Coving or Cornice is the concave or convex moulding that runs across the top of your interior walls neatening the join between the wall and ceiling while simultaneously giving your home an injection of period or modern elegance.
Traditionally coving is made of plaster, hessian & wooden laths, although there are modern examples made from polystyrene and paper-wrapped materials these are never as hard waring. If your room had the original coving ripped out, Plaster coving will restore the room's period feel and add value to your home (picture rails and ceiling roses have the same effect).
When shopping for coving bear in mind that smaller rooms require narrower coving. Always buy more than your room size. The room corners are particularly tricky and involve "mitres" - angled pieces of coving you have to cut with a panel saw, ideally using a mitre block.
To put up a section of coving, you'll need "coving adhesive", which either comes ready-mixed or in powder form mixed by hand. Make sure the surfaces of your wall and ceiling are dry, clean and sound, and then create guidelines around the room by marking the walls with a chalk line or drawing a pencil line above and below where the coving is to go, having checked that there are no cables or pipes behind the wall, tap nails onto the wall guidelines ready to rest the Cornice on top.
Now use a trowel or scraper to spread the adhesive around the back edges of the coving. Push the section into place onto the nailed wall guidelines; now tap nails into the ceiling, just above the top edge to support the coving as the adhesive dries (any excess can easily be wiped off with a damp sponge). Make sure the entire length of the coving makes contact with the wall and ceiling.
Use the surplus adhesive to fill any gaps in the corners or the joins at each end. If the coving moves under its own weight, you've spread the adhesive too thinly, so apply another generous coating; you can remove the nails when the adhesive becomes set. If you are fixing coving on an uneven surface you may have to reinforce the fitting with countersunk screws driven into wall. When you're done, go around the room filling any gaps with adhesive, then sand the joints and corners using wet or dry abrasive paper 180s or 120s grade.
The above should be used as a guild line only, if in doubt, contact a professional fitter.