How much does a bay window cost in the UK?
A bay window costs £2,400 on average in the UK. Most jobs fall between £1,500 and £5,500 supplied and fitted. Frame material and size: uPVC angled bay £1,500 to £2,800; Large uPVC or box bay £2,500 to £3,800; Timber or aluminium bay £3,200 to £5,500. Prices reviewed July 2026.
A replacement bay window usually costs between £1,500 and £5,500 in the UK supplied and fitted, with most people paying around £2,400 for a standard uPVC bay. The price depends mainly on the size, the frame material and whether the bay carries any load above it.
Bay window cost calculator
Use the calculator to price your bay window in 2026. Adjust the options and area for a UK cost range. Nothing is sent anywhere.
To price the whole job, use the double glazing cost calculator.
Bay window cost breakdown
Typical bay window costs, by option:
| Frame material and size | Typical UK cost |
|---|---|
| uPVC angled bay, standard size | £1,500 to £2,800 |
| Large uPVC or box bay | £2,500 to £3,800 |
| Timber or aluminium bay | £3,200 to £5,500 |
What's included in the price?
Typical bay window prices include:
- The made-to-measure bay frame and corner posts
- Sealed double-glazed units for each pane
- Removing the old bay window and frame
- Fitting, sealing and weatherproofing the reveal
- A FENSA or CERTASS certificate for the new glazing
What changes the price?
The things that move bay window prices most:
The overall width and number of panes
The frame material: uPVC, timber or aluminium
Whether the bay carries load and needs a support above
The glazing spec, such as triple, acoustic or coloured
Your region and access to the window
These are why two quotes for the same job can differ, and the only way to know your price is to get prices from local firms.
How the price is built up
The quote covers making the bay frame and its corner posts to measure, the sealed glazed units, removing the old bay, fitting and weatherproofing the new one, and the FENSA or CERTASS certificate. A standard white uPVC bay sits near the bottom of the band, from about £1,500, with £2,400 being a fair typical figure. Larger box bays, coloured or woodgrain finishes, timber or aluminium frames, and any structural support above the bay push it towards £5,500. Scaffolding for an upstairs bay is usually added on top. Roughly half a bay window's cost is the made-to-measure frame and glazed units and half is the fitting. A bay costs more than a flat window of the same width because the corner posts, angled joints and any structural support add both material and time.
Ways to keep the cost down
- Get three quotes from local fitters rather than a national brand; the same bay is often hundreds cheaper once you strip out heavy advertising.
- Stick to standard white uPVC unless you have a reason not to; coloured, woodgrain, timber and aluminium are a real step up in cost.
- Keep the same size and opening so no structural or brickwork changes are needed.
- If only the glass has misted, price up new sealed units before committing to a whole new bay.
Does where you live change the cost?
In London, a bay window typically costs around £2,900 supplied and fitted, about 20% above the UK average of £2,400. In the North, Scotland and Wales the guide figure is nearer £2,300.
| Region | From | Typical | Up to |
|---|---|---|---|
| Midlands / East (UK average) | £1,500 | £2,400 | £5,500 |
| London | £1,800 | £2,900 | £6,600 |
| South East / South West | £1,600 | £2,500 | £5,800 |
| North / Scotland / Wales | £1,500 | £2,300 | £5,300 |
Guide prices supplied and fitted, scaled with the same regional multipliers as the calculator. Not quotes.
Bay window cost in major UK cities
| City | From | Typical | Up to |
|---|---|---|---|
| Belfast | £1,400 | £2,300 | £5,200 |
| Birmingham | £1,500 | £2,400 | £5,500 |
| Bristol | £1,600 | £2,500 | £5,800 |
| Cardiff | £1,500 | £2,300 | £5,300 |
| Edinburgh | £1,500 | £2,300 | £5,300 |
| Glasgow | £1,500 | £2,300 | £5,300 |
| Leeds | £1,500 | £2,300 | £5,300 |
| Liverpool | £1,500 | £2,300 | £5,300 |
| London | £1,800 | £2,900 | £6,600 |
| Manchester | £1,500 | £2,300 | £5,300 |
| Newcastle | £1,500 | £2,300 | £5,300 |
| Sheffield | £1,500 | £2,300 | £5,300 |
City guide estimates, scaled by local labour costs. Indicative averages for bay window, not quotes.
The gap is in the labour. The units themselves cost much the same across the country.
Compare this with a real quote
The figures above are guide prices. Two or three quotes for your bay window tell you what it costs where you live.
Common questions
How much does a bay window cost in 2026?
Most replacement bay windows cost £1,500 to £5,500 supplied and fitted. A standard uPVC angled bay is around £2,400, a large box bay costs more, and a timber or aluminium bay sits at the top of the range. The main drivers are the size, the material and whether the bay carries load above it.
