Bay Windows

A bay window projects outward from the wall in three sections: a wider central panel flanked by two return panels on either side. The angle of those return panels determines the shape.

A canted bay has returns at 45 degrees, creating the octagonal projection you’ll recognise on Victorian terraces, Edwardian semis, and stone-built bungalows across Central Scotland.

While a square bay has returns at 90 degrees and suits larger openings, extensions, and contemporary builds.

The outward projection serves a purpose.

It adds space and brings in light from multiple angles to create real depth to the room.

The space below the cill is a perfect spot for a built-in seat or storage, and on period properties a well-fitted bay is one of the strongest features on the front elevation.

You might be wondering what the difference is between bay and bow windows.

After all, both project outward from the wall.

A bay window has three sections with angled corner joints: a central panel and two return panels at defined angles.

A bow window uses four, five, or six equal-width panels in a continuous curve, with no corner joints and a rounded profile.

For most Scottish homes, the existing opening suits one or the other based on what was originally fitted.

Canted bays are standard on traditional terraces and bungalows. While a curved bow suits a rounded reveal.

Here at The Advanced Group, we handle both bay and bow window replacement installation.

Whatever your property requires, we will have the double glazing window solution.

Most replacements involve the canted bay, with its 45-degree return panels.

Square bays project at 90 degrees and suit modern builds and larger extensions.

Within either configuration, the individual panels can be casement, tilt and turn, or fixed.

uPVC casement windows open outward on a side hinge and are the standard choice for bay configurations.

The most common arrangement is two opening side panels with a fixed or casement centre, specified to suit the room’s ventilation needs.

Tilt and turn windows open inward, which is useful on upper floors or anywhere reaching outward isn’t practical.

For ground floor bay windows, this controlled ventilation can offer added security.

Sash windows are available in a bay configuration too.

On period properties where the original style was a sliding sash, uPVC sash panels in the bay keep the character of the elevation while giving you modern double glazed performance.

We specify each panel during the survey based on the opening size, the room’s use, and how the reveal is structured.

Timber bay windows tend to fail at the frame joints and the cill long before the glass goes, especially in Scotland’s wet and windy weather.

Moisture slowly works into the connections between the central and return panels and between the frame and the reveal, and rot follows when the windows are not thoroughly maintained.

This is where uPVC comes in as a modern and low maintenance solution.

There’s no painting, no annual sealing, and no ongoing upkeep.

The colour runs through the material rather than sitting on the surface, so it won’t chip, peel, or fade.

A wipe down is all it needs.

Our double glazed uPVC bay windows achieve an A-rated U-value of 1.4 W/m²K as standard.

We can specify units down to 1.2 W/m²K for better performance, and triple glazed bay windows reach values as low as 0.8 W/m²K.

Every unit is made to the exact dimensions taken during the survey, so the frame fills your reveal without cutting down on site.

Our uPVC contains 80% recycled or renewable material, and we collect your old frames for recycling when they’re removed.

White is the most popular choice, but we offer a full range of colours to suit your property perfectly.

Our RAL colour finishes let you go beyond the standard palette and match your existing joinery.

Dual colour finishes are also available, so the exterior can suit the street elevation while the interior matches the room.

Decorative glazing options include Georgian-style bar detailing, bevelled pane arrangements, and obscure or frosted glass for rooms where privacy matters.

We’ve been fitting windows and doors in Scotland since 1988, and bay window replacement is work our teams do week in, week out across Glasgow, Edinburgh, and the wider Central Belt.

You can visit our Glasgow showroom to see working bay window displays for yourself, try the opening mechanisms, and compare colour finishes before we come to you.

Our Trustpilot rating is 9.6 out of 10 from over 500 verified reviews, and more than half our business comes through customer recommendations.

Every installation is carried out by our own expert team of fitters, not subcontractors, and covered by a 15-year guarantee on frames, glass, hardware, and workmanship.

0% interest-free finance is available on all bay window orders, with repayments spread over up to four years and no deposit required.

Call our Glasgow showroom on 01355 271 223 or our Edinburgh team on 0131 370 0444, or request a quote online and we’ll arrange a visit at a time that suits you.

Our surveyor will measure the opening, check the lintel and reveal, and walk you through the styles, configurations, and glazing options available for your property.

You’ll get a written quote with no obligation to proceed, and the survey is free.

Our showroom is completely open for walk-in visits, with working displays of bay windows, bow windows, colour finishes, and glazing options on site.

For premium windows, quality style, and expert savings on your energy bills, contact our team today!