Fenster Glazing
uPVC Flush Sash Windows
Flush casement windows bring a traditional timber-inspired look to modern uPVC performance. We help you compare the frame detail, colour, handles and glazing so the windows suit older properties, newer homes and carefully updated facades.
Key specifications
uPVC Flush Sash Windows
- U-value 1.2 W/m²K
- Colour choice 16 options
- Energy rating A+ rated
- Sound reduction 35 dB
Where it fits
The window a period frontage asks for.
A flat sash face is how timber windows were made, so on a cottage, a stone frontage or a Victorian terrace a flush casement reads as joinery from the pavement where a standard casement reads as replacement. That is the whole reason the style exists, and it is why conservation officers tend to be easier about it.
Georgian bars, astragal bars and the heritage colours all belong to that argument. Cream and Chartwell Green do more for a period elevation than white does, and they cost the same to fit.
- Reads as painted joinery rather than replacement uPVC
- Cream, Chartwell Green, Irish Oak and the woodgrain foils
- Georgian or astragal bars where the frontage had them
And the other half
It is not only a period window.
Half the flush casements we fit go onto elevations with nothing period about them. A flat sash in anthracite or black brown against white render gives a crisp, modern line that a stepped sash cannot, because there is no shadow running around every opener to break it up.
It is the same argument as the cottage, arriving from the other direction: the flat face is quieter, and quiet suits a plain elevation as much as it suits an old one.
- Anthracite, black brown and the greys, inside and out
- The inside face specified separately from the outside
- One flat plane, with no shadow line around the openers
Performance
It looks traditional. It does not behave traditionally.
The look is why people choose it. Behind the look is the same six-chamber frame we fit on every other Liniar window.
- The room holds its heat
- Six sealed chambers run through the frame instead of the usual four, and each one interrupts the route warmth takes out of the room. It is the same EnergyPlus platform we fit on the standard casement.
- No draught at the corners
- The weather seal is formed with the frame rather than pushed into a groove afterwards, so it runs unbroken around every corner. Corners are where a pushed-in seal lets go first, usually a few winters in.
- A+ rated, and 1.2 W/m²K
- Whole window, on the 28mm double glazed unit this system takes. Size, layout and glass all move the real figure, so the number we agree follows your actual windows rather than a brochure.
- Quieter rooms on a busy road
- Liniar publish 35 decibels of sound reduction for this frame. If noise is the reason you are replacing the windows, say so at survey: the glass does most of that work and it is specified differently.
Security
Locked along the sash, not just at the handle.
A flatter sash is not a softer window. It locks the same way every casement we fit does, and the glass decides most of the rest.
- Held shut along the whole sash
- One turn of the handle throws locking points down the full edge of the sash, so the window is held into its seals along its length rather than at the handle alone. That is standard on every one we fit, not an upgrade.
- Glass that holds together
- A laminated pane has a bonded interlayer, so it stays in one piece instead of breaking through. It is the first thing we would suggest on a ground floor window, or any window out of sight from the road.
- Tested, and certified if you need it
- Available to PAS 24 and Secured by Design, which is what building control asks for on a new dwelling and some extensions. Tell us early if your build is covered and we will specify to it from the start.
Two faces
Flush or standard.
The same 70mm Liniar uPVC and the same fitters. The sash is the difference, and it changes both the look and the glass the frame will take.
Drag it, and watch the step disappear.
Two windows from the same studio set, shot in the same light against the same white. On the standard casement the sash stands proud of the outer frame and throws a shadow line around every opener. On the flush, it closes into the frame and the face is one plane.
| Specification | Flush | Standard |
|---|---|---|
| The sash | Closes level with the frame | Stands proud of the frame |
| Fixed panes | Matched dummy sash, so every pane reads the same | Glazed into the frame, so more glass |
| Glazing | 28mm double | 28mm double, or 36mm triple |
| Whole window U-value | 1.2 W/m²K | 1.2 W/m²K, or 0.95 with triple |
| Energy rating | A+ | A+ |
| Suits | Period frontages, and modern elevations wanting a flatter line | Most homes, and the wider specification |
Our work
Flush casements, fitted by us.
