How to Fit Plaster Coving, Step by Step

To fit plaster coving, you mark guide lines on the wall and ceiling, cut each length to size in a mitre box, key and dampen the surfaces, spread coving adhesive along the back edges, press each length onto the lines, hold it with a couple of temporary nails while the adhesive sets, then fill the joints and prime and paint. That is the method manufacturers such as British Gypsum set out for their plaster cove, and it suits most lightweight plaster coving in an ordinary room.

Heavier fibrous plaster cornice is a different job, and we explain where that line sits further down. If you would rather not do it yourself, Zavoré supplies plaster coving on its own or fits it for you. See our plaster cornice and coving page for both.

What you need

• Plaster coving, with some spare for waste and test cuts.
• The coving adhesive recommended by the coving maker.
• A coving mitre box or mitre block and a fine toothed saw.
• A tape measure, pencil, spirit level and a short offcut of coving to mark from.
• A filling knife or small trowel, a sponge, a bucket of clean water and fine abrasive paper.
• Small nails for temporary support, and a stable platform or stepladder rather than a chair.

Preparing and measuring

Prepare the surfaces

British Gypsum's instructions for its plaster cove ask for wall and ceiling backgrounds that are sound, clean and dry, with any wallpaper removed where the coving will sit. Scratch painted or plastered areas that the coving will touch to give the adhesive a key, then brush away dust and loose material. If the background is very dry, dampen it with a clean sponge just before you apply adhesive, so it does not draw the water out too fast.

Mark guide lines

Draw a pencil line along the wall and another along the ceiling to show where the edges of the coving will land. The maker gives these distances for each profile. For its 127mm cove, for example, British Gypsum gives 83mm down the wall and 83mm across the ceiling. If you have no figure, hold an offcut in the corner and mark both edges at intervals, then join the marks with a straight edge.

Measure each wall

Measure every wall at ceiling height rather than at floor level, because old rooms are rarely square. Plan the run so joints fall away from the eye line from the door, and avoid finishing a wall with a short piece. Write the measurements down and mark which end of each length is an internal corner, an external corner or a straight joint.

Cutting the mitres

Cut each length with a fine toothed saw in a coving mitre box or block. Most boxes are marked for internal and external corners, left and right, and show which edge of the coving sits against the base. Follow those markings exactly.

• Internal corners. These are the ordinary corners of a room, where two walls meet and the coving turns inwards. They are the most common.
• External corners. These wrap round a chimney breast or a projecting wall.
• Straight joints. Where one length meets the next along a wall, a square butt joint is usual.

Cut a pair of test pieces from offcuts first and offer them up to the corner. If the walls are out of square, a small gap can be filled later, but a large one means adjusting the cut. Some makers also sell ready cut corner pieces, which take much of the risk out of the job.

Fixing the coving

Apply the adhesive

Mix the adhesive as the maker directs and in small batches, because it sets. British Gypsum asks for a bed about 3mm thick on both surfaces of the cove that touch the wall and the ceiling. Butter the cut ends too, so each length bonds to the next. Press the length firmly onto your guide lines so it is in contact along its whole length, and wipe away excess adhesive with a damp sponge before it sets.

Support it while it sets

Tap two small nails into the wall just below the bottom edge of each length to hold it while the adhesive sets, and take them out once it has. On uneven backgrounds, British Gypsum recommends non rusting screws into plugs as a mechanical fixing. Long lengths are far easier to handle with a second pair of hands.

Filling joints and painting

Use the excess adhesive to fill the mitres and joints as you go, and strike them off neatly. Once everything is dry, fill any remaining gaps, let the filler dry, then sand the joints and corners smooth with fine abrasive paper and dust off.

Before painting, follow the coving maker's advice on priming. British Gypsum, for example, specifies a primer on its cove before the decorative coat. Most decorators then paint the ceiling and coving together, cut in a clean line along the bottom edge, and paint the walls last.

When to call a professional

Plain, light plaster coving in a modern room is a fair DIY job. Some jobs are better left to coving fitters or a plasterer.

• Heavy fibrous plaster cornice. Deep profiles are heavy and usually need screwing back to the structure as well as bonding.
• Ornate enrichments. Repeating ornament has to line up at every mitre and joint, which takes planning and experience.
• Old or uneven ceilings. Lath and plaster ceilings with cracks, bulges or loose areas need to be assessed before anything is fixed to them.
• Matching an existing profile. New lengths made to match period cornice are specialist work. Our guide to Victorian, Georgian and Edwardian coving explains how it is done.
• Listed buildings. Speak to your local authority before you alter or replace historic plasterwork.
• High ceilings and stairwells. Working safely at height needs proper access equipment.

Questions we get asked

Can I fit plaster coving on my own?

Short, light lengths, yes, with care. Long lengths are awkward to hold and bed evenly alone, so a second person makes the job much easier and safer.

Does coving hide the crack between the wall and the ceiling?

It covers the joint, but it is worth finding out why the crack is there first. If the building is still moving, the coving joints may crack in turn.

How long before I can paint the coving?

Wait until the adhesive and filler are fully dry, and follow the drying times printed on the products you used. Painting too soon can leave marks over the joints.

Do you fit coving or only supply it?

Both. Zavoré supplies plaster coving, cornice and plaster ceiling roses on their own for your own fitter, or supplies and fits them.

Where to go next. See the profiles we supply and fit on our plaster cornice and coving page, or send your room sizes and a few photos through our contact page for a supply only or fitted quote.