Window replacement cost: uPVC, timber and aluminium compared
2026 prices per window and for a whole house in uPVC, aluminium and timber, the extras a quote can leave out, and the certificate and planning rules in each UK nation.
Replacing a standard uPVC casement window costs £400 to £900 supplied and fitted in 2026, and replacing every window in a 3-bed house costs £4,000 to £9,000. The frame material moves the price most, with aluminium and timber costing around double. We give prices per window by material, style and size, whole-house totals, the extras a quote can leave out, and the certificate and planning rules in each UK nation.
Window replacement cost per window
These are 2026 prices for one standard double-glazed window, bought alone and supplied and fitted. A casement is the side-hung or top-hung type most UK homes have. Work on an existing home is normally charged VAT at 20%, and not every price list says whether it is included, so ask.
| Frame | Supply only | Supplied and fitted |
|---|---|---|
| uPVC casement | £250 – £450 | £400 – £900 |
| uPVC sliding sash | £350 – £650 | £700 – £1,400 |
| Aluminium casement | £600 – £1,000 | £700 – £1,600 |
| Timber casement | £700 – £1,200 | £1,000 – £2,500 |
uPVC windows cost
uPVC is the cheapest frame and the one most replacement windows are made from. White is the base price. A woodgrain foil adds £30 to £80 a window, and a custom colour or a frame in a different colour on each side adds 10% to 15%.
Aluminium windows cost
Aluminium costs £700 to £1,600 a window fitted. The frames are slimmer for the same strength, so more of the opening is glass, and frame guarantees of 25 years are offered on aluminium.
Timber windows cost
Timber is the dearest frame at £1,000 to £2,500 a window fitted, with bespoke joinery at the top of the range. On a period house in a conservation area, the council may want the new windows to match the originals' profile, glazing pattern and colour, which a standard uPVC casement may not do.
Cost by window style
Casements are the baseline. Sliding sash, bay and bow windows cost more because the frame is more complex or there are more panes in one opening.
| Style | Supplied and fitted | What the price covers |
|---|---|---|
| Sliding sash, uPVC | £700 – £1,400 | One sash window with a heritage look |
| Bay, uPVC | £1,500 – £4,500 | 3 panes on a typical semi, more on a larger bay |
| Bow | £1,800 – £4,500 | 4 or 5 panes on a curve |
| Bay or bow, aluminium | £3,500 – £6,000 | Larger frames in a dearer material |
A bay is priced as one unit but is three or more windows joined on posts, which is why it costs several times a casement. Replacing an existing bay is ordinary window work. Adding a bay where there was none is treated as an extension for planning in England and may need permission.
Window prices by size
Size moves the price far less than material. Going from a 600 x 900mm uPVC window to a 1,800 x 1,200mm one quadruples the glass but adds only £350 to £550 to the fitted price.
| Size (width x height) | Supply only | Supplied and fitted |
|---|---|---|
| 600 x 900mm | £200 – £350 | £450 – £650 |
| 1,000 x 1,000mm | £250 – £400 | £500 – £750 |
| 1,200 x 1,200mm | £300 – £450 | £550 – £850 |
| 1,500 x 1,200mm | £350 – £500 | £650 – £950 |
| 1,800 x 1,200mm | £450 – £650 | £800 – £1,200 |
Cost to replace all the windows in a house
Whole-house prices follow the number of windows, not the floor area. These are uPVC totals, supplied and fitted.
| Home | Typical windows | uPVC, supplied and fitted |
|---|---|---|
| Flat | 4 – 6 | £2,000 – £4,500 |
| 2-bed house | 6 – 8 | £3,500 – £6,000 |
| 3-bed house | 8 – 12 | £4,000 – £9,000 |
| 4-bed house | 12 – 16 | £6,500 – £14,000 |
| 5-bed house | 18 – 25 | £10,000 – £20,000 |
A typical 3-bed semi in white uPVC lands at £5,000 to £7,500. In aluminium, a 4-bed house costs £12,500 to £25,000 and a 5-bed £18,000 to £40,000 or more.
| Frame | 3-bed house, 8 to 12 windows |
|---|---|
| uPVC | £4,000 – £9,000 |
| uPVC sliding sash | £6,000 – £10,000 |
| Aluminium | £8,000 – £16,000 |
| Timber | £9,000 – £16,000 |
Costs a window quote can leave out
A low quote is often a quote with lines missing. These are the extras that come up most, priced per window or per job.
