Types of Coving and Cornice in London Properties: Identifying and Painting Each Correctly

Why It Matters What Your Coving Is Made Of

Coving and cornice in London properties spans almost every period and every material: run-in-place lime plaster from the 1800s, fibrous plaster cast in sections from the 1870s to the 1950s, modern polystyrene profiles installed from the 1970s onwards, and more recently glass-reinforced polymer (GRP) profiles that attempt to replicate period originals. Each material has different preparation requirements, different failure modes, and different appropriate painting approaches.

Getting this wrong is not a trivial matter. Coving that has been incorrectly prepared — painted over with the wrong primer, overfilled, or sealed with the wrong products — develops problems that can be difficult and expensive to reverse. And in a period property, damaged or badly painted cornicing is one of the most immediately visible signs of poor-quality decoration.

Run-In-Place Lime Plaster Cornice

The oldest cornice type found in London properties is run-in-place lime plaster — literally formed in position on the wall by drawing a profiled zinc or aluminium template along a screed to create the moulding. This method dates back to the seventeenth century and was the standard technique for forming cornices in Georgian and early Victorian London.

How to identify it: Run-in-place cornices have a slightly organic quality — minor variations in the profile across their length, occasional small repairs visible as slight colour differences in unpainted sections, and a chalky, matte surface on old painted examples. The return at internal corners is typically formed by hand and may not be perfectly crisp. The profile is often complex: multiple coves, fillets, and fascias rather than a single curved section.

Preparation: Never use a cellulose filler directly on lime plaster cornice. The different movement characteristics between modern cellulose fillers and historic lime plasterwork will cause the filler to crack at the join within one to two heating cycles. Use a lime putty filler (Limelite or similar) for any repairs, or a flexible acrylic stopper applied in thin layers for hairline cracks. If the cornice surface is powdery or chalky — which lime plaster often is under layers of old paint — apply a stabilising primer such as Zinsser Gardz or a diluted PVA (1:3 ratio) before any further work.

Painting: Brush-apply rather than roller. A roller used on complex period cornicing will deposit too much paint in the recesses, obscuring detail and building up layers that eventually crack and fall. Use a 2–3 inch cutting brush and work methodically. An oil-based undercoat on lime cornice helps consolidate the surface and provides a stable base for water-based topcoats. Farrow & Ball Estate Emulsion (dead flat) applied with a brush reads beautifully on run-in-place cornicing because the absence of sheen shows the profile in its best light.

Fibrous Plaster Cornice

From the 1870s onward, fibrous plaster — plaster reinforced with hessian scrim rather than lime hair — became the dominant method for producing ornate cornicing in London's wealthier developments. Fibrous plaster cornice was cast in sections in a workshop from an original model and installed in lengths, giving much more consistent profile detail than run-in-place work.

How to identify it: Fibrous plaster cornice is more uniform than run-in-place work. Sections are typically 2–3 metres long with a neat mitred join at the angle where two lengths meet. The profile is sharper and more consistent than lime work, and the material has a slightly brittle quality — it chips rather than crumbling. Fibrous plaster cornice is found in Victorian mansion flats, Edwardian townhouses, and purpose-built flat conversions across London's inner suburbs.

Preparation: Fibrous plaster is broadly compatible with modern acrylic products but benefits from a light key on glossy painted surfaces before repainting. Hairline cracks at section joints are almost universal — these should be raked out slightly, filled with a flexible filler (Toupret Fibacryl or similar), and allowed to cure completely before being rubbed down. The scrim backing behind the plaster can become exposed if sections are damaged; exposed scrim must be consolidated before painting.

Painting: The standard approach is one coat of Dulwich Trade Undercoat or Zinsser Bulls Eye 1-2-3 primer, followed by two topcoats of emulsion or eggshell depending on the surface (wall-type surfaces in emulsion, woodwork-adjacent sections in eggshell if the woodwork is being finished in eggshell). Brush work throughout — keep coats thin on fibrous plaster to preserve the definition of enrichments (dentils, egg-and-dart mouldings, paterae).

Polystyrene Coving

From the 1970s through the 2000s, polystyrene coving was widely installed as a quick and inexpensive substitute for plaster coving. Sold in standard sizes at DIY stores and applied with adhesive, polystyrene coving has a simplified, slightly soft profile compared to period originals.

How to identify it: Polystyrene coving has a slightly springy or flexible quality when pressed. The surface feels smooth but slightly waxy. Profiles are simple — typically a single cove or a basic ogee — and internal mitres are cut from the same material rather than being formed in place. If a length is pulled away from the wall it will flex rather than snap.

Preparation: Polystyrene coving is problematic to paint. The surface is non-porous and many standard paints will not bond to it adequately without a specific primer. More importantly, polystyrene is incompatible with solvent-based products: a solvent-based undercoat or oil-based paint applied directly to polystyrene will dissolve the surface. Apply only water-based products. Use Zinsser Bulls Eye 1-2-3 (water-based) or Dulwich Trade Multi-Surface Primer as a bonding primer. Do not use white spirit or paint thinner to clean polystyrene coving — it will melt it.

Painting: One coat of water-based primer followed by two coats of water-based emulsion. Because polystyrene coving sits flush against the ceiling, keeping an absolutely clean line between the coving and the ceiling emulsion requires careful cutting-in or masking tape. A brush is far preferable to a roller here — roller splatter on polystyrene is difficult to remove without damaging the surface.

Should polystyrene coving be replaced? In a period property that had original plaster cornicing, polystyrene coving is always a compromise. If the original cornice is missing and a polystyrene substitute has been installed, the options are: remove it and reinstate a plaster profile to match the original (the right answer for any property of architectural quality), or accept it and ensure it is painted neatly. Polystyrene coving that is well-painted in a white emulsion and cleanly detailed at ceiling and wall is not offensive; it simply is not the real thing.

GRP (Glass-Reinforced Polymer) Cornice

GRP cornice is a relatively recent development used primarily in higher-quality restoration projects and new luxury developments that want a plaster cornice appearance without the weight and installation complexity of fibrous plaster. GRP sections are lightweight, consistent in profile, and dimensionally stable.

How to identify it: GRP cornice has a slight sheen to the unpainted surface and a hard, glassy quality when tapped. Sections are typically longer than fibrous plaster lengths. The material has no flexibility — it is rigid and will crack rather than bend if forced. Internal and external angles are often supplied as pre-formed components rather than cut mitres.

Preparation: GRP requires a mechanical key before painting — light abrasion with 180-grit sandpaper — because the surface release agent used in manufacture prevents adhesion of paints and primers. After abrading, wipe the surface with a damp cloth to remove dust and apply Zinsser Bulls Eye 1-2-3 or a dedicated GRP primer. Without this preparation, paint will peel.

Painting: As per fibrous plaster once primed: undercoat and two topcoats. GRP holds paint very well once properly prepared and can produce an excellent finish. Because the profile is sharp and consistent, the result of careful brush work on GRP cornice rivals the appearance of the best fibrous plaster.

The Universal Rule: Do Not Fill and Paint

The most common mistake on every type of coving — from lime to GRP — is applying paint as a gap-filling agent. Thick paint built up in the cove detail to cover cracks and imperfections produces a finish that looks initially smooth but cracks within months as the paint film shrinks. Repair first, fill properly, rub down, prime, then paint. The paint should be the finishing coat, not the structural layer.

Need Help With Your Cornicing?

Whether you have original Victorian lime cornicing that needs careful restoration, fibrous plaster that needs matching repairs, or polystyrene coving that needs replacing entirely, we can advise and carry out the work. Contact us here or get a free quote.