Automatic Door Glass: Types, Thickness and Weight

Automatic door glass decides more about an entrance than most people realise. It sets the weight the operator has to move, how the door behaves when it is broken, how secure the entrance is overnight, how much heat comes through a west-facing shopfront, and a large part of the price. The operator gets most of the attention, but automatic door glass is usually the heaviest and most expensive part of the leaf.

This guide explains which glass is used in automatic doors, how thick it usually is, how to work out what a leaf weighs, how framed and frameless doors differ, and what to decide before you ask for a quote. It uses the published limits for our MC-125 sliding door operator and MCW-100 swing door operator.

What glass is used in automatic doors?

Automatic door glass is always safety glass. Ordinary annealed float glass breaks into large, sharp pieces, so it is not used in doors or in the panels beside them. Safety glazing in doors is covered by SANS standards published by the South African Bureau of Standards. The glazier confirms the type and thickness for the leaf size and position, and your building or fire consultant confirms what applies to the particular entrance. We supply and commission the automation; we do not certify glazing.

In practice, automatic door glass is one of four types:

• Toughened glass. Heat-treated so it is much stronger than ordinary glass. When it breaks, it breaks into small, blunt pieces. It cannot be cut or drilled after toughening, so every hole and notch is made first.
• Laminated glass. Two or more sheets bonded with a plastic interlayer. When it breaks, the pieces stay stuck to the interlayer and the pane stays in the frame. Better for security, and it can be cut to size.
• Toughened laminated glass. Toughened sheets laminated together. The strength of toughened glass with the hold-together behaviour of laminated. Common on large frameless leaves and where security matters.
• Insulated glass units. Double glazing, with two panes and a sealed gap. Better for heat and noise, but thicker and heavier, so they are normally used in framed leaves.

Automatic door glass thickness

There is no single right thickness. Automatic door glass is chosen for the size of the leaf, how it is held, how exposed it is to wind, and how secure it has to be. As a general guide:

• Framed leaves use thinner glass, because the aluminium frame carries the hardware and supports every edge. Laminated glass such as 6.38 mm, or toughened glass of a similar thickness, is a common choice.
• Frameless leaves use thicker toughened glass, often 10 or 12 mm, because the glass is held only at the top and has to be the structure of the leaf.
• Insulated units in framed leaves are thicker overall, because they contain two panes and a gap.

The thickness for your door is confirmed by the glazier against the leaf size and the site. On exposed coastal entrances, wind load can push the thickness up. Our guide to frameless automatic sliding doors covers frameless glass in more detail.

How to work out what a leaf weighs

The weight of automatic door glass is easy to estimate. Glass weighs about 2.5 kg per square metre for every millimetre of thickness, and toughening or laminating does not change that much. Multiply the area of the leaf by the thickness and by 2.5.

• A leaf 1,200 mm wide and 2,400 mm high is 2.88 m² of glass.
• In 6.38 mm laminated glass that is about 46 kg.
• In 10 mm toughened glass, about 72 kg.
• In 12 mm toughened glass, about 86 kg.
• In a double-glazed unit with two 6 mm panes, about 86 kg.

These are estimates for planning. The glazier’s figure for the actual build-up is the one that goes on the order, because interlayers, coatings and edge work add a little weight. Then add the frame, or for a frameless door the top clamp rail and fittings. That total is the leaf weight the operator has to drive, and it is the first figure we work out on any automatic door glass specification.

Leaf weight and the operator

Once the weight of the automatic door glass is known, it has to sit inside what the operator is rated for.

• MC-125 sliding door operator: up to 150 kg on a single sliding leaf, or 2 × 120 kg on a bi-parting door. Leaf widths run 750 to 1,600 mm single and 650 to 1,250 mm per leaf bi-parting.
• MCW-100 swing door operator: up to 150 kg and up to 1,200 mm wide, but the two limits interact, and the figures were tested without wind pressure.

Most leaves sit comfortably inside those limits. The ones that do not are very large single leaves in thick glass. A single leaf 1,600 mm wide and 3,000 mm high in 12 mm glass is 4.8 m², or about 144 kg before the rail and fittings are added, which takes it to the limit of a single slide. The answer is usually to split the opening into a bi-parting pair, which halves each leaf’s weight and its travel. See the MC-125 sliding door operator and our guide to automatic door operator size.

Framed or frameless automatic door glass

The biggest decision about automatic door glass is whether the leaf has a frame at all.

• Framed leaves hold the glass in an aluminium frame. The frame carries the lock, seals and hardware, supports every edge of the glass, and allows thinner glass, laminated glass or double glazing. Framed doors are usually more secure, seal better against wind and dust, and cost less to reglaze.
• Frameless leaves clamp thick toughened glass at the top and guide it at the bottom. They look lighter and more open, and they suit showrooms, hotel lobbies and corporate receptions. The glass is heavier, the edges are exposed and replacing a broken leaf takes longer.

