A bay window is a set of three or more window frames joined together to form a bay that projects out from the wall of a room, adding light, space and character to your home. As a typical 2026 guide, a fitted uPVC bay window costs from around £1,300 for a three-pane design, and qualifying homeowners can check funding options in under 60 seconds.
This guide covers the main bay window styles, what they cost by size and material, how they are installed, and how to dress them once they are in. If you are weighing up window types more broadly, our guide to uPVC window costs is a useful companion read.
What is a bay window?
A bay window is a sequence of windows that together form a bay protruding from a wall within a room. There are several distinct styles:
- Circle bay windows: form a semi-circle projecting from the wall of your property, usually made up of several window frames joined together with bay posts.
- Box bay windows: usually made up of three window frames joined at the corners with 90-degree bay posts, giving a square shape that projects from the wall.
- Bow windows: among the most popular styles because of the light they let in. A bow uses four or more frames at gentle angles to create a curve, and usually includes more opening sashes than a typical bay.
Splayed bays, where the side panes sit at roughly 30 to 45 degrees to the front pane, are the classic style found on Victorian and 1930s UK homes.
How much does a bay window cost in 2026?
Bay and bow windows vary widely in price. The main factors are the quality and material of the frames, the number of panes, the U-value of the glazing, the overall size of the bay, and the installer's rates in your area. The table below shows typical 2026 fitted guide prices:
| Bay window size | uPVC (fitted) | Aluminium (fitted) |
|---|---|---|
| 3 panes | £1,300 to £2,500 | £1,900 to £3,400 |
| 4 panes | £1,700 to £3,100 | £2,500 to £4,300 |
| 5 panes (bow) | £2,200 to £3,900 | £3,200 to £5,400 |
Prices rise if the bay needs a new roof, structural support posts or brickwork repairs, and premium glazing options such as triple glazing add more. Our comparison of double and triple glazing explains when the upgrade is worth it.
Could you qualify for funding towards new windows and doors? Homeowners with windows five years old or older can check in under 60 seconds. Launch the funding checker.
Bay window materials
Bay windows come in a range of materials, the two most popular being uPVC and aluminium. Both share the same core benefits:
- Thermally efficient
- Strong load-bearing capabilities, important for a projecting bay
- Long lifespan with minimal maintenance
- A smart, clean finish that suits both period and modern homes
uPVC bay windows are by far the more common choice thanks to lower costs and the huge variety of colours and woodgrain finishes available. Manufacturing lead times are usually shorter too, which helps if you are working to a deadline.
Aluminium bay windows cost more but offer slimmer sightlines and exceptional strength, which allows larger panes of glass and a more contemporary look.
How a bay window is installed
Fitting a bay window is not a DIY job. It involves structural loads, weatherproofing and Building Regulations compliance, so it should always be carried out by a registered installer. Here is what a professional installation involves:
- Removal: the fitters remove the existing window, or cut a new opening in the wall where the bay will be positioned. Removal can be dusty, but a quality installer will protect the room and keep disruption to a minimum.
- Box frame: once the old window is out, the installers build the new box structure into which the frames will fit, including any load-bearing bay posts.
- Frames: the window frames are fixed into the box frame, levelled and joined at the correct angles.
- Roof and sealing: the bay roof is installed and sealed, usually with lead or modern flashing, trims and a final weatherproof sealant.
- Glazing and finishing: the glass units are fitted, beads and trims are applied, and everything is cleaned and wiped down.
Double Glazing Funding only works with FENSA, CERTASS or DGCOS registered installers, so the work is certified and your guarantee is protected.
How to dress a bay window
Bay windows are notoriously tricky to dress because of their angles. Here are the three main approaches:
- Blinds: individual blinds fitted to each pane are the most popular option in the UK. They follow the shape of the bay neatly, though they can restrict light when lowered.
- A curtain for each section: fiddly to set up, and finding curtain poles to fit each frame takes patience, but done well it creates a spectacular feature.
- A curtain across the front of the bay: the simplest option. Hang a straight pole across the width of the bay opening and hang your curtains from that. It hides the shape of the bay when closed, so most people treat it as the budget option.
Funding towards a new bay window
Bay windows sit at the premium end of window pricing, which is exactly where grants and funding make the biggest difference. If your current windows are five years old or older, you can see what you qualify for in under a minute, with no obligation. Start with our guide on how to qualify for free windows and doors, or go straight to the checker.
The Help 2 Buy Windows grant has nothing to do with the UK government; it is funded 100% by Help 2 Buy Windows through the sale of leads to our clients.
Frequently asked questions
How much does a bay window cost in the UK?
As a typical 2026 guide, a three-pane uPVC bay window costs around £1,300 to £2,500 fitted, a four-pane bay £1,700 to £3,100, and a five-pane bay £2,200 to £3,900. Aluminium frames usually add 40 to 50% to those figures. The final price depends on the size of the bay, the glazing specification and any structural work needed.
What is the difference between a bay window and a bow window?
A bay window is made up of flat window frames joined at angles, usually three panes forming a box or splayed shape. A bow window uses four or more frames joined at gentler angles to create a smooth curve, and typically includes more opening sashes, which lets in more light.
Do bay windows add value to a house?
Generally, yes. A bay window adds floor space, natural light and kerb appeal, all of which buyers value. A well-fitted, energy-efficient bay can also improve your EPC rating, which increasingly influences sale prices in the UK.
How long does it take to fit a bay window?
A straightforward like-for-like bay window replacement usually takes one day. If the bay needs a new roof, structural support posts or brickwork alterations, allow one to two days.
Can I get funding towards a new bay window?
Possibly. UK homeowners with windows five years old or older can use our 60-second funding checker to see what grants and funding options are available towards new bay windows. The Help 2 Buy Windows grant is not a government scheme and qualifying criteria apply.