Coving & Cornice Restoration in London: Repairing and Painting Period Plasterwork

Coving & Cornice Restoration in London

London's period properties are defined as much by their plasterwork as by any other architectural element. Walk into the drawing room of a Georgian townhouse in Belgravia, a Victorian reception room in South Kensington, or an Edwardian dining room in Hampstead, and the cornice above the picture rail is one of the first things your eye registers — an elaborate continuous moulding where wall meets ceiling, often incorporating egg-and-dart, dentil courses, leaf scrollwork, or other classical ornament.

These cornices are remarkable survivors. The best of them are nearly two centuries old, cast or run in lime-based plaster by craftsmen whose skills have largely disappeared. They are also vulnerable: structural movement, moisture ingress, previous botched repairs, and the accumulated weight of accumulated paint layers all take their toll. And when it comes to repainting, the cornice is the element most commonly damaged by careless work.

This guide covers the restoration and repainting of period cornices in London properties — from assessing the condition of existing plasterwork to commissioning the right repairs and applying paint in a way that enhances rather than obscures the moulding.

Understanding the Cornice

Historical Background

The classical cornice — derived from the horizontal band at the top of a column's entablature — has been a feature of English interior architecture since the early seventeenth century. By the Georgian period, it was ubiquitous in polite domestic architecture, and manufacturers of pre-cast plaster mouldings supplied standard profiles that were used in thousands of London houses.

The Victorians elaborated further, adding more complex profiles and incorporating naturalistic ornament — acanthus leaves, flowers, ribbons — alongside the classical vocabulary. Edwardian cornices tend to be lighter in character, often combining classical mouldings with Arts and Crafts elements.

Construction: Run vs Cast

Period cornices in London were made by one of two methods, or a combination of both.

Run-in-place cornices were created by a craftsman drawing a shaped metal template (a profile gauge) along a chalk line on the wall and ceiling, building up the moulding in successive layers of lime plaster. The plasterer would return multiple times as each coat dried, gradually building up the full profile. Run cornices have a characteristic organic quality — no two sections are quite identical — and their profiles often have subtle variations that are the mark of handcraft.

Cast cornices were produced in moulds, typically made of gelatine or plaster, from a master moulding. Individual cast sections were fixed to the wall and ceiling with plaster dabs, and the joints between sections were made good with run plaster. Cast sections allowed for the inclusion of finer detail — the sharper arrises and deeper undercutting of egg-and-dart or dentil moulding — than was easily achievable by running alone.

Many London cornices use both techniques: the basic profile run in place, with individual repeating ornamental elements cast separately and inserted at intervals. Restoring a damaged section of this type requires identifying both the run profile and the cast elements.

Assessing the Condition of Your Cornice

Before any repair or repainting work begins, a careful condition assessment is essential. This involves both visual inspection and physical testing.

Signs of Structural Weakness

Hollow sections are the most serious concern. Tapping the cornice gently with a knuckle and listening for a hollow sound indicates that the plaster has separated from its backing — either from the ceiling laths (in older properties) or from the structural plaster behind. Hollow sections must be repaired before repainting; painting over loose plaster simply seals in a problem that will eventually result in the cornice falling.

In extreme cases, entire sections of cornice in London properties have fallen away, sometimes without warning, presenting a safety hazard. Any cornice showing significant hollowing should be assessed by a specialist plasterer before other works proceed.

Cracks ranging from fine surface crazes to large structural cracks through the depth of the moulding indicate movement. Fine crazes can often be filled and painted. Wide or active cracks (where the two sides of the crack are at different levels) require investigation of the cause before treatment.

Previous repairs that have been carried out in inappropriate materials — particularly gypsum filler or cementitious materials on what was originally a lime plaster cornice — often fail over time and may need to be removed before new repairs can be carried out effectively.

Paint Build-Up

One of the most common problems on London period cornices is the progressive obliteration of fine detail by accumulated paint layers. A moulding that was originally crisp and sharp, with clearly defined arrises, shadow lines, and individual elements, can be almost unreadable after a century of overpainting with no preparation in between.

The issue is not simply aesthetic. Thick paint build-up in the deeper parts of a moulding is adhesion failure waiting to happen: the accumulated layers eventually reach a weight and thickness where they peel away from the substrate, sometimes taking chunks of the original plaster with them.

The options for dealing with excessive paint build-up are:

Steam stripping, which softens accumulated paint for removal with a scraper. Effective but time-consuming and requires great care to avoid damaging the plaster beneath.
Chemical stripping, using a paste stripper that softens paint for removal. Slower and gentler than steam, but potentially leaves residue that affects the adhesion of new coats.
Accept and minimise the build-up, applying thin coats and using diluted paint in deep grooves to avoid adding further to the problem.

For highly significant period cornices, we often recommend involving a conservation plasterer in the assessment before deciding on approach.

