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Sash windows are commonly found on Georgian or Victorian houses and date back to at least the 1670s
Howard MustoeEnergy EditorSunday 23 November 2025 17:23 GMTComments
open image in gallerySash windows are often prized for their looks, but they cost more than standard casement windows due to their more complex engineering. (Pexels/@larissafarber)If you’re comparing quotes from the best window installers, you’ll quickly spot that sash windows tend to cost more than other styles. And if you’re not entirely sure what makes a window a “sash”, you’re in good company. This traditional design has its own quirks, influencing how the windows operate, how much the windows cost, and even how you clean or maintain them.
Sash windows, which slide vertically rather than opening outwards, are a hallmark of Georgian and Victorian architecture and have been used in British homes since at least the 1670s. They’re especially common in conservation areas, where planning rules often require like-for-like replacements to preserve a property’s original character. Their design also plays a major role in how well they retain heat, which is something we explore in depth in our guide on Are sash windows energy efficient?
In this guide, we explain why sash windows typically command a higher price than standard casement designs and whether they offer good value, supported by insight from a specialist sash-window installer. First, here’s how sash windows work.
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What are sash windows?
A sash in a window is the frame that holds the glass panes in place. In sash windows, there are usually two sashes that slide vertically past each other within the frame. Each sash can move independently to allow for ventilation.
How much do sash windows cost?
The average cost of replacement of a sash window is £1,300, according to our survey of suppliers, with wood frames costing more and uPVC being cheaper.
In London, you will pay more, with prices ranging from £2,500 to £5,000 per window for wooden frames and double glazing. If you are having multiple windows replaced at once, you can often negotiate a lower price per window because travel and setup costs are reduced.
Repairs can range from £80 to just under £500 to restore the look of the frame, repair the cord, or draught-proof the window, depending on how much work needs to be done.
If you have a row of sash windows and don’t insist on opening all of them, then you can save on repairs by sealing some shut.
Why do sash windows cost more?
Tom Coles, managing director of Mitchell & Dickinson, a company which makes period homes warmer and restores sash windows, said: “A sliding sash window has many more components than a casement window. The sashes themselves are carefully positioned so that they run past each other. There’s more manufacturing work to do, there's more components, and they need to be set really carefully so that they function perfectly.”
Sash windows usually have two sliding panels, called sashes. Each sash holds a sheet of glass divided by glazing bars to create the look of multiple small panes.
To keep the sashes from moving on their own, they are counterbalanced by weights fitted inside the window frames, connected by ropes.
open image in gallerySash windows are often seen on period homes (Pexels/@emilie-smerakova-750012491)This slightly more mechanically complex arrangement makes them more expensive to make and to fit. To work well, they need to fit closely in their frames to prevent draughts while still moving freely — engineering that adds further to the cost.
Traditionally, they are made of wood, which creates further challenges, since it is a comparatively expensive building material and it can also expand or contract with temperature changes and damp.
Newer models can be made of uPVC plastic, which is cheaper and does not rot or expand. Aluminium sash windows are also an option but with fewer suppliers and models available.
Aluminium, wood, and uPVC windows can be single, double or triple-glazed.
Another reason for the expense is a lack of standardisation. Many Victorian properties will have fairly uniform 4-foot-wide windows. But they were not factory-made and can often vary slightly in size, meaning that each window will require a degree of customisation to make sure it fits, adding to the cost.
How do sash windows work?
Sash windows work by using a system of cords and counterweights hidden within the frame. These weights balance the sashes, making them easy to lift and hold in position. Some modern versions use springs instead of weights.
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Are sash windows draughty?
Older sash windows can become draughty over time if the seals wear out or the timber shrinks. However, many modern sash windows include draught-proofing strips and double glazing to keep homes warm and energy efficient.
How to open sash windows safely
To open a sash window, unlock it first. Then, hold the bottom sash on each side and gently lift it upwards. For ventilation, you can also lower the top sash slightly while raising the bottom sash, which creates airflow around the room.