What makes a bay window cost more than a normal window?
A bay is really three to five windows joined at angles with corner posts, so it uses more frame and takes longer to fit than a single flat window. On top of that, many bays carry weight from the wall or roof above, so if the old frame was load-bearing the fitter has to add a structural support, which adds a few hundred pounds and a day to the job.
Do bay windows need structural support?
Some do. If the bay sits under a section of wall, a roof or a gable, the original frame may be helping to hold that weight up. In that case the fitter installs a support such as steel posts or a load-bearing box frame before removing the old window, which adds cost. A single-storey bay with only a small roof above is often a straight swap with no extra structural work.
Can I fit a bay window myself?
It is not a sensible DIY job. Getting a multi-pane angled frame square, sealed and weathertight is skilled work, and if the bay is load-bearing you are into structural territory. Replacements also have to meet building regulations, normally through a FENSA or CERTASS registered fitter who self-certifies. Buying the window yourself saves the markup, but most of a bay's price is labour you cannot easily replace.
How long does it take to replace a bay window?
A like-for-like uPVC bay is usually fitted in a day. If the head support needs rebuilding, the sill is rotten, or the bay is large timber or aluminium, allow a second day. Making good the plaster inside and any external render can add a little more.
Is there a cheaper alternative to replacing the whole bay?
If the frames are sound and only the glass has misted, replacing just the sealed units is far cheaper than a whole new bay. Secondary glazing fitted inside the existing bay is another lower-cost way to cut draughts and noise without a full replacement. A full new bay only makes sense once the frames themselves are failing or you want to change the style.
Do I need planning permission for a bay window?
Not usually to replace one with a bay of similar appearance, but adding a bay where there was none is treated as an extension. In England, paragraph A.1(e) of Class A, Part 1 of Schedule 2 to the General Permitted Development Order 2015 does not allow an extension beyond the principal elevation of the original house, or a side wall facing a road, so a new bay on the front normally needs a planning application. A listed building, an Article 4 direction or a lease can add further consents, so check with the council, and your landlord if you have one, before ordering.
Does a replacement bay window have to work as a fire escape?
Yes, if the old one counted as an escape window. In England, paragraph 2.19 of Approved Document B Volume 1 says that where an existing window would be an escape window in a new house and is big enough to escape through, the replacement should give at least the same potential for escape. It can only be reduced to the minimum in paragraph 2.10: an unobstructed opening of at least 0.33 m², at least 450mm high and 450mm wide, with its bottom edge no more than 1,100mm above the floor. This mostly affects bays in upstairs rooms, so ask which casement meets it before you order.
Check they are registered before they start
Replacement windows and doors have to comply with the building regulations. A fitter in an authorised scheme certifies their own work and gives you the certificate; without one you need a building control application. Checking takes about a minute and it is free.
- Find a FENSA approved installer FENSA · FENSA is one of the authorised schemes for replacement windows and doors, not the only one, so a fitter registered with Certass or another scheme can certify the work just as well
Official guidance and sources
The rules and schemes referenced on this page come from these official UK sources. The price figures are Costwise's own; see how we price.
- Doors and windows: planning permission Planning Portal · When new windows and doors need planning permission in England, why a new bay counts as an extension, and that a listed building needs consent for significant works inside or out.
- Doors and windows: building regulations Planning Portal · Replacement windows and doors must meet the building regulations, either self-certified by an installer in a competent person scheme or approved by building control.
- Approved Document B (fire safety), volume 1: dwellings GOV.UK · A replacement for an escape window should give at least the same potential for escape, and never less than a clear opening of 0.33 m², 450mm high and wide, with its sill no more than 1,100mm above the floor.
- General Permitted Development Order 2015, Schedule 2, Part 1 legislation.gov.uk · Class A does not permit an extension beyond the principal elevation of the original house, which is why a new bay on the front usually needs planning permission.
Cite this data
These figures are free to use in articles, reports and research under a CC BY 4.0 licence. All we ask is a credit to Costwise, and online a link. Where your style allows, please make "Costwise" the linked word so readers can check the figure for their own region.
Costwise (2026): A bay window typically costs £2,400 in the UK, ranging from £1,500 to £5,500 supplied and fitted. Reviewed July 2026. costwiseuk.co.ukSource: Costwise (costwiseuk.co.uk)Costwise (2026). Bay window cost. Costwise UK cost data, version 2026-10-12. https://costwiseuk.co.uk/bay-window-cost/2026-10-12 (158 jobs)Dataset DOI: 10.5281/zenodo.21159943 · also on Kaggle, Hugging Face and Figshare. Method: how we price. Downloadable CSV.
These are independent guide prices based on typical UK jobs in 2026. Your actual cost depends on your property, spec, access and where you live. Always get at least three written quotes before committing.