Domakihub How to Fit Ceiling Cornice: A Room-by-Room Guide
Cut, glue, and finish plaster or polystyrene cornice like a trades professional.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
Ceiling cornice (also called coving) is the moulded strip that bridges the wall-to-ceiling joint, hides shrinkage cracks, and gives a room a finished, professional look. The video above walks through measuring, mitre-cutting, and gluing cornice in a domestic setting; this guide expands on every stage so you can plan the job confidently — whether you are refreshing an Athenian apartment, a Crete holiday villa, or a boutique hotel room. In Greece, fitting decorative cornice is pure DIY territory and needs no permit; structural or damp-related ceiling work, however, should always be referred to a licensed builder.
Choosing the Right Cornice for the Space
Plaster cornice is the traditional choice for Greek homes: it is dense, takes paint well, and can be scribed to match ornate existing profiles. Modern polystyrene and polyurethane cornice cost less and weigh almost nothing — ideal for ceilings with limited fixing depth or for holiday rental rooms where fast turnover matters. Profile sizes range from 55 mm to 200 mm; a larger room generally suits a deeper profile, while a narrow corridor or low-ceiling space calls for something modest.
In older buildings with lime-rendered ceilings — common in island properties and pre-1980 mainland apartments — test the wall and ceiling surfaces for soundness before committing to adhesive-only fixing. Friable or flaking plaster should be stabilised with a diluted PVA bonding agent and allowed to cure overnight.
Tools and Materials You Will Need
Core kit: a mitre box or powered mitre saw (set to 45° for internal and external corners), a wide filling knife, a caulking gun, cornice adhesive (gypsum-based for plaster cornice; solvent-free grab adhesive for polystyrene), fine-grit sandpaper, a damp sponge, decorator's caulk, and a straight edge or chalk line. You will also need a pencil, tape measure, and a spirit level for longer runs. A step platform rather than a ladder gives you both hands free and is strongly recommended.
Optional but useful: a profile gauge to copy an existing ornate cornice when marrying new sections into old, and a cordless drill with a countersink bit if you intend to mechanically fix heavy plaster pieces (200 mm and above) in addition to adhesive.
How to Fit Ceiling Cornice: Step by Step
- 1
Mark guide lines on the wall and ceiling
Hold a sample length of cornice in position in the corner and mark the bottom edge on the wall and the top edge on the ceiling with a pencil. Snap a chalk line along each mark to give yourself a continuous guide the full perimeter of the room. These lines control the alignment of every length and are especially important on walls that are not perfectly plumb.
- 2
Cut the mitres
Internal corners (the ones that go into the room) require two pieces each cut to 45° in opposite directions. External corners (around a chimney breast or column, for example) are the mirror image. Use a mitre box for polystyrene cornice and a mitre saw for plaster. Always cut slightly long and test-fit dry before applying adhesive — you can trim back, but you cannot add length. Mark the face side with a pencil arrow so you do not flip a piece when gluing.
- 3
Apply adhesive and bed the cornice
For plaster cornice, dampen both the back of the moulding and the wall/ceiling surfaces with a wet brush so the gypsum adhesive does not dry out before it bonds. Apply adhesive in a continuous bead along both flanges (top and bottom edges), then press the cornice firmly into position along your chalk lines. Scrape away any squeeze-out immediately with a damp filling knife. Use temporary nails or masking-tape tabs to support each length while the adhesive sets — typically 20 to 40 minutes for gypsum, longer in humid coastal conditions.
- 4
Fill corner joints and butt joints
Once adhesive has set, fill the mitre joints and any butt joints (straight joins along a run) with cornice adhesive or a flexible interior filler. Feather the filler flush with a damp filling knife, working it into the joint without leaving ridges. Allow to dry fully — at least two hours in summer Greek conditions — then lightly sand with 120-grit paper. Wipe away dust with a damp cloth before priming.
- 5
Prime, caulk the edges, and paint
Seal bare plaster cornice with a diluted mist coat of white emulsion (3 parts paint to 1 part water) or a dedicated plaster primer; polystyrene requires a water-based primer only — solvent-based products melt expanded polystyrene. Once primed, run a thin bead of flexible decorator's caulk along the top and bottom edges of the cornice where it meets the ceiling and wall, smooth it with a wetted finger, and allow to dry. Then apply your finish coat. Two thin coats of ceiling-grade emulsion give a cleaner result than one thick coat.
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FAQ
- Can I fit ceiling cornice over existing tiles or textured paint?
- Cornice adhesive needs a clean, sound surface to grip. Gloss paint and ceramic tiles must be keyed with coarse sandpaper or a scoring tool before bonding. Heavy textured finishes (stipple, sand-finish render) should be scraped back to a flat surface along your guide lines, or the cornice will rock and the bond will fail at the high spots.
- How do I cope with an out-of-square corner — very common in older Greek properties?
- True 90-degree corners are rare in older buildings. The fix is to scribe the mitre: cut both pieces at 45°, test-fit them, and then use a coping saw or oscillating multi-tool to trim the back piece until it follows the exact profile of the front piece. Alternatively, fill the gap with cornice adhesive and smooth it to match the profile before it sets. A flexible caulk at the painted stage will absorb any residual movement.
- When should I call a professional plasterer instead of doing this myself?
- Call a licensed plasterer if: the existing ceiling shows signs of water damage, sagging, or delamination (these point to a leak or structural issue that must be fixed before any finishing work); you need to match a highly ornate historical profile that requires casting a new mould; or the ceiling is unusually high (above 4 m) and requires scaffolding. For straightforward decorative cornice in standard residential or hospitality rooms, the job is well within confident DIY scope.