Windows & doors
Sash Windows
Sash windows are windows with one or more panels, called sashes, that slide vertically in a frame, traditionally balanced by hidden weights or modern springs. They are replaced or upgraded when period sashes have rotted, rattle, stick or leak heat, and owners want the traditional look with double glazing and better security.
- Guide from £1,495
- Free survey
- Written quote
- UK-wide
- Free survey for new glazingMeasured on site before anything is made
- Written quoteThe price is fixed for the specification shown
- Every glazing jobGlass, windows, doors and commercial
- UK-wide coverEngland, Wales, Scotland and Northern Ireland
- Guarantee terms in writingSet out with every quote

How our sash windows service works
We survey, supply and fit sliding sash windows for period houses, flats and conversions across the UK, in timber or uPVC. A glazier measures each opening, records the existing joinery details such as horns, glazing bars and mouldings, and checks the condition of the box frame and sill. We then advise whether full replacement, new sashes in the existing box, or another approach suits the property and its planning status. You receive a written quote that fixes the price for that specification. Windows are made to order, and on fitting day our glaziers remove the old sashes or frames, install the new windows, seal and finish them. Building regulations apply across the UK, with different detail in each nation.
What's included
- Survey recording mouldings, horns, bars and box condition
- Made-to-measure timber or uPVC sash windows
- Double glazed units, with safety glass where required
- Removal of old sashes or frames and disposal
- Weights or balances set for smooth, even sliding
- Sealing, finishing and written guarantee terms
When you might need sash windows
- Sashes rattle in the wind or let in cold draughts
- Bottom rails or sills are soft, split or rotting
- Sashes stick, drop or need propping open
- Broken cords mean sashes cannot be lifted safely
- Single glazed sashes stream with condensation each winter
Guide prices
| Typical job | Guide price inc VAT |
|---|---|
| uPVC sliding sash, 900 × 1500 mm | £1,495 – £1,995 |
| Timber-effect uPVC sash, 900 × 1500 mm | £1,795 – £2,295 |
| Painted timber sash, 900 × 1500 mm | £2,595 – £3,295 |
Options to choose between
Timber box sash
Traditional weights, cords and pulleys in a box frame, made in engineered softwood or hardwood and factory painted to your colour.
Spring-balanced timber sash
Timber sashes running on concealed spring balances, giving a slimmer frame where weight pockets are not needed or space is tight.
uPVC sliding sash
Low-maintenance uPVC frames with sculpted profiles and optional woodgrain foils, suited to homes where planning rules allow uPVC.
Replacement sashes only
New double glazed sashes fitted into your existing sound box frame, keeping original linings, architraves and plasterwork.
Glazing bar patterns
Two over two, six over six or other bar layouts, as true divisions or bars bonded to the glass faces.
Heritage glass options
Slim double glazing, low-E coatings and textured glass that looks like old cylinder glass for sensitive elevations.
Tilt-in sashes
Sashes that tilt inwards for cleaning upper-floor glass from inside, and can help provide an escape opening.
Good to know about sash windows
A traditional box sash hides cast-iron or lead weights inside the side boxes of the frame, connected to each sash by cords running over pulleys. Modern sash windows often use spiral or spring balances instead, which take up less depth and suit uPVC and some new timber designs without weight pockets.
Sash windows can be supplied as complete new frames, or as new double glazed sashes fitted into an existing sound box frame. Keeping the box retains original linings and architraves and reduces disturbance to plaster, but only works when the frame is free of rot and still square.
Timber sash windows are usually made from engineered softwood or durable hardwoods, factory primed and finished with microporous paint that lets moisture escape. Factory finishing gives a more even coat than painting on site, but timber still needs periodic redecoration, and the interval depends on exposure and colour.
Heavy double glazed sashes need matching weights. When single glazed sashes are swapped for double glazed ones in an existing box, the old weights are usually too light, so the glazier re-weighs each sash to stop it dropping or creeping up, and checks the pulleys can carry the load.
In England, Approved Document L allows an alternative where a window must keep a building's character: a centre-pane U-value no worse than 1.2 W/m²K, or single glazing supplemented by low-E secondary glazing. Otherwise a replacement should meet 1.4 W/m²K or Window Energy Rating band B.
