Coving, also sometimes known as Cornice or Crown Mouldings, serves two main purposes in a room. The first is to conceal the join between wall and ceiling and the second is to add a decorative touch to the room. It is fairly simple to fit coving and this is certainly a job that can be tackled by even a new DIY-er.
You can buy coving in a variety of styles and sizes, but it is generally only available in one of four materials. The most popular nowadays are probably Polystyrene or paper-covered polystyrene. This is easy to work with and requires the least amount of effort to fit (can simply be glued into place) due to its lack of weight. Wood and plaster coving can be moulded for added decorative appeal, but often require extra measures to be taken during fitting (often need to be nailed as well as glued).
Take a short length (about 1.5 metres) of your chosen coving and use this to mark a pencil line all the way around the room. Take your time to ensure the line is continuous and straight as this will be you guide when fitting the coving. If you are fitting polystyrene (or paper-covered polystyrene) you will need to remove a wall coverings between the pencil line and ceiling, indeed this is good practice when fitting any type of coving. To do this, run a trimming knife along the line and peel the paper strip away using a stripping knife and wallpaper stripper if needed. Lightly score the stripped area of the wall and the corresponding area of the ceiling to give the coving adhesive something to key to.
Polystyrene and plaster coving are often available with ready-made corner pieces, meaning you don’t have to fiddle about cutting mitres. Corner pieces for timber coving are also available, but not as often as with the other two types. Some coving comes complete with a mitre-cutting template or even a special jig. If you have to cut the mitres yourself, you will need to use a deep mitre box and a fine-toothed Panel or Tenon Saw (or a sharp Trimming Knife for polystyrene). Take your time and be prepared to make adjustments for uneven walls.
Fitting Polystyrene Coving
If you have ready-made corner pieces, fit these first. Now pick a corner and work towards the next corner. This allows you to make the best use of the coving lengths you have. The piece between the last full length and the next corner will undoubtedly need trimming to fit. Use a sharp trimming knife for this. Make sure you use adhesive recommended by the coving manufacturer to fit polystyrene coving, as some adhesives will eat through this material. If the walls are particularly uneven, try using tile adhesive to give a thicker bed for the coving to sit in.
Fitting Plaster Coving
As with polystyrene coving, start in the corners if you have ready-made pieces. Plaster coving requires special adhesive, spread on the back edges of the mouldings. Unless using very thin plaster coving, wire nails will need to be used to hold the coving in place as the adhesive dries. Tap these in along the top and bottom edge of the coving (but not through it) to act as a support. Once the adhesive is completely dry, remove the nails and fill any holes or gaps in the corner joints with plaster filler.
Fitting Timber Coving
Timber coving can be fitted with adhesive and supporting nails exactly like plaster coving, but it is often better to just use panel pins driven through the wood. When using panel pins, make sure you choose a size that allows at least 20mm to penetrate the wall behind the coving. Once the coving is in place, go along each length with a nail punch and drive each nail head below the surface of the wood. You can then use wood filler of a matching colour to hide the holes.
Polystyrene Coving is usually left untreated, but can be painted if you wish to. Paper-covered polystyrene coving is usually painted once in place, as is plaster coving. Timber coving can be painted, but is usually stained or varnished.