Fitting ceiling coving: cutting, gluing and painting cleanly

Coving fitted between the ceiling and the walls gives an elegant finish, hides the corner defects and structures the room without major work. Polystyrene or polyurethane models, light and easy to cut, are glued in a few hours per room. This guide takes you from cutting the corners to the final paint.

Choosing your coving: polystyrene or polyurethane

Expanded polystyrene coving is economical (from 3 to 8 euros per metre), very light and cut with a knife, but it stays fragile and sensitive to knocks. Polyurethane, denser and more resistant (from 8 to 15 euros per metre), is cut with a saw, does not warp and takes paint perfectly. Choose the width according to the ceiling height: from 6 to 10 cm for 2.40 to 2.60 m, more for high ceilings.

Cutting the corners with a mitre box

The corners of a room are never perfectly square: the safest method is to cut each piece of coving at 45° in a mitre box, paying attention to the orientation of the moulding. For a clean cut in polystyrene, use a well-sharpened knife in several passes; for polyurethane, a backsaw or mitre saw. Always measure against the wall, never by eye.

1. Measure each side of the room and transfer the length onto the coving
2. Position the strip in the mitre box, with the face of the moulding upwards
3. Cut at 45° the two ends that meet in the corner
4. Check the join of the two cuts on the corner before gluing
5. Glue the corner pieces then the strips with the adhesive suited to the support

Gluing to the ceiling, filling and painting

Apply the adhesive to the back of the coving in a zigzag or bead, then press it against the wall and ceiling holding for a few seconds. Polystyrene is fixed with a resin-based adhesive or a mastic-adhesive; polyurethane is glued with a polyurethane or neoprene adhesive. Fill the joints between pieces with filler or a flexible mastic, smoothing with a damp sponge. Once the adhesive is dry (24 hours), apply a primer then an acrylic paint in two coats, preferably before painting the wall and ceiling: polyurethane is painted like a classic moulding, polystyrene requires a solvent-free paint so as not to melt.

Precautions and mistakes to avoid

• Using a solvent or alkyd paint on polystyrene: the material melts
• Cutting the corners without a mitre box: the joins gape visibly
• Gluing on a damp, greasy or dusty ceiling: the coving comes away
• Measuring by eye: a "too short" coving is immediately visible

Fitting ceiling coving gives a room a neat finish and hides the defects of the join between wall and ceiling. With a mitre box, a suitable adhesive and careful filling of the joints, the result is clean and lasting. Allow one day for an average-sized room, and your ceiling will look great.