Frameless Automatic Sliding Doors: Glass, Weight and Safety

Frameless automatic sliding doors are the cleanest-looking entrance a commercial building can have: full-height toughened glass, no visible stiles or rails, and an operator hidden in a slim header above. They are popular in showrooms, hotel lobbies, corporate receptions and retail fronts where the brand wants the building to be seen through the door rather than around it. Behind the clean look, frameless automatic sliding doors are a more demanding specification than framed doors, because the glass itself becomes the structure.

This guide explains how frameless automatic sliding doors are built, how the glass is held and guided, what the weight of the glass means for the operator, how security, draughts and safety differ from a framed door, and what to decide before asking for a quote. MC Automations supplies, installs, commissions and services frameless automatic sliding doors on our MC-125 sliding operator, and we service frameless entrances from other manufacturers as well.

What makes a door frameless

On a framed sliding door each leaf is a glass panel set inside an aluminium frame. The frame carries the hardware, the seals and the lock, and the glass is just the infill. Frameless automatic sliding doors remove that frame. The glass panel is clamped at the top into a rail that hangs from the operator’s carriages, and the bottom edge is kept in line by a floor guide. There are no vertical stiles, so the leading edges are bare, polished glass.

That changes almost everything about the leaf. The glass must be strong enough to be the leaf, it must be held securely at a single edge, and every fixing that a frame would normally hide has to be designed in from the start. Frameless automatic sliding doors are not simply framed doors with the frame left off.

The parts of a frameless leaf

• Toughened safety glass. The leaf is a single sheet of toughened, or toughened and laminated, safety glass. The thickness is chosen for the leaf size and the site and confirmed by the glazier.
• Top clamp rail. An aluminium profile that grips the top edge of the glass and bolts to the operator’s carriages, with adjustment for height and level.
• Floor guide. Keeps the bottom edge in line. Frameless leaves usually run in a slim guide or channel because there is no bottom rail to guide.
• Edge seals or brushes. Optional seals on the glass edges reduce draughts and dust where the leaves meet the fixed panels.
• Locking. Usually an electromechanical lock in the header that locks the carriage, sometimes with a floor lock at the bottom edge.

Glass weight decides the operator

Glass is heavy. Float glass weighs about 2.5 kg per square metre for every millimetre of thickness, and toughening does not change the weight. That makes it simple to estimate the weight of frameless automatic sliding doors before anything is ordered.

A leaf 1 100 mm wide and 2 400 mm high is 2.64 m² of glass. In 10 mm glass that is about 66 kg; in 12 mm glass about 79 kg. Add the top clamp rail and fittings and the leaf is comfortably inside what our MC-125 operator is rated for: a single sliding leaf up to 150 kg, or bi-parting leaves up to 2 × 120 kg. Much larger leaves, or laminated build-ups for security, can push the weight up quickly, which is why we work out the leaf weight first and choose the configuration second.

The clear opening the MC-125 covers runs from 1 450 to 3 100 mm on a single-slide door and from 2 500 to 5 000 mm bi-parting. Most frameless automatic sliding doors are bi-parting, with two moving leaves meeting in the middle and fixed glass panels either side, because that gives a wide opening with leaves of manageable weight. The MC-125 sliding door operator page lists the full specification, and the automatic sliding doors page covers framed and frameless layouts side by side.

Framed or frameless: the honest trade-offs

Frameless automatic sliding doors are a design decision with real consequences. They are the right choice for many entrances and the wrong one for some. Here is how they compare with a framed door on the points that usually matter.

• Appearance. Frameless wins outright. Maximum transparency, minimal metal, a cleaner line to the facade.
• Security. A framed leaf has more places to fix locks and reinforcement. Frameless automatic sliding doors rely on the header lock and, where fitted, a floor lock. For out-of-hours security many sites add a second locked door line behind the glass; our guide to automatic door security covers the options honestly.
• Draughts and dust. Framed leaves carry continuous seals. Frameless leaves rely on edge seals or brushes and on accurate gaps, so they are slightly less tight against wind and dust.
• Breakage. If a frameless leaf breaks, the whole leaf is replaced and the door is out of action until new toughened glass is made to size. Toughened glass cannot be cut after toughening, so replacement glass has to be made to size.
• Weight. Frameless leaves can be heavier for their size, which puts more emphasis on carriage set-up and roller condition.
• Cost. Toughened glass made to size, clamp rails and the fixed panels usually cost more than a standard framed leaf, though the operator itself is the same.

Safety on frameless automatic sliding doors

All automatic doors are safety equipment, and frameless automatic sliding doors bring a few points of their own.

Making the glass visible

Clear glass with no frame can be hard to see. Frameless automatic sliding doors need manifestation, the bands or markings applied to the glass at eye level so that people, including people with low vision, can see that there is a door. Branding or a frosted band often does the job and looks deliberate rather than added on.

Sensing and safety zones

Activation sensors open the door; presence sensors keep it open while someone is in the threshold and stop it closing on them. On frameless automatic sliding doors the sensors are mounted on the header, so the header design should leave room for them. Our guide to automatic door sensors explains the difference between the sensor types.

Finger traps and edges

Where a sliding leaf passes a fixed panel there is a gap that can trap fingers. The gap is set at installation and protected by the door’s force limits and sensing, and the leaf edges are polished so there are no sharp corners. Children’s hands at the leading edge are a particular concern in retail and hospitality, and the commissioning settings take that into account.

Glass standards

Safety glazing in doors is covered by SANS standards published by the South African Bureau of Standards. The glazier confirms the glass type and thickness for the leaf size and position, and your building or fire consultant confirms what applies to the particular entrance. MC Automations supplies and commissions the automation; we do not certify glazing.

