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What a UPVC bay window quote should name
A bay window price is the price of a projecting frame on one named wall, including the corners that carry the masonry above. Compare written quotes for the projecting frame on that wall.
Last reviewed:The projection is the product
A bay sticks out from the wall. It has a front face and two returns, a head, a cill, and a seat or a floor that meets the room. A flat casement quote does not describe that shape. When you ask for a price, name the wall, say whether people sit in the opening, and say whether the roof of the bay is lead, tile, flat roofing or part of a porch. Those choices change the frame, the flashing and the making-good. They are not a style adjective you can leave to the brochure.
The table is a list of lines to demand in writing. VAT registration, when taxable turnover for the last 12 months goes over £90,000, is a tax rule and not a window price [S6].
| Line on the quote | What you are trying to pin down |
|---|---|
| Projection from the face of the wall, and the width of the front | Two bays with the same front width can still differ in depth |
| Each return, and whether the returns are glazed or solid | A solid cheek is a different frame from a glass one |
| Corner posts, named, and who is satisfied they carry the wall | A bay is not only glass [S2] |
| Roof of the bay, flashing, and who makes the junction weathertight | Water at the head is a specification |
| Internal seat, cill and plaster, and whether the boards stay | Making good is often missing from a frame-only price |
| Opening left as it is, or made wider | Wider work is a support question [S2] |
| Waste, including the old frame and any lead | Silence is not a waste price |
| VAT | Included or not. Registration starts when taxable turnover for the last 12 months goes over £90,000 [S6] |
Planning permission treats a new bay as an extension
On the Planning Portal doors and windows page, you will not usually need planning permission for repairs, maintenance and minor improvements such as repainting frames, or for new windows of a similar appearance to those used when the house was built [S1]. The same page says a new bay window will be treated as an extension and may require permission [S1]. That sentence is the reason a bay job should say "new" or "replacement" in the first line. Do not let a fitter's brochure collapse the two.
Upper-floor side windows have a separate rule: obscure glazing and non-opening, or the opening part more than 1.7 metres above the floor [S1]. A ground-floor bay on a front wall is not that side-window case, but a bay can still be caught by a listed building, a conservation area, an Article 4 direction or the lease [S1]. Ask the local planning authority if any of those apply to the house [S1]. The planning authority for that house decides, including on a street in Cheshire.
Corner posts are a structural line, not a trim
Lancaster City Council's leaflet on replacement windows to dwellings, issued on 21 January 2013, says that where windows are to be wider replacements, or where a bay is involved, the surveyor must be satisfied about the support above the window and about the bay corner posts [S2]. It also says older timber frames sometimes carried load without a separate lintel, so the choice is to install a lintel or to reinforce the new frame [S2]. The leaflet says a competent-person route does not remove a building regulations application where the opening is made wider and a new support lintel is installed [S2].
Use that as a warning from another council. It is not a Cheshire East policy and it is not a price. Do not copy the leaflet's 2013 heat-loss numbers onto a quote. They are not repeated here. Photograph the corners from inside and outside, standing on the floor, and ask each fitter whether the posts stay, are renewed, or are hidden behind new cladding. A quote that says only "UPVC bay, supply and fit" has not answered the question the leaflet raises.
The glazing rules, and the number to ask for
The GOV.UK booklet on building work, replacements and repairs was updated on 3 November 2014 and applies to England [S3]. Replacement of window units is an example of work to tell a building control body about unless a competent person scheme installer certifies it [S3]. The lists are examples, not a full catalogue [S3]. If you are in doubt, contact a building control body before work starts [S3]. You should receive a certificate within 30 days of completion, and the booklet tells you to contact the scheme if you do not [S3]. FENSA is named for replacement windows and doors [S3].
The Planning Portal building regulations page for doors and windows says that since 1 April 2002 the rules have applied to replacement glazing, covering heat loss, safety, air supply, means of escape and ventilation, and that an external window is a controlled fitting [S4]. The U-value must not be exceeded. The portal points to Approved Document L for the maximum [S4]. A figure copied from memory would be a guess. Ask the fitter to write the glass specification they will actually order, and to say which document they are meeting.
GOV.UK: building regulations approval. QuoteZila is not affiliated with this organisation.
How to compare two bay quotes
Citizens Advice describes a quote as a fixed, agreed price and an estimate as a rough guess you should not treat as a promise [S5]. Do not rely on a verbal figure [S5]. Try to get written quotes from at least three traders [S5]. Be wary of a trader who will not put it in writing, and of a price far below the others, because the work may not be the same [S5]. A useful quote shows a fixed total, a breakdown, how long the price stays open, and whether VAT is included [S5].
For the deposit, the same page says avoid one where you can. If you cannot, do not agree to more than 25%, take a receipt, and ask about deposit protection or an escrow arrangement if the firm fails [S5]. Ask to see insurance and check it lasts until the bay is finished [S5]. Sometimes an insurance-backed guarantee is offered with replacement windows. Read what it covers before you pay extra for it [S5].
A practical comparison is to put both quotes on the same rows as the table above. If one price includes the bay roof and the other stops at the frame, the cheaper line is not the same job. If one includes building control and the other assumes a scheme certificate, ask which route you are on before you accept.
A bay in Cheshire is still your wall
QuoteZila is new and is starting in Cheshire, beginning with Crewe, Nantwich and Sandbach. Anyone in the UK can still post a job or register a business [QZ5]. What matters is the projection, the posts and the council that covers that house. Replies depend on who has joined [QZ5].
