A casement window is hinged at the side or top and opens outward on a handle. It is the default window in most UK homes for good reason: the sash presses tight against the frame seal when closed, so it insulates well, and the simple mechanism keeps it affordable. A fitted uPVC casement costs £400 to £1,000 in 2026, with around £650 typical. You can price your own set in the uPVC window calculator.
The questions homeowners actually have are rarely about what a casement is. They are about why one will not close, what a new hinge costs, whether a bedroom window is big enough to climb out of in a fire, whether trickle vents are compulsory, and whether the flush version is worth the premium. This guide answers those in turn, and the broader set of Double Glazing Questions Answered deals with the cost, grant and lifespan questions that sit outside a single style.
How does a casement window work?
The opening sash is hung on hinges down one side (a side-hung casement) or along the top (a top-hung or awning casement). Turn the handle and the sash swings outward, then the multipoint lock pulls it back hard against a compression seal to close. That compression is why casements seal so well and why they are easy to make weathertight. Fixed (non-opening) casement panes are cheaper still, because they have no mechanism at all.
The hinge itself is worth understanding, because it is the part that fails. On uPVC and aluminium casements the hinge is a friction stay: a pair of sliding steel arms in a track, one at the top of the sash and one at the bottom, with an adjustable friction pad that holds the window at whatever angle you leave it. There is no traditional knuckle hinge. When people say their window "has dropped" or "catches on the frame", the friction stay is almost always the culprit.
Side-hung or top-hung: which should you choose?
A side-hung casement is the default. It opens wide, gives the best airflow and is the easiest to climb out of, which matters for bedrooms. The drawback is that a wide-open sash catches the wind and, on a narrow window, the opening can still be too small to count as an escape route.
A top-hung (awning) casement hinges along its head and pushes out at the bottom. It sheds rain while open, so you can leave it ajar in a shower, and it is safer above a footpath. It is the usual choice for a toplight above a fixed pane, for bathrooms and for kitchen windows over a sink, and it will not normally serve as a fire escape opening.
Most real windows combine the two: a fixed pane for light, a side-hung opener for ventilation and escape, and sometimes a top-hung toplight above. Every opener adds hinges, a handle and a lock, so specify them where you need them rather than everywhere.
Nine out of ten houses I fit are casements, and there is a reason for that. The seal is excellent, the cost is sensible, and there is very little to go wrong over twenty-odd years. For most people it is simply the right answer.
Tom Bradley, window installer
Casement window costs in 2026
Material is the main driver. uPVC is the value choice, aluminium adds slim sightlines and durability for a premium, and timber is dearest of all and usually reserved for period or conservation-area homes, the kind that often suit a sliding sash instead, as our casement versus sash comparison sets out. You can price your own spec in the casement window calculator, and the table below is fully fitted, including removal, sealing and the certificate. These figures are cross-checked against Checkatrade cost data.
| Material | Per window (fitted) | Notes |
|---|---|---|
| uPVC casement | £400–£1,000 | Best value everyday choice |
| Aluminium casement | £540–£1,350 | Slim frames, long life |
| Timber casement | £760–£1,900 | Period and conservation homes |
Source: DGCC 2026 dataset, cross-checked against Checkatrade.
What does a casement cost by window size?
Material sets the bracket; size decides where in it you land. The Federation of Master Builders publishes fitted prices for the three standard uPVC casement sizes, current as of July 2026, and they sit comfortably inside our own range. Note how little the price moves as the window gets bigger: most of the cost is the visit and the labour, not the glass.
| Window size | uPVC casement (fitted) | What it usually is |
|---|---|---|
| 600 x 900 mm | £525 | Bathroom, landing, small bedroom |
| 900 x 1,200 mm | £615 | Standard bedroom window |
| 1,200 x 1,200 mm | £670 | Lounge or dining room window |
Source: Federation of Master Builders, UK window prices, July 2026.
That flatness is worth knowing before you take a quote. An installer who prices a small landing window at not much less than a large lounge window is pricing labour honestly, not overcharging. Push back instead on a quote that scales steeply with size, or one that will not itemise per window. Our guide to avoiding overcharging covers the tactics to watch for.
Which homes suit a casement window?
Best Buy Casements suit the great majority of UK homes: semis, terraces, bungalows, post-war housing and new builds. They give you clean lines, a good seal and a sensible price, which is why they are the standard recommendation here. If your home is modern or has had casements before, this is almost certainly the style to fit.
Are flush casements worth the extra?
It depends A flush casement closes level with its outer frame, so the face of the window is one flat plane. The everyday alternative, the stormproof casement, has the sash overlapping the frame by a few millimetres, leaving a visible step. Both seal against a compression gasket and both achieve the same thermal performance. The difference is entirely one of appearance, and the flush version costs roughly 30% more because the tolerances are tighter and the profile is harder to fabricate.
