What It Costs
Sash window prices are confusing because two firms can quote wildly different figures for something they both call “draught proofing”, and both be quoting honestly. The difference is almost always scope. This page sets out the published market ranges, explains what moves a quote up and down, and gives you a short list of questions that will make two quotes actually comparable.
We do not publish a fixed price list, because the honest answer depends on the window. What we do instead is look at the windows and give you a firm written price before any work starts, free and with no obligation. The figures below are the wider London market, gathered from firms' own published price lists, so you can sanity-check whatever you are quoted — by us or by anyone else.
First: the two very different jobs called “draught proofing”
This single distinction explains most of the price spread you will see.
Draught stripping only
Seals are added to a window that is already in reasonable working order. No overhaul, no new cords, no re-balancing. Published London rates for this start from around £80 per box frame. It is cheap because it is a fraction of the work — and it is only suitable if the window is already sound. If your cords have gone or the sashes are stiff, this is not the job you need, and a firm quoting it will usually say so in the small print.
Full draught proofing with an overhaul
The sashes come out, the window is serviced, cords are renewed, the sashes are re-balanced, and new parting and staff beads with pre-installed brush pile go back in. This is the job described on our draught proofing page, and it is what most people actually want. Published London ranges are roughly £328–£588 per window for a standard sash and £488–£888 for a large one.
A cheap quote is not automatically a bad one — but if one quote is a quarter of another, check whether it includes taking the sashes out and renewing the cords. Usually it does not.
Published London price ranges
Gathered from London sash specialists' own published price lists, most recently dated March 2025. Treat them as a market sanity-check rather than a quote.
| Job | Published London range | Notes |
|---|---|---|
| Draught stripping only, per box frame | from ~£80 | No overhaul, no cords, no balancing. Sound windows only. |
| Draught proofing, standard sash (under ~1.8m × 0.9m) | £328 – £588 | Typically includes service, new cords, furniture and sealed beads |
| Draught proofing, large sash | £488 – £888 | |
| Draught proofing, Venetian sash | £888 – £1,388 | Three-part window, much more work |
| Draught proofing a whole bay | £900 – £1,500 | Depends on size and access |
| Overhaul (cords, counterbalancing, pulleys, putty) | £280 – £480 | Without draught proofing |
| Overhaul + draught proofing + decoration | £820 – £1,020 | The common “do it once, properly” package |
| Sash cords, lower sash, standard size | £280 – £480 | Per sash (two cords), with convenient access |
| Sash cords, upper sash, large | £420 – £620 | Per sash |
| Sill splice | £180 – £300 | Rot repair, per section |
| Sill replacement | £250 – £450 | |
| Full window replacement | £2,080 – £3,380 | For comparison — usually the last resort |
Two things to note about those figures. Some London firms operate a minimum call-out charge — one publishes £500 + VAT — which is why a single window is poor value and several windows together are much better. And published lists vary in whether they include VAT, so always confirm.
As a third-party cross-check, Checkatrade's 2026 cost guide puts professional sash draught proofing at £248–£388 per window, averaging around £318 — which sits at the lower end of the specialist lists above and is a fair reflection of the middle of the market.
Sash cords: two different markets, two different prices
This trips people up more than anything else on this page. There are two genuinely different ways to buy sash cord work in London, and the prices are not comparable.
The fixed-price repair tier
Firms that do cords as a standalone call-out, often same-day, at a published fixed price and usually with no call-out fee. Published London rates run roughly:
| Scope | Published fixed price |
|---|---|
| One cord | £70 – £130 |
| Both cords, one sash | £95 – £180 |
| All four cords in a window | £150 – £230 |
Note how the per-cord rate falls sharply as you do more — one firm's list works out at £100 for one cord but £50 a cord if you do all four, because the access is the same either way. Watch for VAT: some of these lists are quoted ex VAT and some do not say.
The specialist joinery tier
Firms that only touch cords inside a full sash-out overhaul, often under a substantial minimum call-out. Published London rates are £280–£480 per sash for a standard lower sash with good access, rising to £440–£780 for a large upper sash or where there is nowhere to park.
Neither is a rip-off. They are different services. If a cord has snapped on an otherwise sound window and you just want it working again, the fixed-price tier is the sensible buy. If the window is tired all over — stiff, rattling, draughty, beads past it — paying the fixed-price tier four times over the next few years costs more than having it overhauled once. What you should not do is take a £95 quote as evidence that a £400 quote is dishonest without asking what each includes.
A VAT point almost nobody mentions
Draught stripping is on HMRC's list of energy-saving materials, which means the draught-proofing element of the work is currently zero-rated for VAT under VAT Notice 708/6 — the relief runs to 31 March 2027, after which it reverts to the reduced rate of 5%.
That does not mean the whole invoice is VAT-free. The other parts of a sash overhaul — cord replacement, pulley work, rot repair, decoration — are standard rated at 20%. So a properly drawn invoice for a combined job should show a split. Be wary of anyone quoting a single flat VAT rate across the lot, in either direction: we have seen firms advertise 5% on the whole job and others charge 20% on all of it, and neither matches the guidance. See HMRC VAT Notice 708/6.