Honest status: QuoteZila is new. We're starting in Cheshire, beginning with Crewe, Nantwich and Sandbach, and growing area by area. Anyone in the UK can still post a job or register a business. How fast you get quotes depends on how many local businesses have joined near you. Businesses can register and receive jobs straight away. We don't check insurance, qualifications or registrations, so please check these yourself before you hire.
Up to five matched local businesses can send quotes [QZ2]. QuoteZila is free for customers and local businesses [QZ1].
Posting a job is not open yet
Trade pages for this work include glaziers, builders and joiners. Other guides to reading a written price are fencing cost, driveway cost and locksmith cost.
This page is general information, not professional or legal advice. QuoteZila does not check Gas Safe, WaterSafe, NFRC, NICEIC or other registrations against the register on your behalf: look them up yourself.
Measure the projection from the face of the wall, not only the width of the glass you can see from the street. Ask the quote to name the corner posts, the returns, and whether those returns are glazed or solid. Say if the opening stays the same size. A frame-only price that is silent on the bay roof, the flashing and the internal seat is not finished. Ask who makes the junction weathertight, and who takes the old frame away. Put the same measurements in front of each firm so the replies describe one bay.
Jobs you might post
These are examples, not taken from real job posts.
- "Front bay in Crewe, already there, three faces of glass. I want the projection measured, the corner posts named, and a statement on whether the opening stays the same width."
- "Nantwich side wall. There is no bay now. Please separate a new projecting bay from a flat window, and say you will ask the planning authority before you order a frame."
- "Sandbach. The bay roof leaks at the lead. I want the roof and the frame priced as two lines, and I will say if the posts look soft."
Questions about bay quotes
Is a new bay the same as a replacement window?
Not in planning terms. The Planning Portal says a new bay window will be treated as an extension and may require permission, which is a different case from repairs or from new windows of a similar appearance. A replacement of an existing bay is a different description again. Write on the job whether the bay is already there. A quote that assumes a flat wall is not a quote for a projecting one.
Who should be satisfied about the corner posts?
Lancaster City Council's building control note of 21 January 2013 says that if the new windows are wider, or the job is a bay, the surveyor needs to be satisfied about support above the window and about the bay corner posts. That leaflet is Lancashire guidance, not a ruling for Cheshire East or Cheshire West and Chester. Ask the council that covers the house, and ask the fitter to name the posts as a line on the quote.
Do replacement bays still meet building regulations?
Replacement of window units is an example in the GOV.UK booklet of work to tell a building control body about, unless a competent person scheme installer certifies it. The Planning Portal says an external window is a controlled fitting and that replacement glazing has been covered since 1 April 2002. FENSA is one scheme the booklet names for replacement windows. Ask the fitter to write the U-value they will order, from Approved Document L.
Should I pay a deposit for a bay?
Citizens Advice says that if a deposit cannot be avoided, do not agree to more than 25%, get a receipt, and ask whether the money is protected if the firm stops trading. Some traders charge to prepare a quote, so ask before they visit. A bay is a made-to-measure frame. Ask who owns it if you pay before it arrives.
Will the quote include VAT?
Only a VAT-registered business has to add VAT. GOV.UK says you must register when taxable turnover for the last 12 months goes over £90,000. Citizens Advice says the written quote should state whether VAT is included. Ask for one total that a second fitter can be compared with. A supply-only frame and a supply-and-fit frame are different jobs.
Does QuoteZila check the businesses?
No. We don't check insurance, qualifications or registrations, so please check these yourself before you hire. You can report a quote or a business from your job page.
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Related pages
- Velux Window Work in Cheshire: What to Ask. A standard roof window is around £980 to £1,200 in the Federation of Master Builders loft guide of 3 September 2025. QuoteZila does not set prices.
- Window Glass Replacement: What Affects Cost. Replacing a sealed unit or a single sheet of glass in Cheshire: what changes a glazier's quote, where safety glass is needed and what paperwork to ask about.
Sources
- QZ1: QuoteZila product fact. QuoteZila public pricing line.
- QZ2: QuoteZila product fact. QuoteZila terms, customers.
- QZ5: QuoteZila product fact. QuoteZila coverage wording.
- S1: Planning permission: doors and windows, Planning Portal. Accessed 2026-10-25. https://www.planningportal.co.uk/permission/common-projects/doors-and-windows/planning-permission
- S2: Building Control Guidance Note 05, Lancaster City Council. Accessed 2026-10-25. https://www.lancaster.gov.uk/assets/attach/1344/Leaflet-5-Replacement-Windows-to-Dwellings.pdf
- S3: Building work, replacements and repairs to your home, GOV.UK. Accessed 2026-10-25. https://www.gov.uk/government/publications/building-work-replacements-and-repairs-to-your-home/building-work-replacements-and-repairs-to-your-home
- S4: Building regulations: doors and windows, Planning Portal. Accessed 2026-10-25. https://www.planningportal.co.uk/permission/common-projects/doors-and-windows/building-regulations
- S5: Before you get work done on your home, Citizens Advice. Accessed 2026-10-25. https://www.citizensadvice.org.uk/consumer/getting-home-improvements-done/before-you-get-building-work-done/
- S6: Register for VAT, GOV.UK. Accessed 2026-10-25. https://www.gov.uk/register-for-vat