To fit coving, mark a guide line on the wall and ceiling, cut the internal and external corners with a mitre box, and fix the lengths with coving adhesive. Then fill the joints and gaps, and prime and paint once the adhesive has set.
Most of that is straightforward. The corners are where people get stuck, especially in older houses where walls aren’t square. This guide from PDS Painting Birmingham takes you through each step, including how to paint coving, and is one of our painting and decorating guides.
Types of Coving: Polystyrene, Polyurethane and Plaster
| Type | Weight | Ease of cutting and fitting | Finish | Painting notes |
|---|---|---|---|---|
| Polystyrene | Very light | Easy to cut; dents easily | Softer edges and detail | Water-based paint only - solvent-based paint can melt it |
| Polyurethane / resin | Light | Easy to cut; some ranges flex on uneven walls | Crisp, sharp detail | Usually takes emulsion well; check the maker’s advice |
| Gypsum / plaster | Heavy | Harder to cut cleanly; needs support while setting | Crisp, traditional look | Bare plaster needs priming, like new plaster |
Polystyrene is cheap and forgiving but can look a little soft, especially on wider profiles. Polyurethane gives sharper detail and is good for older rooms with wavy walls. Gypsum coving has the traditional look many period homes suit, but it is heavier and less forgiving of mistakes.
Ornate period cornice, with deep mouldings and decorative detail, is a different job from fitting a run of coving and is not covered here.
Tools and Materials You Need
- Coving lengths, plus a spare length for mistakes
- Mitre box and a fine-tooth saw (or the cutting template supplied with the coving)
- Coving adhesive
- Filling knife
- Tape measure and pencil
- Spirit level or chalk line
- Stepladder or a safe working platform
- Masking nails or pins for temporary support
- Damp sponge and a bucket of clean water
- Decorator’s caulk or filler
How to Fit Coving, Step by Step
Work clockwise round the room, starting in a corner.
Step 1: Measure and Mark Guide Lines
Take a short offcut of your coving and hold it in place at the wall-ceiling junction. Mark where its bottom edge sits on the wall and where its top edge sits on the ceiling. Repeat every metre or so round the room.
Join the marks with a straight line, using a spirit level or a chalk line. These lines show exactly where each length sits, so the coving runs straight even if the ceiling doesn’t.
As you go, note where the ceiling dips or the wall bows. Small variations can be filled later; larger ones will need extra care at the fixing stage.
Step 2: Cut the Internal and External Corners
This is where most coving goes wrong. Set the coving in the mitre box upside down, as if the base of the box were the ceiling: the edge that will touch the ceiling sits on the base, and the edge that will touch the wall rests against the back of the box. Then cut using the correct slot for a left or right corner.
Use a simple check before you cut. On an internal corner, the wall edge of the coving is longer than the ceiling edge. On an external corner, such as a chimney breast, the ceiling edge is longer. If your cut is the other way round, it is the wrong mitre.
Cut and fit the corners first, then fill the straight runs between them. That way any trimming happens on a plain length, not a fiddly corner.
Mitre boxes assume a 90-degree corner. Many older walls are a degree or two out, which leaves a gap at the mitre. Dry-fit both pieces, then trim a fraction off by hand with a sharp knife or sanding block until they meet. In older homes with out-of-square corners and uneven ceilings, this is where many people decide on professional coving installation in Birmingham.
Step 3: Prepare the Surfaces
Coving adhesive needs a sound surface. Scrape off any loose paint, flaking emulsion or wallpaper in the strip between your guide lines - the adhesive is only as strong as what it’s stuck to.
Score painted surfaces with a scraper or knife to give the adhesive a key, then dust off. If the adhesive instructions say so, dampen porous plaster so it doesn’t pull the moisture out too quickly. The same principles apply as when preparing walls for painting.
Step 4: Fix the Coving
Butter adhesive along both contact edges on the back of the length - the edge that meets the wall and the edge that meets the ceiling. Press it firmly into place between the guide lines so a little adhesive squeezes out.
Lighter coving usually holds once pressed. Heavier lengths, especially gypsum, need masking nails or pins tapped in just below and above to support them until the adhesive grabs.
Where two straight lengths meet, apply adhesive to the ends as well and push them together for a tight butt joint. Wipe away squeeze-out with a damp sponge straight away; dried adhesive is far harder to remove neatly. Leave it to set for the time on the tub.
