Deceuninck Flush Casement Windows to a Hertfordshire Garden Room

This Hertfordshire garden room, transformed with modern Deceuninck flush casement windows. Originally fitted with an earlier generation of woodgrain uPVC windows and doors that were dated. While functional at the time, the bulky hinges, mismatched colour hardware and chunky proportions no longer suited how the space was being used, or the new grey cedar-clad colour.

The homeowners wanted the room to feel lighter, more contemporary and genuinely usable throughout the year.

Deceuninck Flush Casement Windows to a Garden Room and Annexe

Picture of grey cedar clad garden room with woodgrain old windows.
Before. AFteThe original dated woodgrain uPVC windows

At LB Window Systems, we were asked to replace the existing windows and doors with a modern flush solution that would improve appearance, insulation and security, without losing the practical benefits of uPVC.

The building itself is a well-constructed and fully insulated brick and grey timber-clad insulated garden room, now used as a multi-purpose habitable space and annexe rather than simple storage or occasional space. The new glazing needed to:

  • Look refined and architectural, not like an add-on
  • Improve thermal performance for year-round use
  • Provide better security and smoother operation
  • Sit comfortably alongside the timber cladding and brickwork

Deceuninck flush casement windows in a grey finish

deceuninck flush casement windows in a grey cedar clad and brick annexe garden room
After. New Deceuninck flush casement windows

We specified Deceuninck Collection flush casement windows, part of our overall extensive windows collection, and matching French doors, finished in smooth grey externally with white internally. This combination gives the exterior a clean, contemporary look while keeping the interior bright and neutral.

Flush casement windows were chosen specifically for their timber-inspired detailing. Unlike older uPVC designs with proud opening sashes and visible welded joints, today’s flush systems sit level within the frame and use timber-look mechanical joints.

The result is a far more authentic appearance that works just as well on a garden room or annexe as it does on a main house.

Modern uPVC. A clear generational upgrade

The contrast between old and new is immediate. The original doors relied on thick, exposed hinges and non-matching handles, typical of early uPVC systems that required heavy hardware for strength. Modern uPVC has moved on significantly.

inside view of deceuninck windows
Inside view of new windows and French Doors

The new flush windows and doors benefit from:

  • Multi-chamber uPVC frames for improved thermal efficiency
  • Advanced multipoint locking systems that no longer require oversized hinges
  • Slimmer, better-proportioned profiles
  • Consistent, well-finished hardware throughout

This re-engineering means uPVC windows now look substantially better than they did in previous decades, while also outperforming them in strength, security and insulation.

Now the new windows and doors provide better security, improved energy efficiency and better internal comfort. Windows and doors are glazed with high performance glass, having a soft-coat low-emissivity coating, warm edge spacer bars and argon gas fill.  The doors have toughened glass as standard.

Replacement Latest Generation Windows for your Home or Garden Building

The garden room has been transformed into a smart, secure and comfortable extension of the home. Visually, the flush grey windows complement the timber cladding and brickwork perfectly.

Functionally, the space is now warmer, quieter and suitable for use all year round.

This project is a strong example of how modern flush casement uPVC windows  with the latest design and engineering, can be the right solution for modern garden rooms and annexes. Particularly where appearance matters as much as performance.

At LB Window Systems, we specialise in upgrading garden rooms, annexes and outbuildings with modern window and door solutions that balance design, performance and long-term reliability.

This Hertfordshire project shows just how far flush uPVC windows have evolved, and why they now deserve serious consideration in any setting.

Project details

Location: Berkhamsted, Hertfordshire
Property type: Insulated garden room / annexe
Products installed: Deceuninck Collection flush casement windows and French doors
Finish: Smooth grey external, white internal
Project type: Replacement windows and doors