So the answer depends on the house. On a Victorian frontage, a stone cottage or a barn conversion, the flush profile is the difference between a job that looks right and one that looks merely done, and some conservation areas specify a flush or near-flush profile outright. On a post-war semi or a new build, you are paying a third more for a detail nobody will notice. Price both in the flush casement calculator before you decide.
One practical warning: ask each installer specifically whether they are quoting flush or stormproof. The two are easy to confuse on a written quotation and the price gap is large.
Why will my casement window not close properly?
This is the most common casement complaint by a distance, and it is rarely the window itself. Work through the causes in this order.
- The friction stay has worn or bent. Grit gets into the track, the pivot points wear, and the sash starts to sit fractionally low. You feel it as the handle needing a shove, or the bottom corner catching on the frame.
- The lock keeps have drifted. The cams on the locking bar engage into keeps screwed to the frame. Over years the fixings loosen and the keeps move a millimetre or two, which is enough to stop the handle turning fully.
- The compression seal has hardened. An old gasket goes stiff and takes a permanent set, so the window stops pulling in tight. You usually notice draughts and whistling first.
- Dirt in the hinge track. The most overlooked cause. Clean it out, then apply a little light oil to the pivot points. Checkatrade specifically advises against WD-40, because it dries out quickly and leaves the mechanism worse off than before.
- Seasonal movement. A timber casement swells in a wet winter and eases again in summer. Consistently seasonal sticking is the frame breathing, not a fault.
How long do casement hinges last, and what do new ones cost?
There is no published service life for a friction stay, and any figure claiming one is guesswork. What is reliable is that the hinge is the first part of a casement to fail and the cheapest to put right. According to Checkatrade, updated July 2026, the parts and labour break down as follows.
| Item | Unit | Cost |
|---|---|---|
| Replacement hinges (friction stays) | Per pair | £18–£37 |
| Fitter labour | Per hour | £25–£40 |
| One window, parts and labour | Per window | Around £60 |
| Five windows in one visit | Whole job | Around £250 |
Source: Checkatrade window hinge replacement cost guide, updated July 2026.
A pair takes one to two hours to change. Two things push that figure up: tilt-and-turn and fire escape hinges are specialist parts, and uPVC hinges are not universal, so the replacement must match the size, opening type and, on a flush casement, the frame profile. Replace both hinges even if only one has failed, so they wear evenly and the sash stays square. Set against £400 to £1,000 for a new window, around £60 to make a sound casement work again is money well spent.
Can you replace just the glass in a casement window?
Yes, and it is usually the right call. If the sealed unit has misted but the frame, hinges and locks are sound, a glazier can extract the failed unit and fit a new one for a fraction of the cost of a whole window. Misting you cannot wipe off means the edge seal has failed, which our guide to window condensation explains in full, and the repair cost calculator will give you a figure. The decision tips to full replacement once the frame has deteriorated, or once the window is far enough into its service life that you would be repairing one unit a year.
People write off perfectly good windows because the handle got stiff. I have turned up expecting to quote for a full replacement and left an hour later having fitted two hinges and adjusted the keeps. Always get someone to look at the hardware before you sign for a whole new set.
Tom Bradley, window installer
Does a casement window meet fire escape rules?
This one catches people out, because a window can be perfectly legal as a window and still fail as an escape route. Where a window is relied on for emergency escape, typically an upstairs bedroom or a loft conversion, Approved Document B requires the opening to satisfy all three of the following at once.
- An unobstructed openable area of at least 0.33 m².
- A minimum height of 450 mm and a minimum width of 450 mm. The route through the window may be at an angle rather than straight through.
- The bottom of the openable area no more than 1,100 mm above the floor.
The trap is the word "unobstructed". A standard friction stay only lets the sash swing so far, and the arm itself sits in the opening, so the clear area you can climb through is smaller than the sash. Plenty of ordinary side-hung casements measure under 0.33 m² clear once the hinge is accounted for. The fix is an egress hinge, also sold as a fire escape hinge, which swings the sash much wider and moves the arm clear of the opening. It costs more than a standard friction stay.
Ask your installer to confirm in writing which openings get egress hardware, and to give you the clear opening calculation rather than just the frame size. If the windows you are replacing already served as escape windows, the new ones must not be worse. A FENSA-registered installer should raise this before you order.
Do casement windows need trickle vents?
For most replacement jobs in England, yes. Since the 15 June 2022 update to Approved Document F, the majority of replacement windows must be fitted with trickle vents, and the governing test is that ventilation after the work must be at least as good as before. A new casement seals far more tightly than the draughty window it replaces, so ventilation that used to happen by leakage has to be provided deliberately. Our trickle vents guide sets out the room-by-room equivalent areas and the narrow exceptions.
Homeowners often ask to have them left out, on the grounds that they make the house cold. Resist that instinct. A sealed casement with no background ventilation is the recipe for streaming glass and black mould in the reveals within a single winter, which is why vents sit at the heart of most condensation problems in newly glazed homes. A quote that quietly omits them is a quote to question.
