Fenster Glazing
Aluminium Flush Windows
Aluminium flush windows give modern performance a cleaner, flatter external finish. We help you compare sightlines, colour, opening style, glazing and hardware so the final specification suits the property rather than simply reusing a standard aluminium-window package.
Key specifications
Sheerline Prestige, in four figures.
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U-value
1.0 W/m²K*
* Lowest achievable.
- Colour choice Any RAL colour
- Energy rating Up to A+
- System Sheerline Prestige
What flush means
The sash closes into the frame, not onto it.
On a standard casement the opening sash sits on the face of the frame and stands proud of it, so every opener has a step around it and a shadow line that follows the sun round. On a flush window the sash closes down into the frame and the outside of the window is one plane. That is the only difference between the two, and it is the one you see from the garden.
Drag it. One window, rendered twice, and the only thing changing is the outer frame. Sheerline put it best: a flush frame brings the perimeter of the frame and the opening sash in line with each other.
Where it belongs
The aluminium window that suits an old house.
Aluminium has a reputation for looking modern, and a standard casement earns it: the proud sash is a hard, obviously manufactured line that a stone elevation was never designed to carry. A flush window does not have that line. A flat sash face is what timber casements always had, which is why this one sits on a limestone gable under timber lintels and does not argue with it.
That is worth saying plainly because most people arrive here assuming aluminium is for extensions and glass boxes. It is very good at those. It is also the material to reach for when the frames want to be quiet and thin and a particular colour, and the building they are going into is two hundred years older than they are.
- A flat outside face, the way a timber casement sits
- Slim frames, so a small stone opening keeps its glass
- Colour chosen against the stone rather than out of a box
Choosing the material
When aluminium is the right answer.
Flush is a shape, and you can have it in uPVC for less. Aluminium is the answer when the frames need to be thinner than uPVC can go, when you want a colour it does not come in, or when the window needs to go on looking like this rather than merely working.
- Frames you barely notice
- Aluminium carries a big pane in a narrow frame in a way uPVC cannot, which is why an opening stays mostly glass. Prestige is one system with three outer frames and the flush one is the larger of them; across the range Sheerline publish sightlines from 46mm on a fixed pane to 112mm on a casement.
- Any colour, inside and out
- Twelve standard powder-coated finishes, any RAL colour to order, and a different colour inside from outside if the room wants one thing and the elevation another.
- Warm for a metal window
- Thermlock multi-chamber thermal breaks separate the outside of the frame from the inside. 1.4 W/m2K double glazed, 1.0 triple, and up to an A+ window energy rating.
- Screwed corners, not crimped
- Sheerline bind the mitres with threaded screws rather than crimping them. It is a patented detail and it matters most on a flush window, because the corner is on show rather than hidden behind a proud sash.
Figures are Sheerline's published specification for the Prestige system, which covers both flush and standard windows. What we fit, and what it costs, depends on the opening.
Our work
The house on the stone.
Dove grey Prestige frames on a Cotswold limestone cottage, photographed on a clear November afternoon. Click either image for a closer look. Dove grey frames on Cotswold limestone. Tap either image for a closer look.
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.
Colour
Twelve standard colours, powder coated in the UK.
Powder coating is baked onto the aluminium rather than painted over it, so it does not flake and it never needs redoing. Anthracite Grey and Jet Black are the two we fit most often, and both sit well against brick and render alike.
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Pure White
RAL 9010 Matt
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Hipca Gloss White
RAL 9910 Gloss
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Anthracite Grey
RAL 7016 Matt
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Jet Black
RAL 9005 Matt
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Cream
RAL 9001 Matt
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Agate Grey
RAL 7038 Matt
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Squirrel Grey
RAL 7000 Matt
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Pastel Turquoise
RAL 6034 Matt
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Chocolate Brown
RAL 8017 Matt
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Silver Metallic
Metallic effect
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Mid Bronze Metallic
Metallic effect
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Black Metallic
Metallic effect
You can have a different colour inside and out, and beyond these we can match any RAL colour, confirmed against a sample before your window is ordered. If you have a shade in mind, ask and we will tell you what is possible. Compare colours across every material
Handles
Six handle finishes, lockable as standard.
The S2 Signature range, in left and right hand versions so the operation matches the way the window opens. The release button and the screw cover cap match the finish you choose.
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White
White Powder Coat
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Black
Black Powder Coat
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Chrome
Chrome Plate
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Gold
Gold Electroplate
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Satin Silver
Satin Silver Electroplate
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Monkey Tail
Traditional Monkey Tail Handle
Handing, restrictors and key-locking are settled at survey, alongside how far the sash swings and whether the handle can be reached comfortably. See the full handle specification
Product questions
FAQs about Aluminium Flush Windows
What makes aluminium flush windows different?
The flush sash sits flatter within the outer frame, giving a cleaner external line than a standard projecting casement.
Are aluminium flush windows suitable for older homes?
They can be. We will help compare proportions, colours and sightlines so the window suits the age and style of the property.
Can I choose any RAL colour?
Yes. Aluminium flush windows can be specified in a wide range of RAL colours, subject to the chosen system and finish.
Do they still offer good energy performance?
Yes. The system uses thermally broken aluminium frames and modern glazing to support strong thermal performance.
Will you survey before ordering?
Yes. We check measurements, opening styles, frame details and installation constraints before manufacture.
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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Send the basics and the team can guide you through styles, pricing, survey and installation options.
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Where we fit
Aluminium flush 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.