A sash window has one or two panels (sashes) that slide vertically within the frame, the traditional style of Victorian and Georgian homes. Modern versions carry slim double-glazed units that keep the period look while meeting today's energy rules. A fitted uPVC sash costs £700 to £1,500 in 2026, while timber heritage sashes cost more again. Price your own set in the sash window calculator.
How a sash window works
The classic box sash has two panels that slide past each other on cords and counterweights, or on modern spring balances. You can open the top and bottom together to draw cool air in low and push warm air out high, which is part of why they suit tall period rooms. The trade-off is more mechanism than a casement, which is why a sash costs more to make and fit. Compared with the simpler hinged style covered in our casement windows guide, a sash is the dearer but more authentic choice for an older home.
A well-made sash on a Victorian frontage is a thing of beauty, and it sells houses. But it is not a casement, and you pay for the extra engineering. Do not order sashes for a 1980s semi just because they look posh.
Tom Bradley, FENSA-registered installer
Sash window costs in 2026
Material drives the price, and with sashes the choice is usually between uPVC and timber. uPVC sashes give you the look and the energy performance at the lower price. Timber sashes cost more but are often the only option allowed on period and listed homes, and they reward the spend with a 30 to 60 year life if maintained.
| Material | Per window (fitted) | Notes |
|---|---|---|
| uPVC sash | £700–£1,500 | Period look at the lower price |
| Aluminium sash | £950–£2,030 | Less common; slim, durable |
| Timber sash | £1,330–£2,850 | Heritage and conservation homes |
Source: DGCC 2026 dataset, cross-checked against Checkatrade.
Period and conservation context
This is where sash windows demand care. If your home is in a conservation area or is listed, you usually cannot simply fit whatever you like. Planners often require timber sashes that match the original proportions, glazing bars and sightlines, and you may need consent before any work starts. Always check with your local planning authority first. Heritage replacements can also attract help: see the grants guide for the schemes that may apply, though most are income-based rather than tied to property age.
On a listed building, the conservation officer is your real customer. Get them on side before you order a single window, because if the sightlines are wrong they can make you take the whole lot out at your own cost.
Tom Bradley, FENSA-registered installer
The verdict on sash windows
It depends Sash windows are worth the premium when the house genuinely calls for them, on a Victorian terrace, a Georgian townhouse or anywhere the street and the planners expect vertical sliders. For a modern home, the casement is the better-value pick. If you are torn between the two styles, compare prices and looks against our casement windows guide, then price the job in the sash window calculator.
Frequently asked questions
A fitted uPVC sash window costs £700 to £1,500 in 2026. Timber sash windows for period and conservation-area homes cost more, typically £1,330 to £2,850, reflecting the heritage frame and finish.
A sash window has one or two panels, called sashes, that slide vertically within the frame rather than swinging open. It is the traditional window of Victorian and Georgian homes across the UK.
Yes. Modern uPVC and timber sash windows are made with slim double-glazed sealed units that keep the period proportions while meeting the Part L requirement of a U-value of 1.4 W/m²K or lower.
Often not. Conservation areas and listed buildings usually require timber sashes that match the originals, and may need consent for any change. Always check with your local planning authority before ordering.
Sash windows carry more mechanism (the sliding sashes, balances or cords and the box frame) than a simple hinged casement, so they cost more to make and fit. A uPVC sash runs £700 to £1,500 against £400 to £1,000 for a uPVC casement.
They need repainting every 8 to 10 years to protect the frame, plus occasional easing of the sashes. In return they can last 30 to 60 years and are often the only style permitted on period and listed homes.