Fenster Glazing
French Casement Windows
A French casement is a pair of side-hung sashes that meet each other instead of meeting a fixed post. The centre stile is carried on the closing sash, so it swings away with it and the whole width opens as one, exactly the way a pair of French doors does. It is a configuration rather than a window of its own: you specify it on the window you were already choosing, in uPVC or in aluminium.
Window configuration
The centre stile is carried on the closing sash.
A standard pair of windows has a mullion fixed to the frame between them, and it stays there whether the sashes are open or shut. On a French casement the two sashes are side-hung and close against each other, with the meeting stile carried on the closing leaf. Open both and the aperture is the full width of the frame.
The arrangement changes how the opening works rather than what the window is made of, so it is specified on the window you were already choosing.
Where you can have it
Five windows can be built this way.
The profile, colour, glass and hardware stay whatever that window already offers.
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uPVC
uPVC Casement Windows
The standard 70mm Liniar EnergyPlus casement, in a French pair.
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uPVC
uPVC Flush Sash Windows
Flush sash faces, so the pair sits level with the frame all round.
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Aluminium
Aluminium Casement Windows
Sheerline Prestige, for the slimmest sightlines across the pair.
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Aluminium
Aluminium Flush Windows
The flush Prestige outer frame, in a French pair.
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Aluminium
Aluminium Heritage Windows
Slim heritage sections where the elevation is period.
Means of escape
The clear opening is the full width of the frame.
Where a habitable room needs a means of escape window, what decides it is the clear opening once the window is open. A fixed central mullion costs you twice: it takes width out of the middle, and it splits what is left into two apertures rather than one. A French pair opens the whole way across.
Those are the criteria in the guidance, not a promise about a particular window: whether a unit meets them depends on the size it is made at. We work the clear opening out against the room at the technical survey, along with restrictors, handle height and safety glass, and confirm it before anything is ordered.
What Approved Document B asks for
- Clear openable area
- At least 0.33 m²
- Clear height and width
- At least 450mm each
- Height above floor
- Bottom of the opening 800mm to 1100mm
Specification
How the pair is held shut.
- Meeting stile
- Carried on the closing sash, so it swings away with the leaf rather than staying in the opening
- Locking
- The closing sash shoots bolts into the head and the cill, so both leaves are held into the frame rather than into each other
- Keeps
- Set where the two sashes meet, into the frame around the pair
- Order of opening
- One leaf is the master and carries the handle, chosen at survey
- Glazing
- The same options as the window it is built in, including obscured glass and Georgian or astragal bars across the pair
The colour range is the range of the window you choose rather than anything the configuration decides, so a French pair is available in the full uPVC foil range or in any RAL colour on aluminium.
Specification choices
Finish the design with your colours, glass and hardware.
Choose your colours, privacy glass and hardware; each guide helps narrow the detail before survey.
Product questions
FAQs about French Casement Windows
What is a French casement window?
A pair of side-hung sashes that meet each other rather than a fixed central post. The centre stile is carried on the closing sash, so when both are open the whole width of the frame is clear. It is the same arrangement as a pair of French doors, in a window.
Which of your windows can be made as a French casement?
uPVC casement and uPVC flush casement, and all three aluminium windows: casement, flush and heritage. It is a configuration you add to the window you were already choosing, so the profile, colour and hardware stay the same.
Are French casements only available in uPVC?
No. They are specified in the 70mm Liniar EnergyPlus uPVC profile or in Sheerline Prestige aluminium, including the flush and heritage aluminium sashes. The configuration does not change the system it is built in.
Is it secure without a fixed central mullion?
The locking does not rely on the post. The closing sash shoots bolts into the head and the cill of the frame, and keeps are set where the two sashes meet, so both leaves are held into the frame itself.
Can a French casement be used as an escape window?
It is the configuration most often specified for one. Approved Document B asks for a clear openable area of at least 0.33 square metres, at least 450mm clear in both height and width, and the bottom of the opening between 800mm and 1100mm above the floor. A French pair opens across the full width of the frame with no mullion in the middle, so the clear opening is the frame. Whether a particular window meets the figures depends on the size it is made at, which we work out at the survey.
