Compare The Best Flush Casement Window Choices for Your Home

What choices are available for my home’s best flush casement window? Let’s start with the basics.

The term casement describes a window attached to its frame by one or more hinges, typically opening outwards. Historically, these were held open by a “casement stay”—a small metal arm connecting the sash to the frame.

Flush Casement Window History

Flush casement windows defined the aesthetic of 19th-century Edwardian and Victorian homes. Originally crafted from timber, they were the standard before sliding sash windows became dominant in larger city properties.

We call them “flush” because of their external profile: the opening sash (when closed) sits completely flat within the frame. Early glass manufacturing limitations forced the use of “Georgian bars” to hold smaller panes together. Today, advances in technology allow us to recreate this look with high-performance double or triple glazing, reducing the design from 6 panes down to a clean 2-pane look if desired.

Flush vs. Stormproof: What’s the Difference?

Most windows installed since the 1950s are “Stormproof” casements. In this design, the opening sash features a “lip” that overlaps the frame to provide a weather seal. This creates a window that sits proud of the frame.

While effective, stormproof windows lack the clean lines of traditional joinery. The recent revival of flush windows is driven by homeowners who want the high thermal performance of modern windows but despise the bulky, plastic look of standard stormproof frames.

Best Materials for a Flush Casement Window

We supply and install uPVC, aluminium and timber flush casements across Andover, Hampshire and surrounding counties. Here is how they compare:

Conservation & listed buildings: quick guidance

• Listed buildings: You will likely need Listed Building Consent. Repair is often prioritised over replacement—always speak to your local officer first.
• Conservation areas: Rules vary by council. Even changing the colour (e.g., White to Agate Grey) can trigger a planning application. Check the Planning Portal early.

Thermal, security & noise—specs that matter

• Glazing: A-rated double is sufficient for most homes; 44mm triple is available on R7/R9 and aluminium sets for ultimate efficiency.
• Security: Look for multi-point locking, internally beaded glazing, and key-locking handles.
• Acoustics: If noise is an issue, ask for acoustic laminated glass—it often outperforms triple glazing for sound reduction.

Compare Your Flush Casement Window Choices

At the KJM showroom in Andover, Hampshire, we have full-sized examples of these systems. Seeing the corner joints and finish in person is the best way to decide.

1. Sheerline Flush Aluminium Window

The Sheerline system (new to KJM in 2023) offers the perfect balance of modern strength and heritage styling. It features a unique “stepped” outer frame that looks incredible in black or grey.

2. Deceuninck Flush Casement uPVC Window

Deceuninck offers over 30 colourways from stock. Their “Graf weld” technology ensures the corner joints are seamless, making it one of the smoothest uPVC finishes on the market.

3. Residence 7 and Residence 9

Residence 9 was designed specifically to replicate 19th-century timber designs for conservation areas. It has a 100mm frame depth (just like old timber). Residence 7 is the slimmer, more modern flush version (75mm depth).

4. Timber Windows

For purists, nothing beats natural wood. Our partner, George Barnsdale, manufactures engineered timber flush casements that resist warping and twisting, finished in microporous paint that lasts for years.

Explore the Ranges

Ready to see the options? Click below to view full specifications.

• uPVC Flush Casement Windows
• Residence 7 Windows
• Residence 9 Windows
• Sheerline Aluminium Flush
• Timber Flush Casement

Flush Casement Windows FAQ