Decorative Coving Installation Guide

Whether you are opting for a simple concave "C" profile or an ornate Victorian cornice, the quality of the finish depends entirely on the precision of the mitre cuts and the preparation of the surfaces. A well-installed coving can significantly boost a room's perceived value and character.

What Does the Work Involve?

• Surface Preparation: Removing old wallpaper, loose paint, or grease from the wall-to-ceiling junction to ensure a strong adhesive bond.
• Setting Out: Marking "chalk lines" or pencil guides around the room to ensure the coving sits perfectly level, even if the ceiling is slightly uneven.
• Mitring: Precision cutting of internal and external corners using a mitre box or a compound mitre saw.
• Fixing: Applying specialist coving adhesive and securing the lengths in place. Heavier plaster cornicing may require mechanical fixings (screws) into the joists.
• Jointing and Filling: Using fine-surface filler to mask the joins between lengths and the gaps in the corners for a seamless look.
• Sanding and Finishing: Lightly sanding the dried filler before applying a primer and final coats of paint.

Typical Costs

Prices vary based on the material chosen. Lightweight polyurethane or polystyrene is the most affordable, while traditional hand-cast plaster is more expensive due to its weight and the skill required for installation.

Factors affecting the price include the height of the ceilings (requiring scaffolding or high ladders), the number of corners in the room, and whether the walls need significant repair before the coving can be fixed.

How Long Does It Take?

• Standard Square Room: 4–6 hours for installation, plus a return visit for final filling and sanding once the adhesive has set.
• Large Room with Ornate Cornicing: 1–2 days, as heavier plaster requires more time to support and set.
• Full House (3-Bed Semi): 3–5 days depending on the complexity of the profiles chosen.

DIY or Professional?

While lightweight polystyrene coving is a viable DIY weekend project, traditional plaster coving is a different beast entirely. Plaster is heavy, brittle, and notoriously difficult to cut accurately without professional tools. If your mitres are even a few millimetres off, the entire room will look "wonky." For a seamless, high-end finish—especially in period homes—hiring a professional plasterer or coving specialist is highly recommended.

Professional installers use "tacking" techniques to hold heavy plaster in place while it sets, preventing the coving from sagging or falling—a common disaster for DIYers.

Choosing the Right Tradesperson

• Check Specialisms: Not all plasterers enjoy decorative work; look for someone who specifically mentions "coving" or "fibrous plasterwork" in their portfolio.
• Insurance: Ensure they have Public Liability Insurance to cover any accidental damage to your flooring or walls.
• Ask for Photos: Specifically ask to see photos of their internal and external corner mitres—this is where the true skill is visible.
• Questions to Ask:
  • Will you be using mechanical fixings (screws) for plaster coving?
  • Is the disposal of offcuts and old materials included in the quote?
  • Do you provide the materials, or should I purchase them beforehand?

UK Regulations

There are no specific Building Regulations for decorative coving in standard residential homes. However, if you are installing coving in a block of flats or a commercial building, you must ensure the materials meet Part B (Fire Safety) regulations. Most modern plaster and polyurethane coving products are naturally fire-retardant, but always check the manufacturer’s data sheet if you are unsure.

Common Problems

• Cracking at Joins: This usually happens if the building settles or if the wrong adhesive was used. A pro will use "scrim tape" or specialist flexible fillers to prevent this.
• Visible Mitre Lines: If the corners aren't cut perfectly, you'll see a dark line where the two pieces meet. These require expert filling and sanding to disappear.
• Sagging: Often caused by applying too much adhesive or failing to support heavy plaster lengths while they dry.
• Adhesive "Grinning": This occurs when excess adhesive isn't wiped away properly, leaving a visible ridge that prevents paint from sitting flat.

Frequently Asked Questions

Can coving be installed over wallpaper?

It is not recommended. Coving adhesive bonds best to a clean, porous surface like bare plaster or painted masonry. If you install it over wallpaper, the weight of the coving could cause the wallpaper to peel away from the wall, bringing the coving down with it.

What is the difference between coving and cornice?

Generally, "coving" refers to simpler, uniform profiles (like the standard 'C' shape) that are the same distance across the wall as they are across the ceiling. "Cornice" is typically more ornate and often has an asymmetrical profile, extending further across the ceiling than down the wall.

Do I need to paint plaster coving?

Yes. Even though plaster coving is white, it is very porous and will absorb dust and moisture if left unsealed. You should apply a mist coat (watered-down emulsion) or a specialist primer before finishing it with your chosen ceiling or wall paint.

Can coving hide electrical cables?

Some modern polyurethane coving is specifically designed with a hollow "trunking" space behind it to hide LED strips or thin cables. However, traditional plaster coving is usually solid or flush-back, making it unsuitable for hiding wires unless they are chased into the wall first.

How do I choose the right size for my room?

As a rule of thumb, the higher the ceiling, the larger the coving can be. For standard 2.4m UK ceilings, a 70mm to 90mm profile is common. For grand Victorian ceilings (3m+), you can go up to 150mm or larger without the room feeling cramped.