How do I fix coving that has come away from the ceiling?

Coving usually fails at the ceiling edge, because that is where the adhesive was thinnest and where the ceiling flexes most. It rarely means the whole run is bad.

What you'll need

• Coving adhesive
• A filling knife and a scraper
• Panel pins or plasterboard screws
• A joist detector
• A damp brush and sponge
• Fine filler

Step by step

1. Find out how far it has come away.Press gently along the run. The loose section is usually shorter than it looks. Mark the ends of the failed length.
2. Establish what the coving is.Gypsum plaster coving is heavy and rigid. Polystyrene and polyurethane are light and use different adhesives. The wrong adhesive is a common cause of failure.
3. Ease it open gently.A thin scraper or a filling knife worked into the gap. Just enough to get adhesive behind — levering hard cracks gypsum coving and it will not go back.
4. Scrape out the old adhesive.As much as you can reach from both the coving back and the ceiling. New adhesive on old, dusty adhesive is a repeat of the original failure.
5. Score and dampen gypsum surfaces.A scored back on plaster coving and a lightly dampened ceiling give the adhesive something to bond to. Dry dusty gypsum absorbs the water and the bond never develops.
6. Use plenty of adhesive.A continuous bead along both contact faces, not dabs. Coving adhesive is meant to fill the gap and bed the coving, and excess squeezes out and is wiped off.
7. Add a mechanical fixing.This is what people miss. Two or three plasterboard screws through the coving into the ceiling joists, or panel pins into the wall below the coving, hold it while the adhesive cures.
8. Find the joists first.A screw into plasterboard alone holds a fraction of what one into a joist does, and coving is heavy.
9. Support it while it sets.Pins, props or a batten. Several hours, longer in a cold room. Adhesive that is loaded before it sets simply fails again.
10. Wipe the squeeze-out immediately.A damp brush along both edges while it is wet. Set adhesive on the ceiling has to be sanded off, which damages the paint.
11. Fill the top and bottom joints.A neat line of adhesive or fine filler along both edges, smoothed with a damp brush. That line is what makes coving look fitted rather than stuck on.
12. Countersink and fill the screws.Set the heads below the surface and fill over them, then sand and paint.

Tips

• Screws into the joists are the single change that stops coving falling off again. Almost nobody uses them and almost everybody should.
• If the coving has come away because the ceiling is sagging, fix the ceiling first. Refixing coving to a moving ceiling is temporary.
• Polystyrene coving needs a specific adhesive — solvent-based products dissolve it. Check the tube.

Common mistakes

• Refixing over the old adhesive — The failure surface is usually the old adhesive itself, which is dusty and has lost its bond. New adhesive applied on top has the same weak layer underneath it, and the coving drops again within a year.
• Relying on adhesive alone on a long run — Gypsum coving is heavy and the adhesive has to hold it for hours while it cures. Without a temporary or permanent mechanical fixing, gravity wins in the first half hour and the whole run sags.

If it doesn't work

Questions people ask