Sash Window Repair Cost in London: 2026 Price Guide
Updated 12 June 2026|8 min read
Repairing a sash window in London costs from £150 for a simple fix to £900 or more for a full overhaul per window. Replacing a broken sash cord or balance runs about £100–£150, draught-proofing a window is a few hundred pounds, and a complete refurbishment is typically £620–£920. Retrofitting slim double-glazing into period sashes can reach £1,500 each. This guide breaks down the costs job by job, with the conservation-area points London owners need to know, so you can budget before booking a free survey.
How much does sash window repair cost in London?
Sash window repair costs span a wide range because the jobs vary enormously, from a fifteen-minute cord swap to a full strip, repair and overhaul. A simple repair, easing a stuck sash, replacing beading or a small section of timber, starts around £150. A full overhaul of a tired window, with new cords, repairs to the timber, draught-proofing and re-balancing, lands at £620–£920.
Replacing a broken sash cord or spiral balance is one of the most common jobs at £100–£150 per window. Draught-proofing a single window with brush seals typically costs £150–£300. Retrofitting slim double-glazing into existing or new sashes can reach up to £1,500 per window.
London adds 25–40% over national rates, reflecting higher joiner day rates, access, scaffolding for upper floors and parking. The table below shows typical costs by job, excluding VAT which we itemise separately.
Sash window job
Typical London cost (2026)
Simple repair (easing, beading, minor timber)
£150 – £300
Sash cord / spiral balance replacement
£100 – £150
Draught-proofing (per window)
£150 – £300
Full window overhaul / refurbishment
£620 – £920
Slim double-glazing retrofit
up to £1,500
Sash cord and balance replacement
A snapped sash cord is the classic sash window failure, the window suddenly will not stay up, or one side drops. Replacing a cord costs £100–£150 per window because, although the part is cheap, the job involves carefully removing the staff bead and parting bead, dropping out the sashes, and re-threading new cord over the pulleys onto the weights inside the box frame.
Newer or converted windows may use spiral balances rather than cords and weights. These wear out too and are replaced as a pair, at a similar cost.
When we replace a cord we usually recommend doing both sides at once, even if only one has snapped, because the second is likely the same age and will go soon, and the labour of opening the window is already done. It is the more economical approach over the life of the window.
Draught-proofing your sash windows
Original sash windows are draughty by nature, and draught-proofing is one of the best-value improvements you can make at £150–£300 per window. It involves routing discreet brush or wiper seals into the meeting rails and the channels the sashes slide in, sealing the gaps without changing the window's appearance.
The benefits are immediate: less heat loss, lower bills, fewer draughts and a noticeable cut in noise and dust, which matters on busy London streets. Done well, draught-proofing also makes the sashes run more smoothly than before, because the channels are cleaned and refurbished as part of the work.
Draught-proofing is often combined with a cord replacement or overhaul, since the window is already being taken apart. Bundling these jobs together is more cost-effective than calling a joiner out separately for each.
Full sash window refurbishment
A full refurbishment, typically £620–£920 per window, is the answer when a sash window is tired but the timber is fundamentally sound, which is true of most original London sashes. Old softwood and hardwood were far more durable than modern timber, which is exactly why repairing a period window usually beats replacing it.
A refurbishment involves removing both sashes, stripping back old paint, splicing in new timber where there is decay, repairing or renewing the cords and pulleys, draught-proofing, re-puttying or re-beading the glass, easing and adjusting the runs, and repainting. The result is a window that opens smoothly, seals well and lasts another few decades.
It is more cost-effective than full replacement, preserves the character and value of a period property, and avoids the planning headaches replacement can trigger in conservation areas. We assess each window honestly and refurbish where the timber allows.
Conservation areas and listed buildings
If your home is in a conservation area or is listed, and a great many London period properties are, this directly affects what you can do to your sash windows. Repair and like-for-like refurbishment are almost always fine and usually the preferred option, because they retain the original windows.
Replacement is where you must be careful. In a conservation area, replacing timber sashes with uPVC, or altering the glazing bars and proportions, can require planning permission and may be refused. Listed buildings need listed building consent for almost any change to the windows. Getting this wrong can mean enforcement action and being made to reinstate at your own cost.
This is a strong practical reason to repair rather than replace. We work to retain and refurbish original sashes, which keeps you on the right side of conservation rules while preserving the look that makes period London homes desirable.
Repair or replace: which makes sense?
The instinct to rip out old windows for shiny new ones is usually the wrong call for a London sash window. Original sashes were made from slow-grown, dense timber that, once repaired and maintained, outlasts modern replacements. Repair and refurbishment typically cost a fraction of replacement and keep the character that adds value to period homes.
Replacement makes sense only when the timber is extensively rotten beyond economic repair, or when you want the thermal performance of full double-glazing and the property's conservation status allows it. Even then, a new timber box sash is preferable to uPVC in most London streets, both for appearance and for resale.
For owners wanting better thermal comfort without replacement, slim double-glazing retrofitted into existing sashes, plus draught-proofing, gets most of the way there while keeping the original windows. We will give you a straight assessment of whether your windows are worth repairing, and they very often are.
Get a fixed quote for your sash windows
Sash window pricing depends on the condition of the timber, the cords and pulleys, the glazing and the access, none of which can be judged from the street, so an accurate quote needs a survey. We inspect each window, test the runs and probe the timber for decay, then price the right level of work.
Your written quote will set out exactly what each window needs, whether a simple repair, a cord replacement, draught-proofing or a full overhaul, with the finish and VAT shown separately. Where you have several windows, we price them together, which is more economical than one visit per window.
Book a free survey with London Refurbishments & Leak Repairs and we will assess your sash windows, advise on repair versus refurbishment, flag any conservation considerations, and give you a clear fixed written quote.
Frequently Asked Questions
How much does it cost to repair a sash window in London?
Repairing a sash window in London costs from £150 for a simple fix to £900 or more for a full overhaul per window in 2026. A cord or balance replacement is £100–£150, draught-proofing £150–£300, and a complete refurbishment £620–£920. Slim double-glazing retrofit can reach £1,500 per window. Figures exclude VAT.
How much does it cost to replace a sash cord?
Replacing a broken sash cord costs £100–£150 per window in London. Although the cord itself is inexpensive, the job involves removing the beads, dropping out the sashes and re-threading the cord over the pulleys onto the internal weights. We usually recommend replacing both cords at once, as the second is likely to fail soon.
Is it cheaper to repair or replace sash windows?
Repairing is almost always cheaper and usually better. A full refurbishment at £620–£920 per window costs a fraction of replacement and keeps the original timber, which on a period London home is denser and more durable than modern alternatives. Replacement only makes sense where the timber is rotten beyond economic repair.
Do I need permission to repair sash windows in a conservation area?
Like-for-like repair and refurbishment of sash windows generally do not need permission, even in a conservation area, which is one reason repair is preferred. Replacing timber sashes with uPVC or altering the glazing bars can require planning permission and may be refused, and listed buildings need listed building consent for changes.
Can you draught-proof old sash windows?
Yes. Draught-proofing routes discreet brush seals into the meeting rails and sliding channels, sealing gaps without changing the window's appearance, at £150–£300 per window. It cuts heat loss, noise and dust and makes the sashes run more smoothly. It is often combined with a cord replacement or overhaul to save on labour.