Every photograph here is a Fenster installation. Judge them on the sash line, which is the only thing separating this window from a standard one. Click any image for a closer look. Every photograph is a Fenster installation. Tap any 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
Sixteen colours outside, matched or white inside.
A uPVC colour is a foil bonded to the profile at the factory rather than paint applied afterwards, which is why the woodgrains have a grain you can feel and why none of them need repainting.
- Smooth White No foil, RAL 9003
-
White
Foil, RAL 9010
-
Cream
Foil, RAL 9001
-
Chartwell Green
Foil
-
Irish Oak
Foil
-
Golden Oak
Foil, RAL 8001
-
Rosewood
Foil
-
Anthracite Grey
Foil, RAL 7016
-
Black Brown
Foil, RAL 8022
-
Agate Grey
Foil, RAL 7038
-
Silver Grey
Foil, RAL 7001
-
Basalt Grey
Foil, RAL 7012
-
Slate Grey
Foil, RAL 7015
-
Gale Grey Finesse (Anthracite Smooth)
Foil, RAL 7016
-
Blue
Foil, RAL 5011
-
Dark Green
Foil, RAL 6009
-
Dark Red
Foil, RAL 3011
Availability, lead time and cost vary by colour, so we confirm all three before you order rather than after. 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.
-
White
White Powder Coat
-
Black
Black Powder Coat
-
Chrome
Chrome Plate
-
Gold
Gold Electroplate
-
Satin Silver
Satin Silver Electroplate
-
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 uPVC Flush Sash Windows
What is a flush casement window?
It is a casement window where the opening sash sits neatly within the frame, creating a flatter, more timber-like external appearance.
Are flush casement windows good for period homes?
Often, yes. Their timber-style proportions, foiled finishes and optional heritage details can suit older homes while reducing maintenance.
Do flush casement windows need repainting?
No. uPVC flush casements are low maintenance and only need normal cleaning and occasional hardware care.
Can they be used in bays or larger layouts?
Yes. Flush casement styles can often be used in bay and bow arrangements, subject to survey and structural suitability.
Can I choose handles and colours?
Yes. We can help coordinate frame colour, handle finish, obscured glass and any heritage-style detailing.
Can I have triple glazing in a flush casement?
Not on this system. The uPVC flush sash takes a 28mm double glazed unit only, which is what it reaches 1.2 W/m²K and an A+ rating on. If triple glazing matters more to you than the flat sash line, the standard casement takes a 36mm triple unit and reaches 0.95 W/m²K. We would rather tell you that before a survey than after one.
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.
Read on Google
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!
Read on Google
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.
Read on Google
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.
Read on Google
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 GoogleFrom our case studies
Real installs, photographed on the day.
Flush casement windows and a composite door, Little Horwood
Agate grey flush casement windows and a matching composite front door across the front of a rendered village cottage in Little Horwood.
Read case study
Flush windows and slide and fold doors, Leighton Buzzard
A full package for a Leighton Buzzard home: flush casement windows and an aluminium slide and fold door that opens the room right out.
Read case study
Flush casements, tilt and turn windows and doors, Hanslope
Anthracite grey Liniar windows and two doors across a stone barn conversion in Hanslope, with flush casements on the elevations and a tilt and turn that opens two ways.
Read case studyStart your project
Tell us about your project.
Send the basics and the team can guide you through styles, pricing, survey and installation options.
Keep exploring
Related products and service areas
Double Glazed Windows Milton Keynes
uPVC Casement Windows
Sliding Sash Windows
uPVC Tilt & Turn Windows
Bow and Bay Windows
Aluminium Casement Windows
Aluminium Flush Windows
Aluminium Heritage Windows
From the blog
Worth reading before you decide.
Trickle vents explained: why new windows have them
Since 2022, most replacement windows in England need trickle vents. What they do, why the rule exists, whether you can refuse them and how to use them properly.
How window replacement actually works, from survey to fitting
What actually happens when you replace windows: quote, technical survey, manufacture and fitting day, and what each stage decides. No mystery, no hard sell.
Draughty windows: repair or replace? An honest checklist
Not every draughty window needs replacing. A straightforward checklist of what can be fixed, seals, hinges and locks, and the signs the window is done.
Where we fit
uPVC flush sash 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.