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The GS25 Frameless Sliding Door: Engineered for Scale

The GS25 is our flagship bonded sliding door. Designed for new build projects where the brief demands maximum glass, minimum frame and no compromise on performance, it is the door you specify when nothing else will do.

With a 25mm interlock sightline, panels up to 3.5m wide and 3.5m high, a maximum panel weight of 500kg and the option to conceal the entire perimeter frame within the building structure, the GS25 delivers what very few sliding doors can. That is, a near-invisible connection between inside and outside at genuine architectural scale and design.

What Makes the GS25 Different

Every sliding door manufacturer talks about slim sightlines. The GS25 goes further. When the outer frame and track are hidden in the structure, all you see is glass. The 25mm interlock between panels is the only visible aluminium, and at that width it recedes rather than dominates. The result is a sliding door that looks less like a door and more like a moving glass wall.

This is a bonded glass system. The glass is structurally adhered to the aluminium frame, which is what allows the sightlines to be this slim while maintaining the structural integrity needed for panels of this size and weight. It is the same construction principle used across our GS15 and GS20 systems, but the GS25 is engineered for the largest and most demanding openings.

The GS25 is designed exclusively for new build applications. The hidden frame detail requires the structural opening to be built around the door system. This is not a replacement for an existing patio door. It is a product for projects where the glazing is designed into the architecture from the start.

What We Have Improved

The original GS25 has always been a strong product. What we have done is make it better in the areas that matter most to installers and homeowners.

The track system has been re-engineered. Where the standard product uses a multi-wheel arrangement, we have developed a cleaner, more refined track design that improves the smoothness of operation and reduces the mechanical complexity at ground level. The result is a door that glides with less resistance and a track that is simpler to install and maintain.

The handle has also been redesigned. The new interlock handle is more refined in both appearance and operation, sitting neatly within the 25mm profile and delivering a precise, controlled locking action. Flush security hardware is also available for projects where a completely clean face is required.

These are not cosmetic changes. They reflect our approach to continuous product development and identifying where the real-world experience of making, fitting and using the door can be improved, and engineering the solution.

Large Glass Requires Serious Engineering

Creating minimal sightlines is only half the challenge. The real engineering challenge comes from supporting large areas of glass safely and reliably over many years of daily use.

The GS25 supports:

At these sizes, factors such as wind loading, structural movement, glass weight and long-term alignment become critical.

A sliding door installed on a sheltered suburban development faces very different conditions to one installed on a clifftop property, coastal location or exposed countryside site.

This is why slimline sliding doors should never be assessed on sightlines alone. Structural performance, testing, hardware specification and manufacturing quality are equally important.

At Glideline, our philosophy has always been to balance aesthetics with engineering, ensuring the door remains reliable long after installation.

Scale and Capability

The GS25 is built for large openings. The numbers tell the story:

Corner configurations are available with either a movable corner post or a frameless bonded corner — the latter removing the vertical post entirely and creating an uninterrupted glass corner that opens completely. U-shape configurations extend this further, wrapping glass around two corners for the most dramatic openings.

These are not theoretical maximums. They are the parameters within which the GS25 is tested and manufactured. If your project calls for a 3.5m x 3.5m sliding panel, or a six-pane configuration, or a frameless glass corner, this is the system that does it.

Performance

The GS25 is independently tested across all key performance metrics:

Thermal Performance U-value from 0.88 W/m²K with triple glazing, comfortably exceeding current Building Regulations and well positioned for the Future Homes Standard. With 46mm triple glazing, the thermal performance is strong for a door with this much glass area.

Acoustic Insulation Rw up to 43 dB. For homes near roads, railways or other noise sources, this is a meaningful figure that makes a noticeable difference to the internal environment.

Air Permeability Class 4 (EN 12207). The highest possible classification.

Water Tightness Class E900 (EN 12208). This is an outstanding result, indicating the door withstood 900 Pa of water pressure. For context, this is at the very top of the scale and confirms the GS25's suitability for exposed and coastal locations.

Wind Resistance Class C5 (EN 12210). The highest classification for both wind pressure (2,000 Pa) and deflection. The door handles the maximum test pressure with minimal frame movement.

These figures are verified on the actual GS25 system, not theoretical projections from a profile supplier.

Glazing

The GS25 accepts glazing units up to 46mm thick, accommodating both high-performance double glazing and triple glazing. With triple glazing using a Ug of 0.5 W/m²K, the system achieves a whole-door U-value from 0.88 W/m²K.

As a bonded system, the glass is factory-fitted by Glideline. This ensures the structural bond between glass and frame is controlled, consistent and performed under the right conditions — which is essential for the long-term integrity of a bonded sliding door.

Solar control glazing is available for south-facing or fully exposed installations where heat gain needs to be managed.

Hidden Frame and Track Solutions

The GS25 is designed to disappear into the structure. The perimeter frame can be fully concealed within the wall, floor and ceiling, leaving only the 25mm interlock visible. This is what creates the near-invisible glass wall effect.

We also offer a hidden track solution. The floor track can be recessed and integrated into the floor finish, eliminating any visible rail at ground level. Combined with our bespoke drainage solution, this allows a completely flush threshold with no compromise on water management.

These details matter. A sliding door of this scale needs to feel part of the build and not just a sliding door you see at eye level. As a result, the hidden track and bespoke drainage options ensure the finished installation looks as clean from the inside as it does from the outside.

Colour and Finish

The GS25 is available in over 150 RAL powder-coat colours, with Anthracite Grey (7016M), Jet Black (9005M) and White (9016G) as standard finishes. Dual colour options are available for projects where the interior and exterior colour schemes differ.

Textured finishes, wood-effect powder coating and anodised aluminium are all available on request.

All powder-coated finishes are to the Qualicoat standard. Anodised finishes are to the Qualanod standard.

Where the GS25 Fits

The GS25 is not for every project. It is for projects where the sliding door is a defining element of the project and where homeowner and architects want maximum glass, minimal frame, large-format panels and the kind of engineering that makes it all work reliably for decades.

GS25 Frameless works particularly well in:

Contemporary new builds Where the design centres on large, open-plan living spaces with full-width glazing connecting the interior to the garden, terrace or landscape beyond.

Grand Designs-style projects

Where the ambition, scale and budget justify a sliding door system at the very top of the market.

Coastal and exposed locations

Where the Class E900 water tightness and Class C5 wind resistance provide the performance needed to handle demanding weather conditions.

Corner and U-shape configurations where the architecture wraps glass around corners to create dramatic, fully opening glazed walls.

For standard residential openings, rear extensions and projects where a beaded system or smaller panel sizes are appropriate, our Aspect sliding door, GS15 and GS20 systems offer excellent alternatives at different points in the range.

Part of the Contemporary Glideline Range

The GS25 sits at the top of our sliding door range, alongside the GS15 Minimal, GS20 Classic and the new Aspect beaded sliding door. Together with the GB49 bifold, GPD80 pivot door and GR49 residential door, Glideline offers one of the most comprehensive aluminium door ranges from any single UK manufacturer.

All products are designed, manufactured and tested at our expanding Great Yarmouth facility, supported by the GlidelineGO app for order tracking, drawing approval and project management.

For Trade Installers, Architects and Specifiers

The GS25 is not an off-the-shelf patio door, it is a specialist sliding door system designed for projects where scale, performance and appearance all matter equally.

We regularly support:

Support includes:

By involving Glideline early in the design process, potential issues can often be identified before construction begins, helping projects run more smoothly and ensuring the finished installation performs exactly as intended.

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