How to clean and paint sash windows
To clean sash windows, tilt or lift the sashes to access both sides of the glass. Use a gentle cleaner and a soft cloth to avoid damaging the frames. If you need to paint them, remove any old flaking paint, sand the surface lightly, and use a specialist wood paint for a lasting finish.
What is the difference between casement and sash windows?
Casement and sash windows are two of the most common styles in UK homes, but they work in very different ways, and those differences affect cost, ventilation, maintenance and suitability for certain properties.
Casement windows
Casement windows are the modern standard. They’re hinged at the side or top and open outwards like a door. Because they have fewer moving parts and a simpler frame, they tend to be cheaper to manufacture and install. Casements also offer excellent ventilation and energy efficiency, making them a popular choice for new builds and retrofits.
Sash windows
Sash windows, by contrast, feature one or two moveable panels (“sashes”) that slide vertically within the frame. This gives them their distinctive period look, often associated with Georgian and Victorian homes. The sliding mechanism – traditionally using weights and pulleys, though modern versions may use springs – is more complex than a casement hinge, which is one of the reasons sash windows are more expensive. They’re also commonly required in conservation areas where maintaining the building’s original appearance is essential.
Key differences at a glance
- Opening style: casement windows swing outwards; sash windows slide up and down.
- Cost: casement windows are generally cheaper due to simpler hardware and construction.
- Aesthetic: sash windows suit period properties; casements have a more modern look.
- Maintenance: sashes can be trickier to clean and repaint, especially older timber models.
- Regulations: conservation areas often require sash replacements to preserve traditional character.
If you’re replacing windows across your property, understanding these differences will help you decide which style fits your home, budget and local planning rules.
What are the pros and cons of sash windows?
Sash windows remain popular for their classic appearance and heritage value, but they’re not the right fit for every home. Here are the main advantages and drawbacks to consider before investing.
Pros of sash windows
Authentic period styleSash windows are a defining feature of Georgian, Victorian and Edwardian architecture. If you live in a period property, they help maintain the home’s original character and can even enhance kerb appeal.
Suitable for conservation areasIn many conservation zones, homeowners are required to replace existing sashes with like-for-like designs. Modern sash windows allow you to meet planning rules while benefiting from updated materials and improved energy performance.
Smooth, space-saving operationBecause the sashes slide vertically, they don’t open outwards into a garden, balcony or walkway. This makes them practical for tight exterior spaces where casement windows might be obstructed.
Improved modern performanceWhile older timber sashes are sometimes associated with draughts, today’s versions can achieve strong thermal efficiency. Double or triple glazing, brush seals and insulated frames all help reduce heat loss.
Cons of sash windows
Higher costSash windows are typically more expensive than casement windows. The sliding mechanism, counterweights or spring balances, and more intricate joinery all add to manufacturing and installation costs.
More maintenanceTraditional timber sashes require regular painting and upkeep to prevent swelling or rot. Even modern uPVC or aluminium models have more moving parts than a standard casement, which can mean additional maintenance over time.
Harder to clean Depending on the design, cleaning the exterior panes, especially on upper floors, can be more awkward than with casement windows that swing fully open.
Potential for draughts in older modelsOriginal sash windows without modern seals can let in air and reduce energy efficiency. Retrofits like secondary glazing or draught-proofing can help, but add to the overall expense.
Are sash windows worth it?
In short, sash windows are considered by many to be prettier. However, they are more expensive to make and maintain because they are more complicated and nonstandard compared to a hinged casement window.
Mr Coles said: “Sash windows are a real piece of Britain's architectural heritage. They were designed so that you could drop the top sash down and pull the bottom sash up slightly, and it creates air flow around the window. It was a clever bit of Victorian and Georgian engineering.”
“They've definitely got their place, and of course they're kind of beautiful to look at and beautiful to operate.”
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