| Extra | Typical cost | When it applies |
|---|---|---|
| Scaffolding | £300 – £800 per job | Upper windows that need it |
| Making good plaster and paint | £50 – £150 per window | Around each new frame |
| New internal sills | £30 – £80 per window | Where the old sills are replaced |
| Woodgrain foil | £30 – £80 per window | Instead of plain white uPVC |
| Custom or dual colour | 10% – 15% more | Any colour outside the standard range |
| Security hardware | £50 – £100 per opening | Upgraded locks on ground floor windows |
| Triple glazing | 15% – 30% more per window | Instead of double glazing |
| Acoustic glass | 10% – 15% more | Where noise is the problem |
If the windows are part of a whole-house renovation budget, fit them before the plastering and decorating. The making good around each frame then folds into work you are paying for anyway.
Double or triple glazing
Double glazing is the standard in 2026, and every price above assumes it. Triple glazing adds 15% to 30% to each window. On most UK homes the lower heat loss takes 15 to 25 years to pay that back, so buy it for warmth and quiet rather than as a saving.
Modern uPVC and aluminium windows reach an A or A+ energy rating as standard, and some uPVC frames reach a U-value, the measure of heat lost through glass and frame, as low as 1.0 W/m²K. Choosing A+ over C-rated windows across a whole house adds only £200 to £500.
Building regulations and FENSA certificates
In England, building regulations have applied to all replacement glazing since 1 April 2002. A replacement window is a controlled fitting, so the work needs approval one of two ways: from an installer registered with a competent person scheme, or through a building control application to the council.
FENSA and CERTASS are two of those schemes. A registered installer's work is self-certified under building regulations, and the certificate should reach you within 8 weeks of completion. Keep it with the house papers, because a buyer's solicitor will ask for it.
The new windows have to meet these rules:
- Heat loss. Glass and frame together must meet a U-value limit, the measure of how much heat passes through.
- Safety glass. Any pane within 800mm of the floor, any glazed door up to 1,500mm, and any side panel within 300mm of a door up to 1,500mm needs safety glass.
- Escape windows. A window that serves as a fire escape needs an opening of at least 0.33m², no side under 450mm, and a bottom edge no more than 1,100mm above the floor.
- Ventilation. If the old windows had trickle vents, the new ones need them too, no smaller and adjustable. If they had none, the room must be no worse ventilated afterwards.
New frames make a house more airtight, and a room that loses its background ventilation is where condensation on cold walls and glass starts.
Do new windows need planning permission?
In England, replacing windows is permitted development, with no planning application, as long as the new windows are similar in appearance to the originals. The exceptions:
- New bay windows count as an extension and may need permission.
- Upper-floor side windows must be obscure-glazed and either fixed shut or with the opening part more than 1.7m above the floor.
- Listed buildings need listed building consent for any significant work, inside or out.
- Conservation areas, national parks and areas of outstanding natural beauty may carry extra restrictions.
- Article 4 directions let a council withdraw permitted development rights, so ask the council before ordering if one covers your street.
Where the council expects windows that match the originals' profile, glazing pattern and colour, as it may in a conservation area or on a listed building, budget 20% to 30% more for the windows.
Window rules in Scotland, Wales and Northern Ireland
In Scotland, replacing a window including its frame needs no building warrant: it is type 20 in schedule 3 of the Scottish building regulations. The work must still comply. A complete replacement is not a repair, so the new window has to meet the full current standards rather than simply match the old one.
| Nation | What replacement windows need |
|---|---|
| England | A competent person scheme certificate, or council building control approval |
| Scotland | No building warrant, but the full current building standards apply |
| Wales | Welsh Approved Documents and Welsh planning rules |
| Northern Ireland | Northern Ireland's own building regulations and planning system |
Wales has its own Approved Documents and has run its own planning system since 2016, so the England rules above may not match. Northern Ireland runs separate planning and building control. In both, ask the installer which standard the windows are certified to before you pay a deposit.
Window replacement costs by region
The prices here are UK-wide. Replacing windows in London and the South East costs about 10% to 20% more than the national average, because installation labour costs more there.
