Flush vs Standard Casement uPVC Windows – What’s the Difference?
When choosing new uPVC windows, most homeowners start by thinking about colour or glazing. But one of the biggest design differences is actually much simpler – how the window sits within the frame.
It might sound like a small detail, but it has a big impact on the overall appearance of your home. This is what separates standard casement windows from flush casement windows.
At Alexander Windows, our uPVC windows are made using two high-performance systems: Kömmerling and The Residence Collection. The profile is the engineered frame that determines the structure, appearance and performance of the window.
Within our uPVC range, you can choose from:
All three offer excellent insulation, security and durability. The main difference lies in the style and the character they bring to your home.
Kömmerling Standard Casement – A Classic Choice
Standard casement windows are the most familiar style of uPVC window in the UK.
The opening part of the window slightly overlaps the outer frame when it closes, creating the framed look many homeowners recognise.
Kömmerling’s standard casement windows offer:
- Sculptured or chamfered frame options
- Strong thermal efficiency
- Modern multi-point locking for security
- Durable, low-maintenance uPVC
They’re practical, reliable and suit almost any type of property, from traditional terraces to modern homes.
Standard casement windows are also typically the most cost-effective option within our uPVC range, while still offering excellent performance.
Kömmerling Flush – A Neater, More Refined Look
Flush casement windows are designed so the opening sash sits perfectly level within the outer frame. There’s no overlap, which creates a flatter and more streamlined appearance.
Kömmerling Flush offers:
- A true flush finish on the outside
- Balanced, symmetrical sightlines
- The same high standards of security and insulation
This style tends to sit slightly higher in price than standard casement, reflecting its more refined appearance. Many homeowners choose flush windows when they want something a little more design-led while still keeping a traditional feel.
The Residence Collection – Premium Timber-Style uPVC
The Residence Collection is a premium flush window system designed to replicate the character and detail of traditional timber windows.
It includes three distinct profiles:
- Residence 7 (R7) – flush inside and out for a clean, balanced look
- Residence 9 (R9) – timber-style design with a flush exterior and decorative interior
- Residence² (R2) – a more contemporary flush design inside
These windows sit at the premium end of the uPVC range and are often chosen for period homes or properties where character and authenticity matter.
Read our full guide comparing R7, R9 and R2 here.
Choosing the Right Style
All three options deliver modern performance and energy efficiency. The main difference is the style you prefer:
- Kömmerling Standard Casement – classic and cost-effective
- Kömmerling Flush – refined with cleaner lines
- The Residence Collection – premium and timber-inspired
It’s a small design detail, but how the sash sits within the frame can completely change the look of your windows. If you’re considering new windows, we’d always recommend seeing the differences in person. With our comprehensive display in our Stockport showroom, it’s easy to compare the styles and find the right fit for your home.
Looking for something even slimmer and more contemporary? We also offer aluminium window systems, which provide ultra-slim sightlines and a distinctly modern finish.