The 1930s bay window replacement cost is £1,500 to £3,500 in 2026 on MyJobQuote's quote data, a little above a standard uPVC bay. The extra comes from larger, non-standard openings and original timber frames, and from what the old bay may be holding up. Price your bay, then get free quotes from local installers who check the structure first.
Why a 1930s bay costs more
| Bay | Fitted price | Source |
|---|---|---|
| 1930s bay replacement | £1,500 to £3,500 | MyJobQuote, September 2026 |
| Standard uPVC bay | £1,250 to £3,000 | Site benchmark, 2026 |
MyJobQuote says its figures come from quotes homeowners submit to it. The standard bay range is the one our calculator uses.
MyJobQuote gives two reasons. Many 1930s bays have larger, non-standard openings, and many still have their original timber frames. If a frame has rotted or the brickwork around it is damaged, repairs may be needed before the new bay goes in.
Is the old bay holding the house up?
This is the question that decides the price. A good surveyor measures the opening and then checks how the bay is supported.
- The GGF tells installers to work out the loads in the existing bay and specify bay poles to suit them.
- FENSA says most replacement frames cannot carry load without extra support, and that bays need temporary props while the work is done.
Ask for the support as its own line. The steps on the day are set out in our Bay Window Replacement guide.
The bay roof
The small roof over the bay does not always have to go. MyJobQuote says an installer may keep one that is solid, watertight and properly supported, and will likely advise replacing it if there is rot, sagging or a leak. Ask whether your quote includes it.
Keeping the 1930s look
Crittall, which makes steel windows, says steel was becoming the material of choice in the 1930s and that bays often had grids of small panes divided by glazing bars. Its advice for a replacement bay is to match the original proportions of frame to glass. As a steel maker, it also says uPVC and aluminium frames come out thicker.
The Planning Portal says new windows of a similar appearance to the house's do not usually need planning permission. In a conservation area or under an Article 4 direction, check with your council first.
Get free quotes for your 1930s bay
Tell us about the bay and we pass your details to local installers covering your area, who will contact you to arrange a survey.
Questions before you book
How much does it cost to replace a 1930s bay window?
MyJobQuote puts it at £1,500 to £3,500 in 2026, based on quotes homeowners submit to it. That sits a little above the £1,250 to £3,000 we use for a standard uPVC bay, because many 1930s bays have larger, non-standard openings and original timber frames.
Are 1930s bay windows load-bearing?
Some are, and nobody can tell you which without looking. The GGF tells installers to work out the loads in the existing bay before removing it and to specify bay poles to suit them, and FENSA says most replacement frames cannot carry load without extra support.
Should I replace the bay roof at the same time?
Only if it needs it. MyJobQuote says an installer may keep a bay roof that is solid, watertight and properly supported, and will likely advise replacing it if there are signs of rot, sagging or leaks.