Painting Bay Windows in London Properties: Inside, Outside and Getting the Details Right

Bay Windows: A London Architectural Staple

Bay windows are one of the defining features of Victorian and Edwardian terraced houses across London — from the shallow square bays of Clapham and Islington to the deep curved bays on the grand streets of Kensington and Holland Park. They add light, space, and enormous visual character to a property, and they're one of the elements that most repays careful painting and maintenance.

Get them wrong and they look scruffy from the street, let in draughts, and deteriorate rapidly. Get them right and they can look spectacular — one of those features that makes a London terrace look properly loved and maintained. Here's our complete guide.

Timber vs uPVC Bay Windows

The first consideration is the material. Most Victorian and Edwardian bay windows were originally timber, and many still are. Some have been replaced with uPVC at various points — often in the 1980s and 1990s — and some have been restored with new timber frames.

Timber bays can be painted with a full range of colours and finishes. They require more maintenance than uPVC — typically a repaint every five to eight years for exterior work, depending on exposure — but they respond to paint in a way that uPVC simply doesn't. A well-painted timber bay window looks architecturally alive. The paint sits in the grain, highlights the mouldings, and weathers in a natural way.

uPVC bays can now be painted using specialist uPVC primers and topcoats — a significant advance over ten years ago when painting uPVC was considered unreliable. The key is correct preparation: the surface must be degreased and keyed properly before priming, and the correct primer is non-negotiable. We use specialist uPVC adhesion primers before applying a quality topcoat. The result is durable if the process is followed correctly, but it's not quite as forgiving as painted timber and needs to be done properly the first time.

Sash Windows in Bays vs Casement Windows

Bay windows in period London properties are often glazed with sash windows — typically in a three-part configuration with a wider central pane flanked by narrower side windows. In some properties the side lights are fixed; in others, all three sections are operable sashes.

Sash windows in a bay require particular care around the meeting rail and the sash tracks. We ensure that sashes remain fully operable after painting — never painted shut — and that the weight channels (where present) are accessible. The internal beading that holds the sash in the frame should be painted but not to the point where it becomes bonded to the frame itself.

Casement windows in bay configurations are more common in Edwardian and inter-war properties. The hinged sash needs to be removed or held open during painting and checked for alignment before being replaced. Hinges should be cleaned or replaced if they're showing corrosion, and the rebate should be sealed properly.

Exterior Bay Window Painting: The Full Programme

Repainting the exterior of a bay window properly is a multi-stage process. Here's our standard programme:

Step 1 — Preparation. Strip any flaking or loose paint using a hot air gun (not a naked flame, which can cause fires in older timber). Sand back all surfaces. Rake out any failed putty. Check the sills for soft timber — probe with a screwdriver to identify any rot.

Step 2 — Repair. Fill any cracks and voids with exterior-grade filler. Repair or replace putty. Treat any soft timber with a penetrating consolidant primer before applying filler. In cases of advanced rot, section repairs in matching timber profile may be needed.

Step 3 — Prime. Apply a quality wood primer to all bare or repaired timber. We typically use an oil-based alkyd primer for best adhesion, particularly on older, absorbent timber.

Step 4 — Undercoat. Apply a full undercoat, taking care to achieve good coverage in all mouldings and recesses.

Step 5 — Topcoat. Apply two topcoats in the chosen finish. For exterior woodwork on London period properties, we generally recommend a quality oil-based eggshell or satin rather than a hard gloss — it's more flexible, handles thermal movement better, and ages more gracefully.

Interior Bay Window Painting

The inside of a bay window is often overlooked in favour of the main room walls, but it has a significant visual impact — it's what you see when you look toward the light. Dirty, patchy, or poorly painted window reveals make a room feel uncared for.

Interior window frames are typically painted in the same eggshell or satin used for all the room's woodwork. The sill, if it's timber, should be painted in a durable eggshell — sills take considerable wear from plants, coffee cups, and general use. A washable eggshell is much more practical than a flat emulsion on a sill.

The internal reveal walls — the box enclosing the bay — are often painted the same colour as the main room walls, but painting them slightly lighter can increase the sense of light coming in from the window. This is a subtle trick but it does make a noticeable difference in north-facing rooms.

Sealing and Draught Proofing

While not strictly a painting task, sealing and draught proofing bay windows is often done at the same time as a repaint, since the scaffolding is up and access is good. We always check the external junction between the bay window frame and the masonry surround — this is where gaps form as the building moves over time, and where water can get in.

Flexible external frame sealant — typically an acrylic-modified silicone that accepts paint — is used to seal any gaps at the frame-to-masonry junction. This should be colour-matched to the frame where possible, or painted over as part of the topcoat programme.

For draught proofing the sash or casement openings themselves, this is best done by a specialist draught-proofing company before the painting programme begins, so that the new seals are then protected by the fresh paint.

Choosing a Colour for Bay Window Frames

The classic choice for London period properties is white or near-white — it reads clearly against brick or stucco, it's historically appropriate, and it works with virtually any main body or front door colour. But there's a strong tradition of painted window frames in contrasting colours too, and this can look excellent on the right property.

If you're considering a coloured frame, think about how it will relate to the front door and any railings. A coherent palette — where frame, door, and railings share a colour family — looks more deliberate and more sophisticated than one where each element has been chosen in isolation.

If you'd like a quote for bay window repainting — whether exterior, interior, or both — we'd be happy to visit and assess the work. Get in touch to arrange a time.