Step 5: Fill the Joints and Gaps
Once the coving is firmly fixed, fill the mitres, butt joints and any gaps along the wall and ceiling edges. Use leftover adhesive, a fine filler or flexible caulk, and smooth it with a wet finger or filling knife for a clean line.
When the adhesive has set, remove the pins and fill the holes. Give any filled joints a light sand once dry if needed.
How to Paint Coving
Let the adhesive and filler set fully before painting. Paint over adhesive that is still curing and it can crack or show through.
Bare plaster and gypsum coving is porous, like a freshly plastered wall. Prime it with the manufacturer’s recommended primer or a mist coat on new plaster so the topcoats don’t soak in unevenly. Polystyrene coving must only have water-based paint.
Most people paint coving the same colour as the ceiling, or a crisp white to frame a coloured ceiling. Use a small angled brush to cut in along both edges and apply two coats of emulsion.
The usual order is ceiling first, then coving, then walls. That way any marks land on surfaces you haven’t painted yet, the same reasoning behind how we paint ceilings. If the walls are already done, tape the top edge of the wall before painting the coving.
New coving often prompts a full refresh of the room. If you’d rather hand over the lot, our interior painting and decorating covers ceilings, walls and woodwork.
Common Coving Mistakes
- Cutting the mitre the wrong way round - check which edge should be longer before every cut.
- Fixing to loose paint or wallpaper - the coving comes away with the old finish.
- No guide line - the coving follows every dip in the ceiling and looks wavy.
- Not wiping adhesive while it’s wet - dried lumps are hard to clean off without damage.
- Solvent-based paint on polystyrene - it can soften or melt the coving.
- Painting before the adhesive has set - joints crack and the paint shows it.
- Ignoring cracks that reopen at the wall-ceiling joint - use flexible caulk, not rigid filler.
When to Call a Coving Installer
Coving is a reasonable DIY job in a modern room with square corners and a flat ceiling. It gets much harder with uneven ceilings and out-of-square walls, heavy plaster coving that needs support, high ceilings and stairwells, or runs right through a house. Replacing a damaged section to match existing coving can also be tricky.
If the ceiling itself is cracked, sagging or needs re-skimming, you’ll need a plasterer before the coving goes up. Once the surfaces are sound, you can have coving fitted and painted by PDS Painting.
Related Guides
- Preparing walls for painting - cleaning, filling and sanding before you paint.
- Mist coats and painting new plaster - how to seal bare plaster before topcoats.
- How we paint ceilings - our method, start to finish.
See all painting and decorating guides, or call 0121 752 9229 to ask for a coving quote.
Coving questions
Do you paint coving before or after fitting?
Usually after. Filled joints, mitres and pin holes all need painting, so it makes sense to paint the whole run once everything has set. Some people prime bare plaster coving before fitting to save a step, then finish with the topcoats once it is up and filled.
What paint should I use on coving?
Emulsion, usually the same colour as the ceiling or a clean white. Bare plaster or gypsum coving needs a mist coat or the primer the manufacturer recommends first. Polystyrene coving must only have water-based paint, because solvent-based paint can soften or melt it. See our guide to the mist coat on new plaster.
How do you cut coving corners without a mitre box?
Many coving packs include a paper or card template you wrap around the length to mark the angle. You can also mark the cut by holding the coving in place and marking where it meets the guide lines on the wall and ceiling. For beginners, a mitre box is far more reliable and worth the small cost.
Can you fit coving on an uneven ceiling?
Small dips can be filled with adhesive or caulk once the coving is up. Larger ones need a flexible coving that follows the line, or careful scribing and packing, which takes practice. Where ceilings are badly uneven, that is where a professional coving installation in Birmingham is worth considering.
How long does coving adhesive take to dry?
Most coving adhesives grab within minutes, which is why you can press a length into place and it stays. Full setting takes much longer, and the tub gives the time before you can fill over it and paint. Use pins to hold heavier lengths until it has set, and keep the room at a normal temperature.
Why has a crack appeared between my coving and the ceiling?
Usually seasonal movement in the ceiling or walls, or adhesive that didn't bond to a loose painted surface. If the coving is still firmly fixed, rake out the crack, fill it with flexible caulk and repaint. If the coving has come away, take it down, prepare the surfaces and refix it.