What This Covers, and What It Doesn't
This service covers repair, restoration, draught-proofing and, where genuinely necessary, like-for-like replacement of timber box sash windows, plus internal joinery: doors, linings, architrave, staircases, skirting and picture rail. On the sash window side that means easing and re-hanging sashes that have been painted shut, replacing snapped or perished sash cords, splicing out rotten sections of sill, bottom rail or pulley stile rather than replacing the whole frame where the rest of the timber is sound, re-puttying and re-glazing single-glazed sashes, and fitting brush-pile draught-proofing into the running channels. On the joinery side it covers supplying and fitting standard internal doors, whether that's a flush door for a modern flat or a period-matched four-panel door for a Victorian house, along with door linings, architrave, and staircase repair or replacement where treads, spindles, handrails or the stringer itself have worked loose or rotted. What this page does not cover is double glazing manufactured into a new uPVC or aluminium frame, which is a different product with a different planning and thermal-performance profile, and it does not cover fire-rated doorsets: FD30 and FD60 certificated door sets for HMOs, converted blocks and fire risk assessment action plans are priced and fitted to a completely different specification, covered on our <a href='/fire-doors-london'>fire door installation page</a>, and shouldn't be confused with a standard internal door even though both look similar from the front.
Why London's Housing Stock Fails This Way
Box sash windows were the standard window for London houses from the Georgian period right through to around 1910, and a huge proportion of Victorian and Edwardian terraces still have their original sashes, or at least sashes built to the original pattern during a later repair. The construction itself, a pair of sashes running in timber boxes on a system of cords, pulleys and cast-iron weights, is mechanically simple and genuinely repairable almost indefinitely provided water hasn't got into the timber for years at a time. The recurring failure is water ingress at the sill and bottom rail, where the horizontal end grain sits exposed to weather at the lowest point of the frame, plus perished putty around the glass letting water track down inside the sash before it ever reaches the sill. Decades of gloss paint applied without stripping the old coats back first also builds up in the running channels between sash and box, which is why so many original sashes in London houses have been painted shut for years and get mistaken for windows that don't open at all, when in fact the sash and cords underneath are usually still sound. Ex-council flats and 1930s semis further out from central London are more likely to have had their original sashes already replaced with casement or uPVC windows at some point in the building's history, so joinery work on those properties is more often about internal doors and staircases than sash restoration.
What Drives the Cost, Line by Line
Brush-pile draught-proofing to an existing sash in reasonable condition, no cord or timber repair needed, runs £250–£450 per window in London, reflecting higher labour and scaffold or access costs than the £150–£350 typical of the rest of the country. A fuller restoration, new sash cords, easing and re-hanging, re-puttying, draught-proofing and repainting where the timber itself doesn't need splicing, is typically £400–£900 per window. Where rot has got into the sill or bottom rail and needs cutting out and splicing in new timber, add roughly £150–£250 per repair on top of the restoration cost, since splicing is a skilled joinery repair in itself, not a quick patch. Sash cord replacement on its own is priced by how many cords need doing: roughly £70 for a single cord, £95–£115 for a pair, up to about £150 to replace all four cords in one window. A bespoke like-for-like replacement sash, built and glazed to match the original horns, glazing bars and putty line where the existing frame is too far gone to repair, runs £900–£1,600 or more per window depending on size and whether it's single or double glazed with slimline units. Secondary glazing behind an original sash, rather than replacing the sash itself, is priced separately and covered in detail on our <a href='/eco-retrofit-refurbishment-london'>eco retrofit and secondary glazing page</a>, but broadly runs £350–£600 per window supplied and fitted. On the internal joinery side, a standard flush internal door supplied and fitted, including lining and architrave, is roughly £250–£450 in London, rising to £350–£650 for a period-matched four-panel door built or sourced to suit a Victorian or Edwardian house. Staircase repair for loose treads, squeaking, worn nosings or a wobbly handrail is typically £500–£2,500 depending on how much of the staircase needs attention, while a full staircase replacement on a standard straight or dog-leg stair runs £1,500–£4,000, more for a bespoke or open-tread design.
How Long Sash Window and Joinery Work Takes
Draught-proofing a single sash window, once a sash is out of the frame, routing the brush channel and re-hanging, is typically a half-day to a full day's work per window, so a terrace with 8-10 windows is usually a job of several days rather than weeks. A fuller restoration with cord replacement, re-puttying and repainting takes longer because putty needs several days to skin over before it can be painted, so a sash taken out, restored and reinstalled properly is realistically a week's job per window if you include drying time, even though the hands-on labour is a fraction of that. Splicing rotten timber into a sill or bottom rail adds time for the timber to be cut, glued and left to cure before it's shaped and painted. A single internal door, lining and architrave is typically a one-day fit once the door and lining are on site, longer where an opening in an old house is out of square and needs packing or adjusting to take a standard-sized lining. Staircase repairs from underneath, resecuring treads, wedges and glue blocks, are usually a one to two day job; a full staircase replacement typically takes two to four days including removing the old stair, fitting the new one and making good the surrounding plaster and skirting, though the stair itself is often out of use for at least part of that time, which needs planning around if it's the only way to the upper floor.
