Decorating a Side-Return Kitchen Extension in London
New plaster drying times, matching existing finishes, colour choices for open-plan kitchen-diners, and how to handle bifold door reveals in a London side-return extension.
The side-return extension challenge
A side-return kitchen extension is one of the most common and transformative renovations in London terrace houses. The narrow strip of land running alongside the ground floor is opened up, glazed over, and merged with the existing kitchen to create a wide, open-plan kitchen-diner. The result is spectacular — but it creates a genuine decorating headache. You now have new plaster walls meeting old walls, new plaster ceilings meeting old ceilings, a fresh concrete or screed floor replacing what was once an exterior wall, and bifold or sliding door reveals that need to be finished to a standard worthy of the glazing they frame.
Getting the decoration right in a side-return extension requires understanding each of these transitions. Here is how we approach them.
Letting new plaster dry properly
New plaster from a side-return extension will typically include a sand-and-cement base coat (brown coat) followed by a finish coat of multi-finish plaster, or in some cases a full hard-wall and skim. Before any paint goes on, the plaster must reach its equilibrium moisture content — and in London's climate, that takes longer than most clients expect.
As a rough guide: allow a minimum of four weeks per 5mm of plaster depth before mist-coating. A freshly skimmed ceiling at 3mm can be mist-coated in three to four weeks. A thick sand-and-cement scratch coat beneath might still be releasing moisture after three months. Use a moisture meter rather than trusting the calendar; readings should be below 12% before you apply a full emulsion coat.
The mist coat itself should be heavily diluted emulsion — roughly 70% paint to 30% clean water — applied in a single thin coat. This seals the plaster surface and lets trapped moisture continue escaping through the paint film rather than blistering beneath it. Never apply undiluted emulsion as the first coat on fresh plaster.
Matching existing finishes
The old kitchen walls will almost certainly have a different surface from the new extension walls. The existing room may have been decorated in a mid-sheen or flat emulsion built up over years; the new plaster has zero paint history. Achieving a visual match across the junction between old and new requires two or three full coats of the same topcoat product on both sides.
Where the old wall meets the new at a corner or doorway opening, this transition will always be visible to some degree. The practical solution is to paint both sides with the same product and accept that a slight tonal variation may persist for the first year while the new plaster continues to dry out and settle. By year two, a single redecoration coat on both sides will equalise everything.
Colour choices for an open-plan kitchen-diner
Natural light is the primary driver of colour choice here. Side-return extensions typically receive good overhead light through a glazed roof but less direct sunlight through the new rear elevation glazing than clients hope. The kitchen end of the extension is often darker than expected.
Mid-tone warm neutrals perform reliably: Farrow & Ball Elephant's Breath, Little Greene Pale Mortlake, Dulux Warm Pewter. These colours hold well in both daylight and artificial light and don't read as grey or cold when the sky is overcast. Cooler greens — Farrow & Ball Mizzle, Little Greene Sage — work well in extensions that genuinely face south or southwest. Avoid very pale cool whites on north-facing or heavily overshadowed extensions; they will look stark and clinical.
The ceiling in a glazed roof extension is often treated with a simple white — we favour Farrow & Ball All White or Little Greene Linen White — which reflects light downward without competing with the view of the sky.
Bifold door reveals
Bifold and sliding door reveals are a finishing detail that many decorators underestimate. The reveal — the inner face of the structural opening — is typically 200 to 400mm deep and painted in a contrasting or complementary finish to the main wall. In most cases we use the same colour as the wall but in a harder finish: an eggshell where the walls are painted in flat emulsion, or a full satinwood where the reveal includes a timber frame or plaster returns that require a wipeable surface.
The steelwork or timber lintel above the opening must be primed with an appropriate metal primer or oil-based primer before any topcoat is applied. New steel lintels are often coated in a rust-inhibiting mill finish from the factory, but this needs a mechanical key (80-grit abrasive) and a coat of Zinsser Bulls Eye 1-2-3 or a suitable metal primer before any water-based topcoat adheres reliably.
Coordinating with the kitchen fit
The ideal sequence is: plaster dry, mist coat, kitchen units installed, then final decoration coats. This avoids the risk of cabinet installation damaging freshly painted walls. Discuss the programme with your kitchen fitter before booking the decorator — the two trades need to dovetail cleanly.
For a professional assessment of your side-return extension decoration, contact our team or request a free quote. We work across Belgravia, Chelsea, Kensington, and throughout SW1, SW3, and SW7.