December 4, 2023

Who makes the thinnest sliding doors?

Written by Rebecca Clayton

Thin sightlines in sliding doors; what “thinnest” actually means

When people ask “who makes the thinnest sliding doors?”, they usually mean the visible vertical line where two sliding panels meet. You will also hear this called the interlock, meeting stile, or sightline.

If you have searched this topic already, you will have seen numbers like 15mm, 20mm and 21mm. These figures are usually referring to the centre interlock; the vertical join where two sliding panels meet. That centre number is only one part of the overall look; the visible frame at the head, jambs and threshold can vary significantly depending on whether the outer frame is expressed or concealed into surrounding finishes.

Within the IQ Glass range, our slimmest framed sliding system is minimal windows®, typically detailed with a 21mm meeting profile where panels meet; flush threshold detailing is available for a clean internal to external transition.

Like-for-like; what to check before you compare

• What is being measured; centre interlock only, or a wider locking stile

• Whether the quoted dimension is consistent around the set; or only at the centre join

• The configuration; single-direction or bi-parting, number of tracks, number of sliding sashes

• The detailing; concealed outer frame or visible frame at the head, jambs and threshold

• The practical spec; glazing build-up, U-value for the full door set, air and water tightness, locking approach, and maximum panel sizes and weights

• Request dimensioned section drawings; meeting stile, head, jamb and threshold

What is a sliding door interlock?

The interlock is the central vertical junction where one sliding panel overlaps and locks into the other. It has to provide rigidity as well as weather sealing; in many ultra-slim systems, the interlock also functions as the pull handle. Because it is the most visible part of a modern sliding door, it is the dimension most often used when people talk about “the slimmest” doors.

Slim Framed Sliding Glass Doors from minimal windows®

Slim framing helps blur the boundary between inside and outside, even when doors are closed. Minimalist systems achieve this by reducing the visible meeting profile and, where required, concealing the outer frames into surrounding finishes.

minimal windows® sliding doors are typically detailed with a 21mm vertical meeting profile where panels meet. Combined with flush track detailing, this supports floor-to-ceiling glass elevations suited to extensions, renovations and contemporary new builds with a modern, minimal design aesthetic.

For projects that want an even more integrated appearance and updated detailing, the minimal windows® Next Generation platform (NGS) introduces improvements to base design, sealing and automation options.

The minimal windows® Next Generation sliding glass door system (NGS)

NGS develops the minimal windows® platform with updated detailing designed to reduce the apparent frame at the threshold when detailed correctly, while improving day-to-day usability.

Key updates include soft-close options for smoother operation, updated gasket and sealing details intended to improve weathertightness compared with older brush seal approaches, and a stepped glass option to reduce the apparent base line for a cleaner floor-to-ceiling aesthetic.

For oversized sliding glass doors, automated options can be specified with maintenance access considerations built into the head detail. Telescopic configurations can also be used so multiple sashes move together for wider clear openings.

Slim sightlines come with design constraints

A slimmer interlock is not automatically a better door. Ultra-slim sliding systems often rely more heavily on the glass for stiffness, and there can be limits on panel size, height, exposure and location. Wind load and deflection calculations may be required to confirm the correct configuration, and some ultra-slim ranges have fewer opening modes or hardware options than thicker, more conventional sliding doors. Installation also matters more with large-format sliders; correct setting-out, thresholds and drainage details have a direct impact on performance.

Aluminium Sliding Glass Doors 

Aluminium framed sliding doors are at the forefront of contemporary architectural design. Our aluminium framed range offers slim profiles from around 30mm, creating large elevations of aluminium framed sliding glass with a clean contemporary finish.

Multiple configurations are available, supported by modern fabrication techniques to achieve smooth operation and long-term durability.

Ultra-slim aluminium sliding glass doors can be a more cost-effective route to slimmer sightlines than standard patio doors, while maintaining a modern finish and strong performance.

Slim steel framed doors

Elegant, thermally broken steel doors from IQ can be customised to suit a wide range of architectural specifications.

IQ’s slim galvanised steel doors can be finished in any RAL colour, as well as stainless steel and architectural bronze effects; this supports unique, luxury sliding door installations.

With a structural thermal break, these steel sliding doors can maintain strong thermal performance. They can also be engineered with integrated or applied bespoke glazing bars to create an industrial or heritage aesthetic.

If your project has strict requirements, including listed properties, we can develop bespoke solutions that replicate original profiles while targeting modern performance expectations.

Timber framed sliding glass doors systems

New Avino high specification timber sliding doors offer the warmth of real timber alongside modern performance detailing.

Timber sliders typically present a larger visible frame than ultra-slim aluminium systems. Many configurations feature around 5cm of visible frame around the timber leaf, with flush threshold detailing available depending on specification.

Our range of sliding door designs combines high performance glazing and weather sealing with a wide choice of finishes; this helps match contemporary or classic architecture without compromising performance.

If you are choosing primarily on the thinnest visible meeting profile, minimal windows® is our slimmest framed sliding system at 21mm where panels meet, with flush threshold detailing available for a seamless transition between the internal and external living areas. When comparing “thinnest” claims, always request dimensioned section drawings for the meeting stile, head, jamb and threshold; published figures can refer to different details.

Frequently asked questions about thin sliding door sightlines

What is a sliding door sightline?
It is the visible width of frame at key points; most “thinnest” claims refer to the centre interlock where two sliding panels meet.

Is a smaller sightline always better?

Not always. The centre sightline is only one detail; also check the tested performance of the full door set (U-value, air and water tightness), how the system seals and drains, the locking and handle design, glazing thickness, and maximum panel sizes and weights. The best choice balances sightlines with performance and practicality for your project.

What is a “ghost” sliding door?
It is a fully concealed frame approach; the head, jambs and track are hidden so the glass appears to slide from within the wall or floor.

How do I compare systems properly?
Ask for dimensioned section drawings showing the meeting stile, head, jamb and threshold; confirm what measurement is being quoted and for which configuration.

Are you looking to specify sliding glass doors on your next project? Contact our friendly team today!

01494 722 880

hello@iqglassuk.com