Repairing and Painting Cornices in London Period Homes

A well-maintained cornice is one of the details that separates a properly decorated period room from a merely adequate one. In London's stock of Victorian, Edwardian and Georgian properties, original plaster cornices are common, but they are also routinely damaged, obscured under layers of old paint, or patched in ways that do not match the original profile. Getting the repair and redecoration right requires both the correct materials and a methodical approach.

Understanding What You Are Working With

Before any remedial work begins, it is worth establishing what the cornice is made of and how it is fixed. Most London period cornices fall into one of two categories:

Run-in-place lime plaster cornices. These are formed by running a template (a zinc or timber profile) along a screed of lime plaster while it is still workable. The result is a continuous, seamless cornice with a profile unique to the original craftsman's template. Run cornices were standard in higher-quality Victorian and Edwardian properties. They are typically robust once set but are vulnerable to cracking at the wall-to-ceiling junction where the building moves.

Fibrous plaster sections. From the late Victorian period onwards, prefabricated fibrous plaster sections -- cast in reusable moulds with a hessian scrim reinforcement -- became common. These were fixed to the wall and ceiling with plaster dabs and scrim tape at the joints. They tend to develop gaps at the joints over time, and individual sections can come loose if the plaster dabs fail.

Knowing which type you have determines how you approach both repair and redecoration.

Removing Paint Build-Up

The single most common problem on London period cornices is accumulated paint. Decades of decorating cycles -- particularly where old limewash or distemper layers have been painted over with modern emulsion rather than stripped back -- can add several millimetres of combined paint to the surface. On a cornice with a fine profile, this is catastrophic: the sharply cut egg-and-dart or dentil detail that reads crisply when clean becomes a soft, blobby outline under 5mm of accumulated paint.

The correct approach depends on the type and depth of build-up:

Limewash and distemper layers can often be softened with warm water and a soft brush, then gently scraped with a wooden or plastic tool. Do not use metal scrapers on plaster cornices -- the risk of gouging the profile is too high.
Emulsion layers over distemper are more tenacious because the emulsion has sealed the distemper beneath. A proprietary paint stripper or poultice may be needed, applied carefully and left to dwell. Test on a small section first.
Multiple emulsion layers can sometimes be removed with steam, applied briefly to soften the paint without saturating the plaster. This requires care and experience -- too long with a steam head will cause lath-and-plaster ceilings to sag.

After stripping, allow the cornice to dry fully before proceeding. Fresh plaster will be revealed in places, and this must prime before any decorative coat is applied.

Filling Damaged Sections

Cracks and missing sections in cornices need to be matched to the original profile before repainting.

For hairline and fine cracks at the wall-to-ceiling junction, a flexible decorator's filler or acrylic caulk is appropriate. Do not use rigid plaster-based fillers here, as the movement that caused the crack will simply re-open a rigid fill. Apply the caulk, tool it to a flush and clean profile, and allow it to cure fully before painting.

For larger repairs and missing sections, a two-stage approach works best. First, build up the basic volume of the missing section with a fine casting plaster or a proprietary cornice repair compound. While this is still workable, use the original profile as a guide: a small piece of the original cornice section, or a profile template made from card, allows you to run the repair to the correct shape. Second, once the repair has set, key it lightly with fine sandpaper and apply a skim coat of finish plaster or cornice cement to blend it seamlessly with the surrounding surface.

Matching the exact profile of a Victorian or Edwardian cornice in a repair is a skilled task. It is far better to spend time getting the profile right at the repair stage than to try to disguise a poorly-matched repair with paint.

The Correct Painting Approach

Once the cornice has been repaired and any paint build-up addressed, painting should be done as follows:

Prime new plaster and repairs. Any bare plaster or newly-filled sections must be sealed with a diluted mist coat (typically 80% emulsion to 20% water) before full coats are applied. Skipping this step will result in the final coat flashing -- appearing patchy where the porous repair has absorbed paint at a different rate from the surrounding surface.

Apply two thin coats rather than one thick coat. Thick paint is the enemy of cornice detail. Two thin coats of a quality matt or mid-sheen emulsion will cover without filling the profile. Use a small cutting-in brush to work paint into the recessed elements of the profile, and remove any excess immediately before it dries in the detail.

Avoid rolling. Roller nap deposits paint unevenly on moulded surfaces and leaves a stippled texture that reads as rough when the light catches it. Cornices should always be brushed, with a 25mm or 38mm quality bristle brush for the body and a fine artist's brush for any particularly deep or intricate detail.

Cut a clean line at the wall and ceiling junction. The shadow line where the cornice meets the ceiling plane and the wall plane is what gives a room its visual precision. A badly cut line here makes even a well-repaired cornice look amateur. Use a clean, flexible cutting-in brush and take your time.

When to Call a Specialist

Very badly damaged cornices, or those where large sections are missing or structurally unsound, may require the services of a specialist fibrous plasterer before a decorator can do their work. We work alongside trusted plasterers for exactly these situations, and we can advise during the initial survey whether specialist plastering is needed before decoration begins.

Repairing and Painting Cornices in London Period Homes