Will you advise on restrictors?
Yes. We look at room use, height above ground, ventilation and any escape opening requirement when we specify the openings, restrictors and glass, and confirm it at the technical survey.
Order process
A clear process from first quote to aftercare.
Four steps. The first one has two ways in: price it yourself online, or have us come out. After that it runs the same either way.
Your price
Price it yourself on the online tool, or book a free consultation and we build the same quote with you. Both run on the same price list, so the figure matches.
Technical survey
Once you go ahead we survey before anything is made. Not a second sales visit: the measurements, thresholds and fixings the factory needs to build it right.
Installation
Fitted by our own installers rather than subcontractors, trained on the systems we sell and working carefully in a house someone lives in. We clear up after ourselves before we leave.
Aftercare
A ten year insurance-backed guarantee through the CPA on new windows and doors, and your FENSA certificate sent direct. Anything afterwards, you ring us, not a call centre.
What Milton Keynes homeowners say
Real reviews from real installations. Every one is public, so you can go and check them yourself.
Stuart Matthew
7 months ago
Fenster have just completed a front door installation on my new property - fantastic job and strongly recommend! The online design tool is great, Perry back at HQ is brilliant as is his communication. Andy, who installed the door, is a top gent and professional. Will definitely be a returning customer.
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Joanna Hayes
3 months ago
Really happy with the service we received from Fensters Windows. Aaron and Shane turned up on time and were both really friendly. They explained any issues as they went along and talked us through the different options, which we really appreciated. They did a great job fitting our new back doors and cleaned up everything afterwards. We also paid exactly what we had originally been quoted, with no unexpected extra costs. Really pleased with our new doors and would definitely recommend Fensters Windows. Thank you Aaron and Shane!
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Digger
3 months ago
We have used Fensters for years on a variety of glazing work, and 2 door installations. They are competitively priced and responsive. They take great care over measuring and specifying the work, giving you a clear quote so you understand what you are getting (thanks Perry!). The fitters are all extremely competent and personable. We had to replace our front door for accessibility reasons, they gave us confidence that our requirements would be met, reproduced the intricate leaded and stained-glass pattern of our old door, and did a quality fitting job (thanks to Johnnie and Shane!). In summary they are our go-to suppliers for all replacement and repair work.
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Silvia Peraro
2 months ago
I had an excellent experience with Fenster Glazing from start to finish. Nick Perry and David managed the initial quote to installation process seamlessly, keeping communication clear, honest, and completely stress-free. When it came to the actual fitting, Zac and Shane did a fantastic job with the installation, working efficiently and leaving everything spotless. The professionalism from the entire team was top-notch, and the final result looks brilliant. I highly recommend them.
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Bernie Raffe
4 months ago
Great service from Fenster Glazing, very happy with our new bi-fold door, glass door and windows (with built-in blinds) There was an issue with the wrong spec of glass provided to them from their supplier, so they had to temporarily board up a door and a window, but this was put right within a few weeks. Recommended, thanks.
Read on Google Zak Jessup 12 Jun 2025Cannot recommend higher! Nick and Perry were really helpful in getting my windows sorted ASAP.
Read on Google Norman Cummings 10 Jun 2025The best service ever, great workmen, very high standard and in the finish, excellent eye to detail.
Read on GoogleOur work
Recent work across the range.
Jobs we have finished recently, fitted by our own installers and photographed the day we finished. They cover the range rather than this product.
uPVC casement window, Loughton
A badly fitted window left by a cowboy builder, replaced with a two-tone Liniar uPVC casement and finished cleanly inside and out.
Read case study
Composite front door and sidelight, Milton Keynes
An anthracite grey composite front door and a full height sidelight, replacing a white uPVC door and a side panel boarded across its bottom half.
Read case study
Secondary glazing, Winslow
Six secondary glazing units in a listed Winslow home, five horizontal sliders and one lift-out, fitted inside the original windows in white aluminium.
Read case studyStart your project
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Where we fit
French casement windows in Milton Keynes and the towns around it.
Each town has its own page: the homes there, what to check before you order, and who to ask about permission.