Repair Methods

Lime Plaster vs Gypsum: Why It Matters

The vast majority of original cornices in London Victorian and Georgian properties are lime-based plaster — either traditional lime putty plaster or hydraulic lime mixes. Lime plaster is relatively flexible, breathable, and compatible with the movement behaviour of the masonry construction it adorns.

Modern gypsum plaster (the standard repair material used by most general plasterers) is harder, more brittle, and less permeable than lime. Applying gypsum repairs to lime plaster can cause problems: the differential movement between lime and gypsum can cause the repair to crack at its edges, and if moisture is present in the wall or ceiling structure, the gypsum can actually pull moisture from the surrounding lime, accelerating its deterioration.

For repairs to original lime plaster cornices in period London properties, a lime-compatible repair material should always be used. This typically means:

Hot-mix lime putty plaster for substantial repairs carried out in multiple coats
Hydraulic lime-based repair mortar for smaller patch repairs where a quicker-setting material is needed
Pre-mixed lime-based restoration plasters (such as those supplied by Leslie Taylor or similar heritage suppliers) for smaller repairs

This is not an area where standard decorating supplies are adequate. A contractor without experience of lime plasterwork should not be attempting these repairs.

Running New Sections

Where a section of run cornice has been lost — perhaps following a water leak, or where a previous repair has failed — a new section can be run in place by a skilled plasterer using the same technique as the original craftsmen. This requires:

Profiling the existing moulding to create a matching gauge or template. This may involve taking measurements and making a physical template, or (for more complex profiles) using a 3D scanner.
Setting up the screed — the guide rails that the template runs along to create the moulding profile.
Running the new section in lime plaster, in multiple coats, matching the profile precisely to the undamaged sections on either side.

Running a new cornice section is time-consuming skilled work. In London, there is a small number of conservation plasterers who specialise in this type of work, and for significant repairs to important period properties, we always recommend bringing them in rather than attempting to patch with filler.

Cast Replacement Sections

For cast ornamental elements that have been lost or damaged — individual egg-and-dart motifs, dentil blocks, acanthus leaf details — new casts can be made from surviving examples using the traditional approach of making a mould from an intact section and casting new elements to fill gaps.

This process requires a surviving intact element from which to make the mould. If no intact example survives, it may be possible to identify the original moulding profile from catalogue records of Victorian plasterwork suppliers, some of which have been preserved in archives.

Painting After Restoration

Allow Adequate Drying Time

New lime plaster repairs must be allowed to cure thoroughly before painting. Lime plaster dries slowly — new patches may take four to eight weeks to cure fully depending on their depth, the ambient temperature, and ventilation. Painting over fresh lime plaster that has not cured will trap moisture, interfere with the carbonation process that gives lime plaster its strength, and almost certainly result in paint failure.

We always advise clients to schedule cornice repairs well in advance of any decorating programme to allow adequate drying time. Where repairs and decoration are being carried out at the same time, the decoration sequence should leave the repaired cornice as the last item to be painted.

Paint Selection

For lime plaster cornices, breathable paint systems are preferred. Limewash is the most historically authentic choice and can give beautiful results, but it requires more frequent reapplication than modern paints and is unsuitable for highly detailed mouldings where the milky finish can obscure fine detail.

Clay-based emulsions (such as Earthborn Claypaint) are another breathable option that works well on lime substrates and produces a beautifully flat, chalky surface.

Standard modern emulsion is acceptable for cornices that are not in contact with active moisture and where the lime plaster is well-cured and in good condition. We use either Farrow & Ball Estate Emulsion or Little Greene Intelligent Matt for most of our cornice work, diluting the first coat slightly to help it penetrate the plaster surface.

Application Technique

The golden rule for painting detailed cornices is: thin coats, applied with care, working into every groove. Never apply paint thickly in the hope of covering imperfections quickly — this simply adds to the paint build-up problem and risks obscuring the crisp lines that make period plasterwork so appealing.

We use small, good-quality bristle brushes for detailed cornice work, working paint into the deepest grooves first and then picking out the raised elements with a cleaner brush. Each coat should be allowed to dry thoroughly before the next is applied, and light sanding between coats maintains surface quality.

When to Call a Conservation Plasterer vs a Decorator

A decorator — however skilled — is not a plasterer. There are clear limits to what decorating work should encompass when it comes to period cornices:

A decorator can: fill minor cracks and surface defects, apply paint carefully to avoid obscuring detail, and advise on paint selection.

A conservation plasterer is needed for: running new sections of cornice, casting replacement ornamental elements, re-fixing loose or hollow sections, and any structural repair work.

We maintain working relationships with several trusted conservation plasterers in London and can coordinate their involvement in your project where necessary. If you are planning any work to a significant period cornice, contact us for an initial assessment before committing to a programme of works.