Cornices And Coving Leave a comment

Putting up coving

preparing for putting up coving cutting cornice moulding

There’s no real ‘correct’ place in a room to start putting up a coving, if possible, start with a simple corner where the wall is longer than one length of coving. Leave the fiddley areas around chimney breast until you’ve got into the swing of it.

If using powder adhesive, mix some in accordance with the instructions – don’t mix too much as it will only be usable for 20 to 30 minutes.

Cut the first mitre joint(s), when one end of the coving is to be a straight joint, always check it for damage and trim straight if necessary. On plaster coving dampen the edges which will be fit to the wall and ceiling. Dampen the area of the wall and ceiling (this will help ensure good adhesion).

Evenly spread some adhesive along the top and bottom edges of the coving where it will be in contact with the wall and ceiling.

Position the length of coving along the marked line and with the mitre in the corner. Press the coving into place, gently pressing along the length of the coving to ensure that the adhesive is spread evenly. If the ceiling or wall is not straight, do not push hard where there is a large gap, the moulding will relax reducing adhesion.

When putting up long pieces of coving, it may begin to sag before the adhesive has set. If this happens, insert one or two nails into the wall under the bottom edge of the moulding to temporarily support it – after the adhesive has set, the nails can be removed and the holes filled. It’s sometimes necessary to put a couple of nails in the ceiling to stop the moulding ‘rolling’ forward, again, remove these after the adhesive has set and fill the holes.

Heavy plaster coving may need to be fixed with screws anyway. With the coving held in position without adhesive, carefully drill through the coving at about 1 metre spacing and into the wall. Countersink the holes in the coving, and fit wall plugs. Spread on the adhesive, reposition the coving and secure using brass screws. After the adhesive has set, the brass screw heads can be covered using filler.

Surplus adhesive pushed out of the joint should be scraped off with a pallet knife, use the surplus to fill in any gap visible. Clean off the residue with a damp sponge or cloth.

Continue to cut lengths of coving and put up working around the room carefully lining up each new piece with the adjacent piece.

After the first length goes up, each piece will have at least one joint, be it straight or mitre, put a blob of adhesive on the end so that the lengths are bonded end to end.

Preparation for putting up coving

cutting cornice moulding putting up coving

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 upto 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.

Cornices and Coving – general

What is the difference between Coving and a Cornice ? Cornice is the generic term, coving has uniform profile, cornice includes corner mouldings with patterned faces.

Coving between ceiling and wall

Coving Cornices are simple ways to finish off the look of a room and do not require any special skills to erect. Their use is especially useful when a new stud wall has been erected or a ceiling has been replaced, fitting cornice will remove the need to undertake detailed finishing of the corner where the wall and ceiling meet.

Cornice comes in a range of materials:

Plaster

heavy, easy to damage expensive

often left unpainted, this needs precautions to avoid messy hand marks when being erected can be painted with water or oil based paint

Paper Covered Gypsum or Plaster

medium weight, fairly robust can be painted with water or oil based paint

Polyurethane

light, robust

available ready coloured and patterned (such as wood effect)

can be painted with water or oil based paint

Expanded Polystyrene

light, easy to damage, cheap has the normal polystyrene bubble surface finish can be painted with water based paint (emulsion)

Timber

light, flexible and easy to use tends to be small finishing strip easy to cut to shape can be varnished or painted – best not to leave untreated as

it can discolour unevenly

Cornice also comes in a variety of sizes, it is often ‘equal/equal’, i.e. the edges are the same distance from the corner on both the wall and ceiling. The size quoted on most packages is the actual width of the cornice – a 120 mm, equal/equal cornice will come down the wall approx. 82 mm.

Choose the size to suit the room, as a general rule, larger rooms look much better with a larger cornice.

Coving is available in various uniform profiles and cornice come with various patterned faces.

Coving, with their uniform profile along the length, are easier to fit and tend to look better in modern properties (unless the general theme of the architecture or decoration is ‘old fashion’).

Some patterned cornices will add a ‘period’ feel to a room, but this can easily be spoilt by miss matching of the pattern at corners. The art of putting up patterned cornices involves getting the pattern at all corners to appear as natural points for turning. If possible, all internal corners should turn at the same part of the pattern, you cannot just put up a length hoping that the next length will reach the corn at a convenient point in the pattern. Erecting patterned cornices can be undertaken by the diy’er but care and time are necessary to give a professional looking finish.

Cornice adhesives

The choice of adhesive depends upon the material of the cornice, the options are:

Plaster powder adhesive

Needs to be mixed with water before use. Any left unused

needs to be disposed of. Suitable for plaster and paper covered gypsum/plaster.

Ready mixed plaster adhesive

Supplied in tubs ready for use. At the end of erecting cornice, just fit the lid to keep the adhesive for future use. Suitable for plaster and paper covered gypsum/plaster.

Polystyrene adhesive

Supplied in tubs ready for use. At the end of erecting cornice, just fit the lid to keep the adhesive for future use. Suitable for Polystyrene cornice.

General gap filling adhesive (NoNails and similar)

Supplied in cartridges for gun application. Suitable for Polyurethane cornices, those without solvents might be suitable for Polystyrene cornice – but check on a small piece.

Ideal for timber cornice as it avoids the need for nails

The choice between plaster powder and ready mixed plaster adhesives is ready a personal one, although using ready mixed should reduce wastage (although it is generally more expensive) and ensure a consistent consistency.

Cornice and coving corners

preparing for putting up coving putting up coving

Ready made corners

Most ranges of cornice and coving include preformed corners. With coving these are usually simply preformed internal and external corners. Corners for patterned cornices are often features in there own right so that the lengths of cornice simply butt squarely upto the corner piece – this has the advantage that there’s no need to match up the pattern at the corner.

With simple coving, it’s fairly easy to cut your own mitres as detailed below.

Cutting coving moulding

Cutting in a mitre box

Use a mitre box to accurately cut the corner mitres, make sure that the mitre box is large enough so that the two edges of the coving can fit flat against the bottom and side of the box (see right).

When using the mite box, always place the ceiling edge of each piece of coving at the bottom of the box, with the wall edge against the side towards you – on lengths requiring mitres at both ends, it helps to pencil a mark on the ceiling edge of the coving to ease identifying it when each end is cut.

Transfer wall measurements to the wall edge of the coving and carefully line this up in the mitre box.

Support lengths of plaster and gypsum cornice/coving while they are being sawn – they have some degree of flexibility but can easily break under their own weight.

Take care that you are cutting the angle in the right direction, it’s very easy to get confused.

The five basic cuts are shown to the right.

Use a fine toothed saw to cut the cornice/coving .

Smooth off the cut ends using fine glass paper.

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