How Much Do Bay Windows Cost in 2026?
Check what new windows should cost, then get free quotes from local installers.
Your Estimate
£12,500 – £30,000- Supply only, you arrange fitting−£10,500
- Upgrade to triple glazing+£3,625
- Switch to aluminium frames+£7,450
- Switch to timber frames+£19,150
Now find out what yours actually costs
Installers covering your postcode will quote for your real windows, so you have something to check the benchmark against.
Get quotes for my 10 windowsPrices are estimates based on UK market averages for 2026. Actual costs vary by supplier, location and property. Always get 3 quotes before committing.
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. The number of panels is what separates a three-panel box bay from a wider run, and it moves the final price more than the glass does. A bay is usually the largest opening in the room it sits in, which is why homeowners rarely replace one with something smaller. The calculator above defaults to the Bay style, so count each bay as one window rather than as a standard window per pane. If the frontage curves smoothly rather than turning sharp corners, you have a bow window instead, priced by section count. A uPVC bay costs £1,250 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 how much 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 | £1,250–£3,000 | £1,690–£4,050 | £2,380–£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.
What replacing an existing bay window costs
Replacing a bay you already have costs the same £1,250 to £3,000 per bay in uPVC as a new one, because the price is driven by the unit and the fitting rather than by what was there before. Two things move it. The first is what the old bay was carrying: if the frames are structural and the bay supports masonry above, the installer fits a load-bearing beam while the old unit is out, and that is the single largest variable on a bay replacement. The second is what turns up once the frames are removed, typically rot in the sill or a lintel that was never right, neither of which is visible from inside. That is why a survey figure and this estimate can differ on a bay more than on any other style, and why the range above is wide. If only the glass has failed rather than the frames, the repair cost calculator weighs a reseal against a full replacement.
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.
Double Glazing Cost Calculator Team
Frequently asked questions
A uPVC bay window costs £1,250 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 £1,250 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.