Power cuts and emergency behaviour

Load shedding is a design question for every automatic entrance. Frameless automatic sliding doors behave like any other sliding door on the MC-125: with a battery backup fitted the door keeps operating through an outage, and without one it goes to the state chosen for the building. The safe state, open or closed, depends on the escape route and is decided with the building’s consultant. Our guide to automatic doors and load shedding covers the choices.

Where frameless automatic sliding doors work best

• Showrooms and retail fronts where the product should be visible from the street. See our guide to automatic doors for shops.
• Hotel and corporate lobbies where the entrance is part of the interior design. Our hotel automatic doors page covers lobby entrances.
• Internal partitions such as office suites, clinics and meeting floors, where wind and weather are not a factor.
• Glass facades where a framed door would interrupt the line of the curtain wall.

Frameless automatic sliding doors are a weaker fit for exposed entrances facing strong prevailing wind, for very high-traffic entrances where impact damage is routine, and for openings that need high security out of hours without a second line of protection. In those places a framed leaf, or frameless with a security layer behind it, is usually the better answer.

What to decide before you ask for a quote

A firm quote for frameless automatic sliding doors needs the same basics as any automatic entrance, plus a few glass decisions.

• The structural opening width and height, and what the header will fix to.
• Single-slide or bi-parting, and whether there are fixed side panels.
• The glass: toughened or toughened laminated, clear or tinted, and the manifestation design.
• Internal or external, and how exposed the entrance is to wind.
• Traffic level and opening hours, which set the duty and the service interval.
• Locking and access control, if the door is locked out of hours. Our automatic door access control page covers readers and locks.
• Power at the header, and whether battery backup is wanted.

Operator pricing for the MC-125 starts at R27 590 excl VAT. The glass, clamp rails, fixed panels, header cover and installation are quoted per opening, because frameless automatic sliding doors are made to the building. Our automatic door prices guide explains what moves the total.

How frameless automatic sliding doors are installed

The order of work matters more on frameless automatic sliding doors than on framed doors, because the glass is made to measurements taken from the finished opening. A typical sequence looks like this.

• Survey. We measure the structural opening, check what the header will fix to, check the floor level along the full travel and confirm power at the header position.
• Header and operator. The header is fixed level to the structure and the operator, carriages and clamp rails are installed and set.
• Final glass measurements. Once the header is fixed and the floor finish is down, the glass sizes are confirmed. Toughened glass ordered from drawing dimensions before the floor is finished is a common source of gaps that are too large or too small.
• Glazing. The toughened leaves and fixed panels are fitted, clamped and levelled, and the floor guide is set to the glass.
• Commissioning. Opening and closing speeds, forces, hold-open time and sensing are set and tested with the people who will use the entrance in mind.
• Handover. The site receives the operating instructions, the commissioning settings and the service plan.

Our guide to automatic door installation covers each stage in more detail.

Common mistakes with frameless automatic sliding doors

• Ordering glass too early. Measurements taken before the header and floor are finished lead to wrong gaps. Measure from the finished opening.
• Ignoring the floor. The floor guide needs a level finished floor along the whole travel. A mat well or tiles laid after installation can make a frameless leaf rub.
• Underestimating weight. Large laminated leaves get heavy fast. Work out the weight first, then choose the operator configuration.
• Leaving manifestation to the end. Markings designed in with the branding look intentional; markings added after a near-miss look like an afterthought.
• No plan for out-of-hours security. Frameless automatic sliding doors look open even when locked. Decide on locking, access control and any second security line at design stage.
• No service plan. Frameless leaves show sag and wear quickly. A six-monthly service catches carriage and roller wear before the glass edge starts to rub.

Servicing frameless automatic sliding doors

Frameless leaves show any sag immediately along the bottom edge of the glass, so the running gear matters. Each service checks the carriages, rollers and clamp rail fixings, the floor guide, the leaf level and the gaps to the fixed panels, the sensors and the opening and closing force. Our standard interval is every six months, and more often for high-traffic entrances. Our guide to the automatic door track and rollers explains what wears in the header.

We also service and repair frameless automatic sliding doors installed by others. Clamp rails and carriages differ between makes, so we identify the hardware on the first visit and confirm parts before we quote.

Frameless glass terms, explained

• Toughened glass. Glass heat-treated to be several times stronger than ordinary float glass; it breaks into small granules rather than sharp shards.
• Laminated glass. Two or more sheets bonded with an interlayer that holds the pieces together if the glass breaks.
• Clamp rail. The aluminium profile that grips the top edge of the glass and connects it to the carriages.
• Fixed panel (sidelight). A non-moving glass panel beside the sliding leaf.
• Manifestation. Markings on the glass that make it visible.
• Bi-parting. Two leaves that open from the centre in opposite directions.

Frameless automatic sliding doors: quick answers

• Frameless automatic sliding doors use toughened safety glass held by a top clamp rail and guided at the floor.
• Frameless automatic sliding doors on the MC-125 run single leaves up to 150 kg or bi-parting leaves up to 2 × 120 kg.
• Frameless automatic sliding doors need manifestation so people can see the glass.
• Frameless automatic sliding doors are slightly less tight against draughts than framed doors.
• Frameless automatic sliding doors are quoted per opening because the glass is made to size.
• Frameless automatic sliding doors are serviced every six months as standard, more often on busy entrances.

Frameless automatic sliding doors questions

Planning a frameless entrance? Request a quote with the opening size, a photograph and how busy the entrance is, or call us on 010 412 0062, Monday to Thursday 08:00 to 16:30 and Friday 08:00 to 14:00.