What a bay window costs in 2026
A bay window projects outward from the wall in three or more angled panes, creating a recess inside and a defining feature on the front of many Victorian and 1930s homes. It is the most expensive common window style to replace, and the reason is structure, not just glass: the bay carries load, so it needs corner posts, a head and a base, and the wall above has to be supported during the swap. In the calculator above, select the Bay style and count each bay as one window. A uPVC bay costs £1,100 to £3,000 fully fitted in 2026 per bay, with aluminium and timber stepping up from there.
Because a bay is priced as a whole unit, it is easy to misjudge against a flat run of windows. Our master double glazing costs page lists the bay row beside casements and sashes so you can see the gap, and the cost per window guide explains why per-bay and per-window figures are not directly comparable.
| Bay window (per bay) | uPVC | Aluminium | Timber |
|---|---|---|---|
| Per bay, fitted | £1,100–£3,000 | £1,490–£4,050 | £2,090–£5,700 |
Source: DGCC 2026 consensus (uPVC bay, per bay); aluminium +35% and timber +90% as applied across the site. A bay is one structural unit, not a count of panes.
Which frame material suits a bay
uPVC is the most common and best-value choice for a bay, and modern profiles carry the structural load well. Aluminium suits a contemporary rebuild or a large bay where slim sightlines matter, and the aluminium window calculator will price it. On a period property in a conservation area, timber may be required for the front bay; price that in the timber window calculator. If the rest of your home has simpler openings, run those through the casement window calculator so your whole-house total is realistic.
The verdict on bay windows
A bay is a feature worth keeping, but it is the costliest window on the house and the figure depends heavily on the structure behind it. Get the labour and the load support priced clearly, not just the glass.
It depends Bay windows: it depends. Worth restoring as a feature, but always price the structural work, not only the panes.
The mistake people make with a bay is comparing the quote to a normal window and thinking they are being overcharged. They are not. Half the job is propping and supporting the wall above while we take the old bay out. Pay for that to be done properly, because a botched bay swap is the one that causes real trouble later.
Tom Bradley, FENSA-registered installer
Frequently asked questions
A uPVC bay window costs £1,100 to £3,000 fully fitted in 2026, priced per bay rather than per pane. Aluminium runs roughly 30 to 40% higher and timber roughly 60 to 110% higher for the same bay.
A bay projects out from the wall in three or more angled panes, so it needs structural corner posts, a head and base, and far more labour to remove and refit than a flat window. That structure, not just the extra glass, is what drives the price up.
Per bay. The £1,100 to £3,000 range covers the whole bay as one unit (typically three to five panes plus the structural frame), not each individual pane. In the calculator, count each bay as one window.
Usually yes, but the structural load above the bay must be supported during the swap, which is why a bay always costs more in labour. A FENSA-registered installer will assess whether the existing corner posts can be reused or need replacing.