Sash window replacement quotes from local installers
Get free sash window replacement quotes: a full new window, new sashes in the old box, or restoration. Local installers who cover your postcode survey every opening and quote in writing.
- Say "sash" on the call. Pick timber or uPVC in the form, then say the windows are sashes on the confirmation call when they ring to confirm
- Replace, new sashes or restore: a 9-point checklist for every quote
- Free and no obligation. Say no to every quote if none suit you
We are a free quote-matching service, not an installer.
Four ways to quote
Replace the window, fit new sashes or restore: what to ask for
Ask for a full new window, new sashes in your existing box frame, or restoration of the windows you have, and add secondary glazing where consent rules out replacement. Each installer prices them differently, so ask every installer to quote the same option.
Full replacement
A full replacement removes the old box frame and sashes and fits a complete new window, in timber or uPVC. Ask the installer to quote this when the box frame is rotten or you want a different material.
New sashes in the old box
New sashes fit into a sound existing box frame, often with double glazed units, while the box stays in the wall. Many sash specialists offer this, so ask the installer to quote it as its own line.
Restoration
Restoration repairs the existing timber, replaces cords and adds draught proofing, keeping the original windows. Ask the installer to quote each repair separately.
Secondary glazing
Secondary glazing adds a separate inner pane behind the original sash, for homes where consent rules out replacement. Approved Document L accepts single glazing with low-emissivity secondary glazing where a window has to keep its character.
Is it worth repairing sash windows?
Repairing sash windows is worth it when the box frame and sill are sound, and replacement is the better call when the box frame itself has failed. Check five parts before you ask for quotes, and ask for the matching quote:
| Part | What you see | Quote to ask for |
|---|---|---|
| Box frame | Sound timber, or soft and rotten through | Sound: new sashes or restoration. Rotten: full replacement |
| Sill | Firm, or split and soft | Ask whether a sill repair or a new sill is priced as its own line |
| Sashes | Tight joints, or loose joints and rot in the rails | Loose or rotten: new sashes in the old box |
| Cords and pulleys | Smooth running, or broken cords and sashes that drop | Restoration, with new cords and draught proofing |
| Glass | Single glazing, or misted double glazing | New double glazed sashes, or secondary glazing where consent is tight |
The installers we pass enquiries to quote for replacement windows. For repair-only work on original timber, a sash restoration joiner is the better fit. Our window replacement London page covers when to refurbish, secondary glaze or replace a sash in the 29.2% of London homes built before 1919.
Step by step
How to replace sash windows: step by step
Replace sash windows in eight steps, from the consent check to the certificate.
- Check consent first. Ask your council whether the house is listed, in a conservation area or under an Article 4 direction.
- Choose the route. Full replacement, new sashes in the old box, restoration or secondary glazing, using the condition check above.
- Book surveys. Each installer measures every opening and checks the box, sill and lintel before pricing.
- Compare written quotes. Each quote prices the same route, material, mechanism and glass per window.
- Agree the deposit and read the contract. If you sign at home, you usually have at least 14 days to cancel, but made-to-measure windows can be an exception, so check the contract before you sign.
- Ask the lead time. Sash windows are made to measure, so get the manufacture and fitting dates in writing.
- Fit and make good. The quote states who removes the old windows and who repairs plaster, paint and sills inside and out.
- Get the sign-off. A FENSA or CERTASS installer registers the job and you receive a certificate. Otherwise building control signs it off.
Timber or uPVC
uPVC or timber sash windows: which your home allows
Your home's listing and planning status decide whether uPVC or timber sash windows are allowed. A listed building needs listed building consent for any significant works, and an Article 4 direction brings replacement windows under planning control. Basingstoke has Article 4 directions on windows in four conservation areas, as our page on double glazing in Basingstoke explains.
Are uPVC sash windows any good?
uPVC sash windows are a sound choice where your council allows them and the quote names the profile system, the mechanism, and horns and glazing bars that match the originals. Ask to see a fitted example before you sign.
Which type of sash windows are better, uPVC or wood?
Neither uPVC nor wood is better for every house: the better choice is the material your council allows that meets the specification you want. Check listed status and any Article 4 direction with the council before you pick uPVC.
What changes on the quote
| Material | Quote should name | Ask |
|---|---|---|
| Timber sash | Timber type, finish, mechanism | What maintenance keeps the guarantee valid? |
| uPVC sash | Profile system, mechanism | Do the proportions and horns match the originals? |
| Either | Glass unit and its rating | Is it slimline or standard double glazing? |
The spec
What a sash window replacement quote should include
A sash window replacement quote names the sash mechanism, the frame material, the glass rating and the detailing for every window, after a survey of each opening. Check for these nine items:
- Each window measured and drawn, with its size and pane layout
- Box sash with weights and pulleys, or spring balances
- Timber type, or the uPVC profile system by name
- Glass spec with a U-value or Window Energy Rating per window
- Glazing bar style: through bars or bars fixed to the glass
- Horns, sills and other detailing matched to the house
- Removal of the old windows and making good inside and out
- Who applies for any planning or listed building consent
- The guarantee length for each part: joinery or frame, glass unit, paint finish, draught strips and mechanism
In England, replacement windows must reach a U-value of 1.4 W/m²K or a Window Energy Rating of band B. To line the quotes up, use our guide on how to compare double glazing quotes.