Slim double glazed units let sash windows keep fine glazing bars and traditional proportions while improving thermal performance. Bars can be true divisions with individual units, or bars bonded to both faces of a single unit with a spacer bar between the panes, which looks very similar from a short distance.
Many Victorian and Georgian sashes reach low to the floor. In England, Approved Document K treats glazing within 800mm of floor level as a critical location, so the lower panes of tall sash windows usually need toughened or laminated safety glass, which should be permanently marked.
A sliding sash only opens to about half its frame height, which can make an escape window harder to achieve. In England, Approved Document B guidance calls for at least 0.33 m² clear opening, 450mm high and wide, so tilt-in or side-hung escape sashes are sometimes specified for upper floors.
Security on sash windows comes from keyed sash locks at the meeting rails, sash stops that limit the opening for ventilation and child safety, laminated glass, and close-fitting staff and parting beads. Ground-floor sashes in older houses are often the weakest point, so locks are worth upgrading during replacement.
Sash window prices depend on size, timber or uPVC, whether you replace the whole frame or just the sashes, the glazing bar pattern, horns and mouldings, glass type and the paint colour. Listed or conservation work that needs matching details costs more. See the guide prices for typical ranges.
Trickle vents can be fitted discreetly in the head of a sash frame or the top rail. In England, Approved Document F expects ventilation after window replacement to be no worse than before, although listed buildings and conservation areas may meet it only where reasonably practicable, agreed with building control.
Sash windows that run smoothly need routine care: keep the pulley wheels free of paint, wax or lightly lubricate the running channels, check the cords for fraying, and repaint timber before bare wood shows. Draught brush seals in the beads and meeting rails reduce rattles and heat loss.
Rules and regulations
Building regulations differ between the four UK nations. Here is what usually applies to sash windows; your written quote confirms the detail for your property.
England
Approved Document K requires safety glass in critical locations in England: glazing in doors and in side panels within 300 mm of a door, up to 1500 mm above floor level, and any glazing in walls or partitions up to 800 mm above floor level.
Approved Document L sets the minimum energy performance for replacement windows and doors in existing homes in England: a U-value of 1.4 W/m²K, or Window Energy Rating band B for windows; doors can instead meet a Door Set Energy Rating (band B, or band C for doors more than 60% glazed); rooflights need 2.2 W/m²K.
In England, replacing a whole window, roof window or glazed external door is building work. It has to be notified to building control, either by an installer registered with a competent person scheme such as FENSA or Certass, or through a building notice to the council. Replacing only the glass in an existing frame is a repair and is not notifiable.
Wales
In Wales, Approved Document N covers safety glazing: safety glass is needed in and around doors and in low-level glazing where people could walk into it.
Wales sets its own energy standards in the Welsh Approved Document L. Replacement windows, doors and rooflights must meet the limiting values set there, which your quote will reference.
In Wales, replacing a whole window or glazed external door is building work and is notified either by an installer registered with a competent person scheme or through the local authority's building control. Replacing only the glass in an existing frame is treated as a repair.
Scotland
Section 4 (Safety) of the Scottish Technical Handbooks covers glazing that people could collide with, such as glass in and beside doors and low-level glazing, where safety glass is needed.
Section 6 (Energy) of the Scottish Technical Handbooks sets the thermal performance that replacement windows, doors and rooflights should achieve.
In Scotland, replacing windows or doors in a house like for like does not usually need a building warrant, but the work must still meet the building standards in the Technical Handbooks. Flats and listed buildings can differ, so check with the local authority.
Northern Ireland
Technical Booklet V covers safety glazing in Northern Ireland, including glass in and around doors and low-level glazing where people could walk into it.
Technical Booklet F1 sets the energy performance that replacement windows, doors and rooflights need to meet in Northern Ireland.
In Northern Ireland, replacing windows and doors in an existing home does not usually need a building control application, but the work must still meet the Building Regulations (Northern Ireland), including the energy and safety glazing requirements. Other buildings, new openings and structural changes can need approval, so check with the council's building control if you are unsure. Replacing only the glass in an existing frame is a repair.
What happens next
Tell us about the job
Use the quote form, call, WhatsApp or live chat. Photos and rough sizes help.
Survey and measure
A glazier visits, checks the opening and measures. For simple glass swaps this is often done on the same visit as fitting.
Written quote
You get a written quote with the specification, price and guarantee terms. Nothing is ordered until you agree.
