolour the surface.
Try to make as few joints on the walls as possible. It's worth buying an extra full-length piece of cornice rather than use up two shorter sections - the result will be neater.
Fixing heavy cornice
Very heavy plaster cornice may need to be fixed with brass screws at 1m spacings to provide adequate support. Hold the cornice in position and drill carefully through the cornice and into the wall. Add wall plugs, spread on the adhesive and screw into place.
Most plaster type cornice is fairly fragile so take care when lifting it so that it doesn't snap. Get the help of an assistant, particularly with the heavier plaster type.
It is always best to work from a platform rather than simply on a stepladder. Set up a safe and stable working platform using two pairs of steps or hop-ups and a suitable scaffold board. Be sure that the board is properly supported and strong enough to take your weight. This will enable you to concentrate on fixing the cornice, rather than having to continually move your steps.
Repairing old cornice
If you are lucky enough to have original coving, you can remove clogged paint with a chemical stripper.
Cover the floor with plenty of paper and wear safety goggles and gloves.
Dab on the stripper with a brush and work well into any mouldings. Leave to work and then remove the paint with a nylon scouring pad and an old screwdriver. Take care not to damage the plasterwork. Fill any cracks with a plaster filler. If you're patient, you can also re-build any small missing details as well.
- For more information on polyurethane based mouldings: Davuka GRP Ltd