Flush And Non-Flush Casement Windows – What’s The Difference?

Flush And Non-Flush Casement Windows – What’s The Difference?

The casement window is one of the most famous and celebrated window styles sold in the UK and there are two versions of it available at TWC – flush casement windows and non-flush casement windows.

A flush casement design is one that is completely flat due its window sashes sitting flush against the window frame, whereas a non-flush casement window has sashes that ever so slightly overlap the window frame.

If you come to our Swindon showroom, get a side-on view of both products and you will understand what we mean.

Interested in finding out more? We have some extra info to share about flush and non-flush casements.

The history of flush and non-flush casement windows

Flush casement windows first came to prominence in the 19th century and were developed using timber as wood was the prime window material at the time.

Still to this day, lots of Victorian, Edwardian and late Georgian properties in Wiltshire, Oxfordshire and nationally with their original windows have timber-framed flush casements.

The non-flush casement window predates the flush design, created in the 18th century. It was built from iron and done so by blacksmiths, before wood usurped it, and latterly UPVC and aluminium.

A set of casement windows

The flush window is enjoying a renaissance

A renewed demand for flush windows in recent years has led to window installers like us integrating them into our product line. Part of the reason for their rebirth is people’s longing for windows with a contrasting aesthetic to other available designs.

‘Envisage’ is the name given to our flush window collection and the template for its design was the original flush timber casement window – we’ve copied its traditional proportions and lines, but manufactured Envisage using a UPVC profile to ensure it obeys modern thermal performance and secure requirements, and is easy to maintain.

A close-up of a flush casement window frame

Flush or non-flush – which do I buy?

Definitely a flush casement window if your property happens to be in a conservation area because you’re more likely to be granted permission to install flush windows by planning committees as they acknowledge how good they are at sustaining the look of historical residences.

A flush sash window also has the straight lines and symmetry to complement modern residences – for these sorts of installations, Black and Anthracite Grey are the top two colour choices.

There are no parameters where the casement window is concerned as it can work with just about any type or age of property.

An oak effect flush casement window

A TWC advisor can tell you more about flush and non-flush casement windows over the phone, in-person or at your home, whatever suits you most.


Our made-to-measure windows and doors have the potential to change your home not just on the outside, but the inside too. From the very latest energy saving windows in maintenance free UPVC to a host of replacement doors – all guaranteed to fit perfectly with your home.


Make your home warmer, quieter and more secure by fitting our very latest energy efficient replacement windows.



Our range of replacement doors offer all the advantages of low maintenance and high levels of security for total peace of mind.



Simply fill in your details for your free, no obligation quotation, and click "Get Quote"


Everyone is welcome to come in and browse around our Swindon or Oxford showroom, where our friendly sales team will be pleased to help with any questions you may have.


Want to speak with an Advisor? Give us a call on 01793 781413

Our friendly team will be pleased to help with any questions you may have.

Back To Our Blog