Building Regulations, Planning and Conservation Rules
Like-for-like sash window repair, and draught-proofing, don't generally trigger planning permission or Building Regulations, because you're not creating a new opening or materially altering the external appearance of the house. Full replacement of a sash window is a different matter on a freehold house not in a conservation area, permitted development rights usually allow like-for-like replacement without planning permission, provided the size and character of the opening doesn't change, but a flat has no permitted development rights of its own, so replacing windows in a converted Victorian house split into flats generally needs planning permission regardless of what the material is. Conservation areas add another layer: many London boroughs apply Article 4 directions specifically removing permitted development rights for windows on street-facing elevations, meaning even a straightforward timber-for-timber replacement can need planning permission, and a like-for-like timber sash with standard double glazing is often refused where it would visibly alter the glazing bar pattern or sightlines from the street. Slimline double glazing units, thin enough to fit the original timber rebate without altering the frame's profile, have a better track record of approval in conservation areas than standard double glazing, but every borough's conservation officer assesses this case by case, so it's worth checking with the local planning authority, or asking us to check on your behalf, before committing to a replacement sash rather than assuming a timber unit will automatically be approved. A staircase replacement that alters the pitch, going or rise of the stair, or changes the escape route from an upper floor, does fall under Building Regulations Approved Document K, and Building Control sign-off is needed; a like-for-like repair or refurbishment of an existing staircase generally doesn't.
Common Mistakes We Find in Previous Repairs
The single most common thing we find on a sash window that's been 'repaired' before is a synthetic cord or, worse, a length of nylon rope substituted for proper waxed sash cord, which stretches under the weight of the counterweight within a year or two and leaves the sash dropping again. Surface-mounted foam or brush strips stuck to the face of the staff bead rather than routed into a proper channel are another repeat finding, they look like draught-proofing but get painted over or peel off within a season and stop sealing properly. We also regularly find a sash simply painted shut rather than eased, which isn't a repair at all, and sills that have been patched with exterior filler rather than spliced with new timber, which looks fine for a year or two before the filler cracks and lets water straight back into the same spot. On the joinery side, the most common issue on staircases is a previous repair that's screwed straight down through the top of a tread into the riser below to stop a squeak, which usually doesn't address the actual cause, a loose wedge or glue block underneath, and just adds another failure point without fixing the movement that caused the squeak in the first place.
Repair, Restore or Replace: A Decision Framework
The starting question for any sash window is whether the failure is mechanical, cords, paint build-up, seized pulleys, all of which are straightforward and cheap to fix, or structural, meaning rot has actually eaten into the sill, bottom rail or box itself. A simple probe with a bradawl into the end grain of the sill and bottom rail tells you which category you're in before any money is spent. Where rot is confined to a section that can be cut out and spliced, repair is almost always cheaper than replacement and keeps the original glazing bar pattern and glass, which often has slight historic waviness that's part of the character of an older house. Where rot has spread through most of the box or the frame has genuinely failed structurally, a bespoke like-for-like replacement sash is the sensible option, and on a conservation area property it's usually the only option planning will approve anyway. Draught-proofing an otherwise sound sash is nearly always worth doing regardless of whether you restore fully now, because it's the cheapest single measure with the fastest payback in reduced heating bills of anything on this page. Where the real complaint is noise or heat loss rather than the sash's condition, secondary glazing behind a perfectly sound original sash, detailed on our <a href='/eco-retrofit-refurbishment-london'>eco retrofit page</a>, usually solves that without touching the original window at all.
Sash Windows vs Casement and uPVC Replacement
It's worth being clear that sash window repair and restoration is a different job from replacing a window with a modern uPVC or aluminium casement, both in what's involved and in what's likely to be approved. A sash window opens by sliding vertically on cords and weights, has glazing bars dividing the glass into panes on many Victorian and Edwardian houses, and is generally expected by conservation officers to be repaired or like-for-like replaced in timber rather than swapped for a different window type. A uPVC casement replacement is a straightforward like-for-like product swap on a house without conservation constraints, but installing one in place of an original timber sash on a conservation area elevation is one of the more common reasons we see planning enforcement action taken against homeowners who didn't check first, sometimes years after the window went in, when a neighbour complains or the council does an area review. If you're weighing up a full window replacement across a whole house rather than repairing individual sashes, it's worth getting that scoped as part of a wider refurbishment rather than window by window, since access, scaffolding and painting can often be shared across the job.
Leasehold Flats, Freeholder Consent and Shared Frontages
In a converted Victorian or Edwardian house split into flats, the sash windows on the front elevation are usually part of the building's shared external fabric even though only one flat looks out through them, which means most leases require freeholder consent before any window is repaired, restored or replaced, not just planning permission from the council. Where the freeholder has already agreed a house style, a specific paint colour, glazing bar pattern or even an approved joiner, it's worth checking that before commissioning separate work flat by flat, because mismatched sashes across a single converted house frontage is a common source of disputes between leaseholders. Where several flats in the same building need sash window work at a similar time, it's usually more cost-effective, and easier to get consistent freeholder sign-off, to coordinate the work across the building rather than each leaseholder instructing separately. Staircases in shared parts of a converted building, the common stair serving multiple flats rather than a stair inside a single flat, are typically the freeholder's responsibility and repair or replacement there needs to go through the building's management arrangements rather than being commissioned by an individual leaseholder.
Why Sequencing Matters on a Combined Job
Where sash window and internal joinery work happens alongside a wider refurbishment, the order of operations affects both cost and finish quality. Sash windows are best restored or replaced before internal decoration, since re-puttying, sanding and painting a sash inevitably sheds dust and drips into the room below it. Staircase repair or replacement is worth doing before final flooring and decoration are fitted around it, since access for materials and disposal of an old stair is far easier before carpets or floor finishes are down, and any plaster making good around a new stringer needs to happen before the walls are painted. Internal doors are best hung after flooring is laid but before final decoration, since a door has to be trimmed to the actual finished floor height, and painting the door and frame after hanging gives a cleaner line than painting first and risking chips during fitting. Skirting and picture rail matching should follow wall plastering and precede final decoration for the same reason. Treating sash windows, staircases and internal joinery as a single sequenced programme rather than separate call-outs booked in whatever order a homeowner happens to think of them usually saves both time and a second round of touch-up painting.