Made and fitted
Glass, frames or panels are made to size and fitted. We tidy up and take the old glass away.
Sash Windows questions
How much do sash windows cost?
The cost of sash windows depends on size, material, whether you replace the whole frame or only the sashes, the glazing bar pattern, the glass and the finishing details such as horns and mouldings. Timber usually costs more than uPVC, and listed building work costs more again. See the guide prices for typical ranges; the written quote fixes your price.
Can I have double glazed sash windows in a listed building?
Sometimes, but listed building consent is needed for significant works, and some councils will only accept repair of the original windows or slim double glazing with matching details. Secondary glazing is often accepted where new windows are not. Speak to your council's conservation officer before ordering; we can provide drawings and specifications to support an application.
Should I repair or replace my sash windows?
Repair suits sashes where the timber is mostly sound and only cords, beads or small sections need attention, especially in listed or conservation properties. Replacement suits frames with widespread rot, distortion or repeated failures, or where you want double glazing and better security. A survey of each window shows which approach makes sense, and we can quote either.
Are uPVC sash windows allowed in conservation areas?
It depends on the council. Some conservation areas and Article 4 directions require timber on front elevations, while others accept well-detailed uPVC sashes with sculpted profiles and run-through horns. Listed buildings almost always need timber. Check your council's guidance or ask the planning department before choosing uPVC, because removing unauthorised windows later is costly.
How long does it take to replace sash windows?
Fitting a single sash window usually takes most of a day, longer where the box frame is removed or plaster disturbed. A whole house typically takes several days on site. The windows are made to order first, and timber sashes with special details take longer to manufacture; the lead time is confirmed in writing with your quote.
Do sash windows have to meet building regulations?
Yes. Replacement windows are controlled under building regulations across the UK, and the detail differs between nations. In England, the work can be self-certified by an installer registered with a competent person scheme or approved by building control. Energy, ventilation, safety glazing and escape all apply, though listed buildings may meet some standards only where reasonably practicable.
Will double glazed sashes be too heavy for my existing frame?
Double glazed sashes are heavier than single glazed ones, so the box frame, pulleys and weights must cope. When new sashes go into an existing box, the glazier checks the pulleys and adds or replaces weights so each sash balances. If the box is weak or rotten, a new frame is the better option, and the survey will tell you.
How secure are sash windows?
New sash windows can be secure when fitted with keyed locks at the meeting rails, sash stops, laminated glass and tight-fitting beads. Older sashes often rely on a single catch, which is easily forced. Upgrading ground-floor and easily reached windows first makes sense, and the glazier can recommend locks that suit the sash and frame.
What maintenance do timber sash windows need?
Timber sash windows need periodic repainting, how often depends on exposure, orientation and colour, plus routine checks of cords, pulleys and seals. Keep paint off the running surfaces, clean the sills and touch up chips before water gets in. Factory-finished timber lasts longer between coats than site-painted joinery, but still benefits from yearly inspection.
What guarantee comes with new sash windows?
Manufacturer guarantees apply to the joinery, finish, sealed units and hardware, and the terms are confirmed in writing. Cover on the paint finish often depends on regular maintenance, so check the conditions. Guarantee terms for the installation are set out in writing with your quote, so you know what is covered before agreeing to go ahead.
Sash Windows near you
Choose your county or area for local details, towns we cover and the rules that apply where you live.
England
- Bedfordshire
- Berkshire
- Bristol
- Buckinghamshire
- Cambridgeshire
- Cheshire
- Cornwall
- County Durham
- Cumbria
- Derbyshire
- Devon
- Dorset
- East Riding of Yorkshire
- East Sussex
- Essex
- Gloucestershire
- Greater London
- Greater Manchester
- Hampshire
- Herefordshire
- Hertfordshire
- Isle of Wight
- Kent
- Lancashire
- Leicestershire
- Lincolnshire
- Merseyside
- Norfolk
- North Yorkshire
- Northamptonshire
- Northumberland
- Nottinghamshire
- Oxfordshire
- Rutland
- Shropshire
- Somerset
- South Yorkshire
- Staffordshire
- Suffolk
- Surrey
- Tyne and Wear
- Warwickshire
- West Midlands
- West Sussex
- West Yorkshire
- Wiltshire
- Worcestershire
Scotland
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