Coving - preparation walls and ceilings
Coving is fairly easy to put up given a planned approach, patterned cornice is harder to put up because of the need to match the pattern at corners.
Always read any manufacturers instructions supplied with the coving, while the following may be more comprehensive than most manufacturers instructions, there may be specific considerations particular to the coving you have purchased.
When putting up coving, it's worth while working from a stable platform, you'll have enough to concentrate on putting up the coving, without worrying about where you are going to put your feet.
As coving needs to be stuck to firm, sound surfaces, all wallpaper, emulsion paint, distemper and loose plaster need to be removed from both the wall and ceiling - so try to fit coving before you redecorate the room.
Read the instructions (if any) supplied with the coving, this should give you the distance on the wall and ceiling for the edge from the corner. If there are no instructions, cut off a small length of the coving (about 100 mm (4 inches)) and use this against a corner to determine the distances.
Having removed all wallpaper and unsound surface from the ceiling and wall along the line of the coving, use the distances from the corner to mark the wall and ceiling with a pencil to indicate the edges - mark on both sides of each corner.
Put up a string line between corner marks and use rule to check the distance along the line between line and corner to check for variation. With most coving, variations up to about 3 mm can be accommodated by the adhesive, but if the distance between line and corner is less than the coving distance, you'll either have to trim the coving edge or adjust the line down on both sides of the corner.
Don't worry too much about getting the line level, it's more important to get the line parallel to the ceiling and wall.
Having gone completely around the room, marking both ceiling and wall corners, replace the string on each edge, mark the wall/ceiling at regular points along the line, remove the string and join up the marked points using a straight edge.
Within the marked area, use a sharp knife to roughen the surfaces of the wall and ceiling with criss-cross scratches to provide a key for the adhesive. Use a clean brush to remove any dust.