Question 1

How much does it cost to replace windows in the UK?

Accepted Answer

Checkatrade puts the average cost of new double glazing for a typical 3-bed house at £8,000–£15,000, usually for 8–12 windows — roughly £1,000–£1,250 per window installed for standard uPVC casements. Those consumer figures are VAT-inclusive; our calculator works from ex-VAT trade costs and then adds the standard 20% VAT on top, so the headline total is the real bill you pay. Larger bay or bow windows, premium frames, and full-frame replacement push the total higher.

Question 2

What's the difference between insert and full-frame replacement?

Accepted Answer

An insert (retrofit) window fits inside the existing frame and is faster and cheaper. Full-frame replacement strips the old frame back to the opening, adding removal and trim labour, and is the right choice when the existing frame is rotten or you're changing the window size. Toggle 'Full-frame replacement' to include that extra labour.

Question 3

Do I need FENSA or building-control sign-off for new windows?

Accepted Answer

In England and Wales replacement windows must meet Building Regulations (energy efficiency and, on certain windows, fire escape and ventilation). Most installers self-certify through a competent-person scheme such as FENSA or CERTASS, which avoids a separate building-control application. Scotland operates a separate building-standards regime where like-for-like replacement is often exempt — check with your local council.

Item	Estimate
Old window removal	£1,050
Window unit	£4,700
Installation labor	£2,650
Trim, flashing & finish	£880
Disposal	£300
Subtotal	£9,580
VAT (20%)	£1,916
Total inc. VAT	£11,496

Window Replacement Cost Calculator

Window Replacement Cost by region