Why you should ignore the £250 figure you may have read
The Energy Saving Trust puts professional draught proofing of a whole house's windows and doors at around £250. That figure is real, but it is for ordinary strip and brush draught proofing across a normal house — it is not a price for specialist sash window work, where the sashes come out and the beads and cords are renewed. If you arrive at a sash specialist expecting £250 for a Victorian terrace, the quote will be a shock. The £80-per-frame strip-only service is the nearest equivalent.
What moves the price
- How many windows. Much the biggest factor. Setting up, protecting the room and getting tools in is a fixed cost that gets shared. Six windows in one visit cost far less per window than one window on its own.
- Size and type. A large sash, a bay, a Venetian or a curved head is more work than a standard two-over-two.
- Access. Upper floors, no parking, scaffolding or a tower. One London price list charges noticeably more for the same sash where there is no parking — that is not a surcharge for its own sake, it is real lost time.
- Condition. Rot, splitting, previous bad repairs and missing weights all add. Windows that have been painted shut for decades take longer to free.
- Scope. Whether decoration is included. Repainting is a significant part of a full package and is often quoted separately.
- Combining jobs. This one works in your favour — see below.
Where you genuinely save money
- Have the cords and the draught proofing done together. Both jobs need the paint seal cut, the beads off and both sashes out. That access is most of the labour. Done together it is one operation; done a year apart you pay for it twice. Published packages reflect this: an overhaul is £280–£480 and draught proofing is £328–£588, but the combined package with decoration is quoted at £820–£1,020 — less than buying the parts separately and getting the painting free.
- Do several windows in one visit. The single most effective lever, and it also gets you past any minimum call-out charge.
- Do the cheap DIY jobs yourself first. Sealing the frame to the wall and sorting the meeting rail fastener cost a few pounds and sometimes solve the problem entirely. Our DIY page is honest about which jobs are worth doing yourself.
- Do not pay to strip a window that needs overhauling. Cheap seals on a worn window fail, and then you pay again.
Repair versus replacement
Full replacement of a sash window runs to roughly £2,080–£3,380 on published London lists, against £328–£888 to draught proof and overhaul the one you have. On the energy side the case for replacement is weaker than people assume: the Energy Saving Trust puts A-rated double glazing throughout an entirely single-glazed semi at around £4,800, saving about £85 a year.
Historic England's position is that draught proofing gives the biggest energy and conservation benefit for the lowest financial and environmental cost, and that improvements beyond repair and draught sealing may not be cost effective in either financial or carbon terms. On a listed building or in a conservation area, replacement may not be permitted at all.
How to compare two quotes properly
Ask both firms the same six questions and the cheaper quote will often turn out to be the dearer one:
- Do the sashes come out of the frame, or is this seals fitted in situ?
- Are new sash cords included, and on how many sashes — two or all four?
- Are new parting beads and staff beads included, with the pile built in, or are you getting seals fitted into the existing beads?
- Are the sashes re-balanced against the weights afterwards?
- Is making good and decoration included, or extra?
- Is that price including VAT, is the draught-stripping element zero-rated, and is there a minimum call-out charge?
Frequently asked questions
How much does it cost to draught proof a sash window in London?
Published London ranges are about £328–£588 for a standard sash and £488–£888 for a large one, where the job includes taking the sashes out, renewing the cords and fitting sealed beads. A strip-only service on a window already in good order starts from around £80 per box frame.
How much is it to replace a sash cord?
It depends which of the two markets you buy in. Fixed-price repair firms publish roughly £70–£130 for a single cord and £150–£230 for all four in a window. Specialist joiners who only do cords as part of a sash-out overhaul publish £280–£480 per sash. Both are real prices for different scopes — see the section above. In either case, doing all four cords costs far less than twice doing two, because the access is the same.
Why is one quote £80 and another £500 for the same window?
Because they are not the same job. The £80 figure is seals only, on a window that is already working properly. The £500 figure takes the sashes out, overhauls them, renews the cords and fits new sealed beads. Ask the six questions above.
Is it cheaper to do the whole house at once?
Considerably, per window. The access and setting up is shared, and it gets you past any minimum call-out charge. If the budget will not stretch to all of them, do a whole floor or the rooms you actually sit in rather than one window here and there.
Will draught proofing pay for itself?
Not quickly, on fuel savings alone — and anyone promising otherwise is selling. The Energy Saving Trust's figure for draught proofing a whole home's windows, floors and doors is around £55 a year. People have this work done because the room stops being cold and draughty to sit in, the rattling stops, and the window works again. Those are the real returns.
Do you charge for a quote?
No. Estimates are free and carry no obligation.
Price ranges above are other firms' published London rates, most recently dated March 2025, collected as a market comparison. They are not our quotes and they will have moved since. Energy figures: Energy Saving Trust (draught proofing, windows and doors); conservation position: Historic England.
Want a real number for your windows? Send the postcode, how many windows and what they are doing through the contact form. A photo or two helps. The estimate is free.