Windows
Sash windows
Sliding sash windows cost roughly £800 to £1,800 each fitted, more than a casement because the mechanism is more complex. They slide vertically rather than swinging open and are the correct style for Georgian, Victorian and Edwardian houses, where a casement replacement looks obviously wrong.
Sash windows are where the repair-versus-replace question is most worth asking. A sound original box sash can often be refurbished for less than replacement, and in a listed building that may be the only option available to you.
Indicative guide, not a quote
per window, supplied and fitted
£800 – £1,800
These figures come from published industry price guides, not official statistics, and several of those sources are installers or comparison sites with a commercial interest. They are a starting point for a conversation, not a quote. Your installer sets the actual price after measuring.
Checkatrade double glazing cost guide · checked 2026-10-09
Cords and weights, or spiral balances
A traditional box sash runs on cords over pulleys with cast iron weights hidden in the frame. It is repairable almost indefinitely and is what a conservation officer will expect in a listed building.
Modern replacements usually use spiral balances instead: a spring mechanism in the frame that does the same job in a much slimmer box. It is cheaper and works well, but it is visibly not a traditional sash up close.
Repair before you replace
Sash windows were built to be taken apart. Rotten sections of sill or sash can be cut out and spliced, cords replaced, and the whole thing draught-proofed with brush seals that make a substantial difference to comfort without changing the appearance.
Refurbishment with draught-proofing is often materially cheaper than replacement and keeps the original glass, which in an older house is part of the character.
Getting double glazing into a sash
Standard sealed units are too thick for most original sash rebates. Slim-profile units, typically around 11 to 14mm overall, are made for exactly this and fit where a standard unit will not.
They perform less well than a full-thickness unit, so the honest comparison is against the single glazing you have now, not against a new casement.
Sash windows: common questions
- Can I put uPVC sash windows in a conservation area?
- Sometimes, but do not assume it. Many authorities refuse uPVC in conservation areas, and an Article 4 direction can remove the permitted development rights you would otherwise rely on. Ask the conservation officer first.
- Is it cheaper to repair sash windows than replace them?
- Frequently, yes, where the boxes and sills are sound. Repair plus draught-proofing addresses most of the comfort complaints without the cost or the consent problems of replacement.
- Do sash windows rattle?
- Old ones do, because the sashes have shrunk away from the staff beads. Brush-pile draught-proofing closes that gap and removes both the rattle and most of the draught.
Other windows
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uPVC windows
£400 – £850 fitted
uPVC windows cost £400 to £850 fitted. What separates a good one from a cheap one, what the regulations require, and when uPVC is the wrong choice.
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Aluminium windows
£600 – £1,250 fitted
Aluminium windows cost £600 to £1,250 fitted. Why the slim sightlines matter, what a thermal break does, and whether the extra over uPVC is worth it.
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Timber windows
£800 – £1,600 fitted
Timber windows cost £800 to £1,600 fitted. Why modern engineered timber is not the wood you remember, the real maintenance, and when it is compulsory.
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Casement windows
£400 – £850 fitted
Casement windows are the most common UK style and the cheapest to replace. Side-hung or top-hung, fire escape rules, and flush versus stormproof.
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Tilt and turn windows
£400 – £850 fitted
Tilt and turn windows open two ways: a secure vent, or fully inwards for cleaning and escape. Why flats and upper floors usually choose them.
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Bay and bow windows
£1,500 – £3,000 fitted
Bay and bow windows cost £1,500 to £3,000 fitted because many carry structural load. The difference between them and what a survey must check.
TrustedGlazing does not make, supply or fit windows and doors, and the prices above are published industry guides rather than our own. We match your enquiry to one vetted local installer, who quotes and contracts with you directly.