Box sash or spring balance: name it on the quote
A box sash slides on cords running over pulleys to hidden weights inside a timber box frame. This is the traditional mechanism in Georgian, Victorian and Edwardian houses.
A spring balance sash slides on tracks held by springs in the frame, with no weights or box. Spring balances are usual on uPVC sash windows, so ask which mechanism each quote prices.
Glazing bar patterns differ by period too, so ask for the bar layout to match the originals.
Permission first
Sash windows in listed buildings and conservation areas
Listed buildings need listed building consent for any significant works, inside or out, so check with your council before you sign a sash window quote. In England, new windows of similar appearance usually need no planning permission. Three things change that:
- Listed building: listed building consent from the council
- Article 4 direction: removes permitted development, so planning permission applies
- Conservation area: extra local restrictions may apply
FENSA cannot register work on Grade I listed properties, so ask the installer how building control signs off the job there. These are the rules for England. Scotland and Wales run their own systems, so ask your council there. Our pages on Edinburgh double glazing quotes and double glazing in Cardiff cover sash windows under the Scottish and Welsh rules.
When a sash cannot reach 1.4
Approved Document L allows two alternatives where keeping the building's character stops a window meeting 1.4 W/m²K: a centre pane U-value of 1.2 W/m²K or better, or single glazing with low-emissivity secondary glazing.
Ask each installer which route the quote follows, and who agrees it with building control. The replacement opening must also give at least the same means of escape as the old one. Oxford has 195 grade I listed entries, and our page on double glazing quotes in Oxford covers secondary glazing for listed homes.
Who to hire
Choosing a sash window installer
Choose an installer who makes or fits sash windows regularly and can show period work, then run five checks before you sign.
Five checks
- Sash or joinery experience, not only casements
- Photos or addresses of period jobs you can see
- FENSA or CERTASS registration in England and Wales
- An insurance-backed guarantee, named in writing
- A written quote that itemises every window
More on installers
The same scheme checks apply to every window job. Our page on double glazing installers covers the survey and the sales tactics to avoid. The questions to ask a double glazing salesman work for sash specialists too.
Before you sign, read about the double glazing cooling off period.
Period housing
Sash window replacement by city
Older housing means more sash windows to replace or repair. These local pages cover the planning controls and housing in each area.
- Double glazing quotes in London: pre-1919 terraces and borough Article 4 directions.
- Double glazing quotes in Bristol: older homes and the council's traditional windows guidance.
- Double glazing quotes in York: listed buildings and conservation areas.
- Double glazing quotes in Liverpool: Article 4 directions on windows in conservation areas.
- Double glazing quotes in Glasgow: sash and case windows in tenements, under Scottish rules.
Related pages
FAQ
Sash window replacement: common questions
More buying advice, from timing to contracts, is in our double glazing buying advice.
Can you replace window sash only?
Yes, many sash specialists fit new sashes into a sound existing box frame, often with double glazed units, while the box stays in the wall. Ask for it as its own quote, alongside a full replacement quote, and ask whether the job gets a FENSA or CERTASS certificate or needs building control sign-off.
How can I replace my sash windows?
Replace sash windows by checking consent with your council, choosing the route, getting surveys and itemised written quotes, then having a registered installer fit and certify the windows, as in the eight steps above.
How much does it cost to replace old sash windows?
Each installer prices your sash windows after a survey, so compare written quotes; for typical figures, see what sash windows cost on our sister site.
Can I get a sash window quote online?
You start online, but the written quote follows a survey. Each installer measures every opening, checks the box and sill, and then prices the windows in writing.
Do I need permission to replace sash windows?
Listed buildings need listed building consent. Homes under an Article 4 direction need planning permission. Elsewhere in England, new windows of similar appearance usually need no planning permission. Check with your council before you sign.
Can replacement sash windows meet Building Regulations?
Yes. Replacement windows in England must reach a U-value of 1.4 W/m²K or Window Energy Rating band B. Where a building's character has to be kept, Approved Document L accepts a centre pane U-value of 1.2 W/m²K or secondary glazing instead.
Get your sash window replacement quotes
Answer a few questions, say the windows are sashes on the confirmation call, then compare written quotes from local installers.
Get free quotes
Sources
- Approved Document L, Volume 1 (2021 edition incorporating 2023 amendments), Table 4.2 and paragraph 4.10; the 2026 edition (in force 24 March 2027) keeps both values
- Planning Portal, doors and windows: planning permission and Building Regulations
- GOV.UK, competent person schemes
- FENSA Help Centre, An Overview (Grade I listed properties are out of scope), checked 1 October 2026
- Consumer Contracts Regulations 2013, regulation 28