In the Thames Valley, for example, 8 to 10 uPVC windows cost £5,500 to £12,000 including VAT, against £4,000 to £9,000 for a 3-bed house nationally.
How long window replacement takes
A whole house of windows takes 2 to 5 days on site. Each window runs through the same steps:
- The old window is taken out and its frame cut free of the wall.
- The opening is cleaned, and the new frame is fixed, levelled and packed.
- The glass goes in, and the gap around the frame is sealed inside and out.
- Trims, sills and trickle vents go on, and the window is checked to open, close and lock.
Before the final payment, go round every window with a snagging list: each one opens, closes and locks, and the seals and trims are unbroken. Ask the installer for the date the certificate will arrive.
Is it worth replacing 20-year-old windows?
Most windows last 20 to 30 years, so a 20-year-old window is not due for replacement on age alone. The frame decides it. Replace the window when:
- The frame is rotten, cracked or warped, and the window no longer closes tight.
- Draughts come through with the window shut and locked.
- The house still has single glazing.
- Several windows have failed seals and the frames are worn as well.
Misted double glazing on its own is a failed seal in the glass unit, not a failed window, and a sound frame can take a new glass unit.
Grants for new windows in 2026
There is no general government grant for replacement windows in 2026. ECO4, the Energy Company Obligation, can cover glazing for some low-income households on qualifying benefits in England, Scotland and Wales, but it mainly funds heating and insulation.
ECO4 has been extended to 31 December 2026, and no supplier scheme follows it. Northern Ireland sits outside ECO4.
Common questions
How much does it cost to replace an existing window?
Replacing one standard uPVC casement window costs £400 to £900 supplied and fitted in 2026. Aluminium costs £700 to £1,600 and timber £1,000 to £2,500. Scaffolding adds £300 to £800 to a job that needs it, and making good around the frame adds £50 to £150.
What is the average cost of new windows for a 3-bed house in the UK?
New windows for a 3-bed house cost £4,000 to £9,000 in uPVC, for 8 to 12 windows supplied and fitted. A typical white uPVC semi comes in at £5,000 to £7,500. The same house costs £8,000 to £16,000 in aluminium and £9,000 to £16,000 in timber.
How much does it cost to replace windows in a 2-bedroom house?
Replacing the 6 to 8 windows in a 2-bed house costs £3,500 to £6,000 in uPVC, supplied and fitted. A flat with 4 to 6 windows costs £2,000 to £4,500. Bays, sashes and upper windows that need scaffolding push the total up.
How much are new windows for a 4-bed house?
A 4-bed house with 12 to 16 windows costs £6,500 to £14,000 in uPVC and £12,500 to £25,000 in aluminium, supplied and fitted. A 5-bed house with 18 to 25 windows costs £10,000 to £20,000 in uPVC.
How much does a wooden window cost to replace?
A timber window costs £1,000 to £2,500 supplied and fitted, which makes it the dearest frame. The window alone costs £700 to £1,200 before fitting. Where a conservation area or listed building needs a close match to the original, budget 20% to 30% more.
How much does double glazing cost?
Double glazing costs £400 to £900 per window in uPVC, supplied and fitted, and it is the standard in 2026. A whole 3-bed house costs £4,000 to £9,000. Triple glazing adds 15% to 30% per window and takes 15 to 25 years to pay back on most homes.
Is it worth replacing 20 year old windows?
A 20-year-old window is worth replacing when its frame has failed, not because of its age. Most windows last 20 to 30 years. Replace a frame that is rotten, warped or draughty when locked; a misted pane in a sound frame is a glass fault.
Can I get a grant for new windows?
There is no general government grant for new windows in 2026. ECO4 can fund glazing for some low-income households on qualifying benefits in England, Scotland and Wales, and it ends on 31 December 2026. Northern Ireland is not covered by ECO4.
Do I need a FENSA certificate for new windows?
In England, replacement windows need either a certificate from a FENSA or other competent person scheme installer, or building control approval from the council. The certificate should arrive within 8 weeks of completion. Without either, you have no proof of compliance to give a buyer's solicitor.
Do replacement windows need planning permission?
Replacement windows that look similar to the originals need no planning permission in England. A listed building needs listed building consent, a new bay window may need permission as an extension, and a conservation area or Article 4 direction can add restrictions.