How to fit Plaster Cornice / Coving to your home or room
Cut off a small 100mm length of cornice (also known as coving) to use as a template. Use this piece to mark the top and bottom edges of the cornice / coving on the walls and ceiling all around the room. Make the marks at regular intervals.
Remove any wallpaper or loose paint and plaster from the area. Make criss-cross scratches between the guidelines with a stanley knife to provide a key for the adhesive if necessary.
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. It is always best to cut from a stable platform set at a suitable height; this will make things easier.
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 standard wood saw. Take your time with the mitres as the neater you do these, the less work you will have later on.
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 guideline. Press gently along the whole length so that the adhesive sticks evenly.
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. It is also advisable to use screws aswell. Countersink the screws first by twisting a Stanley knife into the face.
Use a paint scraper 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 then use a wet paintbrush to finish.
Continuing around the room, you can simply butt one piece up to the previous one with a straight join.
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.
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.
Very heavy plaster cornice will need to be fixed with screws at 500mm spacings to provide adequate support
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.