Flush Windows vs Casement Windows

What is the difference between Flush Windows and Casement Windows?

At a glance, flush and standard casement windows may look similar, but the real difference lies in how the sashes (the part of the window that opens) sit within the frame:

• Casement Windows: On traditional casement windows, the sash sits proud of the frame. This means the window opener overlaps the outer frame slightly, giving a more contoured or stepped appearance from the outside.
• Flush Windows: With flush designs, the sash aligns flat against the outer frame when closed. This produces a smooth, streamlined look that feels modern yet works equally well on traditional homes where a neat finish is desired.

Aesthetics

• Flush Windows: Unlike standard windows where the sash often overlaps, flush windows close in line with the frame, giving a uniform, slim profile. The result is a cleaner, more refined appearance that enhances both period-style and contemporary properties.
• Casement Windows: Casement windows are versatile and suit both traditional and modern homes. Their slightly raised sash design has been the standard for decades and still looks smart and functional in most settings.

Functionality

Both window types work in the same way. Hinged at the side or top, they open outwards and can be paired with modern features like multi-point locking systems, double or triple glazing, trickle vents, and energy-efficient profiles.

Are Flush Casement Windows More Expensive?

In general, yes, flush casement windows tend to be slightly more expensive than standard casement windows. Here’s why:

• Manufacturing: Flush designs require more precise engineering and additional detailing to ensure the sash aligns perfectly within the frame.
• Materials: High-quality flush windows often use stronger, thicker profiles to support the flush alignment, and are usually paired with premium finishes like woodgrain effects.
• Aesthetics: Because flush windows are designed to mimic timber and meet planning requirements in conservation areas, they are considered a premium product.

However, we believe premium style shouldn’t come at a premium price. That’s why we offer trade prices to everyone and back it up with our price match guarantee, so you always get the best deal, whether you’re upgrading a period property or building a new one.

Energy Efficiency: Flush vs Casement

Both flush and standard casement windows can deliver excellent energy performance when fitted with high-quality glazing and warm-edge spacer bars. However, flush windows may offer a slight edge due to their tighter seals and sleeker design, which reduces potential draught points. At Modern UPVC Windows, both window styles can come with A+/A++ ratings, ensuring year-round thermal comfort and lower energy bills.

Installation Differences

While flush and standard casement windows follow a similar installation process, flush windows require a higher level of precision. Because the sash sits level with the outer frame, installers must ensure a perfect alignment to maintain the clean, seamless look. Standard casement windows are slightly more forgiving due to their overlapping design.

All of our windows, whether flush or casement, are made to measure and supplied ready for straightforward installation, whether you’re fitting them yourself, working with a professional, or opting for our expert installation service.

Noise Reduction Performance

There’s minimal difference in noise reduction between flush and standard casement windows when fitted with the same double, triple, laminated or acoustic glazing. Since the sash construction and glazing unit are key factors, both styles can achieve strong acoustic insulation, ideal for homes near busy roads or in urban areas.

Durability and Maintenance

UPVC flush and casement windows are equally durable, weather-resistant, and low maintenance. Flush windows may have a slight advantage in terms of reduced external overhangs, which limits the areas where dirt and water can collect. Both styles are built to last decades with minimal upkeep and are backed by our 10-year guarantee.

Security

Security levels are comparable across both styles. Flush windows often feature the same multi-point locking mechanisms as standard casement models. All our windows are PAS24 accredited and internally glazed as standard, with optional laminated or toughened glass for added peace of mind.

How to Decide Between Flush and Casement Windows

Choosing between flush and casement windows comes down to your home’s style, your design preferences, and your budget. If you want a clean, minimal finish or need windows that blend seamlessly with period features, flush casement windows are a great choice. They’re especially suited for heritage homes or homeowners looking to replicate traditional timber aesthetics.

On the other hand, standard casement windows offer timeless appeal, excellent functionality, and a lower price point, making them ideal for modern builds and renovation projects alike. Whichever style you choose, you’ll enjoy long-lasting quality, great insulation, and full customisation at Modern UPVC Windows.

Get Started

Browse our full range of window styles including flush and standard casement windows and customise your ideal design using our online designer tool. Select your preferred window type, experiment with colours and glazing options, add bar designs and hardware, and get an instant price.