How energy efficient is a casement window?
Very, and the reason is mechanical rather than clever. Turning the handle draws the sash hard onto a compression gasket around its whole perimeter. A sliding window cannot do that, because sliding surfaces have to slide. That compression is why casements are the easiest style to make genuinely airtight, and why they perform as well as they do for the money.
For a replacement window in England, the standard to meet is a U-value of 1.4 W/m²K or lower, or a Window Energy Rating of band B or better, as set out in Approved Document L. A modern A-rated uPVC casement clears that comfortably, so treat it as a floor rather than a target.
On the saving, be realistic. The Energy Saving Trust puts the annual bill saving from installing A-rated double glazing throughout an entirely single-glazed semi-detached home at £85 a year in Great Britain and £140 a year in Northern Ireland. That is real, and it comes with a genuine comfort improvement, but it will not pay for a full set of windows on its own. Our guide to whether double glazing is worth it works the arithmetic through properly.
When is a casement the wrong choice?
It depends On a Victorian or Georgian frontage, a casement can look out of place where the street expects vertical sliding sashes, and in a conservation area you may not be allowed to swap a sash for a casement at all. In those cases, read our sash windows guide and check the rules before you buy. On flats and high upper floors where you want to clean the glass from inside, a tilt and turn window may serve you better than a standard casement.
The cleaning point is worth spelling out, because it is the complaint that arrives two years after the job. An outward-opening casement above the ground floor cannot be cleaned from inside: the outer face needs a ladder or a window cleaner, every time. A tilt and turn opens inward, so both faces are reachable from the room. On a second-floor flat that matters more than the price gap.
The one job I will not do is fit chunky casements into a row of Victorian terraces with original sashes. It cheapens the whole street, and half the time the conservation officer makes them rip it out anyway. Match the house.
Tom Bradley, window installer
The verdict on casement windows
For most homes, the casement is the best-value, best-sealing, lowest-fuss window you can buy, and uPVC is the sensible default. Save the premium for sash or timber only when the house genuinely calls for it. When you are ready to price the job, the uPVC window calculator turns your window count into a 2026 range in seconds, and if you are weighing styles, our style suggester can point you to the right one, while our sash windows guide covers the period alternative.
Frequently asked questions
A fitted uPVC casement window costs £400 to £1,000 in 2026, with around £650 typical. Aluminium casements run £540 to £1,350 and timber £760 to £1,900, reflecting the dearer frame materials.
A casement window is hinged at the side or top and opens outward, usually on a handle. It is the most common window style in UK homes, prized for a tight seal and a simple, affordable mechanism.
Yes. Because the sash presses against the frame seal when closed, a modern casement seals tightly and performs well thermally. An A-rated uPVC casement comfortably meets the Part L requirement of a U-value of 1.4 W/m²K or lower.
Casements suit the great majority of modern and post-war UK homes, including semis, terraces, bungalows and new builds. They are less appropriate for Victorian or Georgian period frontages, where sash windows are the traditional style.
Yes. A uPVC casement at £400 to £1,000 is cheaper than a uPVC sash at £600 to £1,500, because the casement mechanism is simpler. For most homes the casement is the better-value choice.
In uPVC or aluminium, almost none beyond an occasional wipe and a drop of oil on the hinges. Timber casements need repainting every 8 to 10 years to protect the frame.
The usual causes are a worn or bent friction stay hinge letting the sash drop, a lock keep that has drifted out of alignment, a compression seal that has hardened with age, or dirt in the hinge track. Cleaning and adjusting fixes many cases. If the hinge arm is bent, rusted or has stripped its fixing screws, it needs replacing.
Checkatrade puts replacement friction stay hinges at £18 to £37 per pair for parts and £25 to £40 an hour for labour, with a single window typically around £60 all in and five windows in one visit around £250. Fire escape and tilt-and-turn hinges cost more.
Under Approved Document B, a window used for emergency escape must have an unobstructed openable area of at least 0.33 m², be at least 450 mm high and 450 mm wide, and have the bottom of the openable area no more than 1,100 mm above the floor. A side-hung casement on standard hinges often falls short of the 0.33 m² clear area, which is why egress hinges are fitted where escape provision is required.
Usually yes. Since the 15 June 2022 update to Approved Document F, most replacement windows in England must include trickle vents, and the ventilation after the work must be at least as good as it was before. A reputable installer will price them in without being asked.
Yes, in most cases. If the sealed unit has misted but the frame, hinges and locks are sound, a glazier can fit a new unit at far less than the cost of a whole window. Full replacement only makes sense once the frame itself has deteriorated.
On a period property, a barn conversion or in a conservation area, usually yes: the flat profile looks right where a stormproof casement looks wrong. On a post-war semi or a new build it buys nothing you will notice, and it costs roughly 30% more for identical thermal performance.