Neither is better in every case. Framed automatic door glass is the practical choice for exposed, busy or security-sensitive entrances. Frameless is a design choice for entrances where the view through the glass matters most. See automatic sliding doors for both layouts.

Automatic door glass and security

An automatic glass entrance is not a security barrier, but the choice of automatic door glass changes how much delay it offers. Toughened glass is strong, but once broken it falls out of the opening. Laminated glass stays in place when broken and has to be cut or forced through, which takes time and makes noise. For a jeweller, pharmacy or electronics shop, laminated or toughened laminated glass in a framed leaf is the usual recommendation. Our guide to automatic door security explains how glass, locking and what sits behind the entrance work together.

Heat, sun and glare

South African sun puts automatic door glass under real heat load, especially on west-facing shopfronts in the afternoon. Clear glass lets the most heat and glare through. Tinted, reflective and solar-control glass reduce both, and insulated units also help keep a cooled lobby cool. Sun on glass also heats the leaf and the seals, and can make some motion sensors misbehave on hot afternoons. If an entrance faces west or north into strong sun, it is worth deciding the glass and a canopy together. See outdoor automatic doors and the South African climate.

Wind, coastal sites and dust

Wind loads automatic door glass while the leaf is moving and while it is closed. On the coast, in Cape Town, Gqeberha, Durban and East London, wind pressure and salt air both matter. Larger leaves may need thicker glass, and framed leaves with good seals are usually the better choice on exposed entrances. Inland, dust is the bigger problem, and a framed leaf with brush seals keeps more of it out of the building.

Fixed panels, sidelights and fanlights

Automatic door glass is not only in the moving leaves. Most sliding entrances have fixed panels on either side, and many have a fanlight or panel above the header. These are part of the same entrance and should be specified as safety glass to the same standard as the leaves, because people walk into them as easily as into the door. Mark them with the same manifestation as the moving leaves so the whole entrance reads as glass. Our automatic door signage guide covers manifestation heights.

When automatic door glass breaks

Breakage is the moment the choice of automatic door glass matters most. Toughened glass shatters into small pieces and leaves an open hole, so the entrance has to be closed off or boarded until the new leaf arrives. Laminated glass cracks but stays in the frame, so the entrance is usually still secure, though the leaf must be replaced.

Toughened glass is made to size and cannot be cut afterwards, so a replacement leaf is ordered to the exact measurements. Laminated glass can often be cut from stock. If a leaf breaks, switch the door off at its isolator, keep people away from the opening, and call us. See automatic door repairs.

Glass in swing doors

Swing doors put different demands on the glass. The leaf is hung on hinges or pivots rather than carried on a track, so its weight acts on the hinge side and on the operator arm every time it opens. A heavy leaf also carries more momentum as it swings, which is why doors near the MCW-100’s limits should run at reduced speed.

Framed swing leaves with laminated or toughened glass are the usual choice. Frameless glass swing doors need the correct glass-clamp arrangement for the operator arm, and that is confirmed before the glass is ordered. See the MCW-100 swing door operator.

Edges, fittings and finger traps

On a framed leaf the edges of the glass are hidden in the frame. On a frameless leaf they are exposed, so they are polished, and the gaps between moving and fixed glass are set so that fingers cannot be caught as the leaf passes a fixed panel. Patch fittings, clamp rails and floor guides are fixed through holes and notches that must be made before the glass is toughened. That is why frameless leaves are measured on site and drawn before anything is ordered: a hole in the wrong place cannot be corrected afterwards.

Cleaning and looking after the glass

Glass on an automatic entrance gets dirty quickly, and the cleaning routine matters for more than appearance. Cleaners should switch the door to a hold-open or off mode while they work, rather than standing in the sensor field. Use cleaning products that suit any coating on the glass, keep water and detergent out of the floor guide, and do not spray sensors directly. A clean sensor lens and a clean floor guide prevent many of the faults we are called out for.

Automatic door glass and the price

Glass is one of the biggest variables in what an automatic door costs. Thicker glass, laminated or toughened laminated build-ups, solar-control coatings and insulated units all add to the price, and frameless leaves need precise fabrication. The operator price changes far less from one job to another than the glass does. Our automatic door prices guide explains how a quotation is built up.

Glass and aluminium in one package

An automatic door almost never arrives on its own. It sits in a shopfront, screen or frame, and on most projects the automatic door glass, the aluminium and the operator are quoted together. We handle the glass and aluminium around our automatic doors in-house, so one supplier is responsible for the leaf weight, the tolerances and the way the door runs. See automatic door systems.

Common automatic door glass mistakes

• Choosing the glass before working out the weight, then finding the leaf is too heavy for a single slide.
• Toughened glass on a security-sensitive shopfront where laminated would hold the opening after an attack.
• Clear glass on a west-facing entrance with no canopy, then complaints about heat and glare.
• Sidelights specified to a lower standard than the moving leaves.
• No manifestation, so people walk into the glass.
• Frameless on an exposed, windy entrance where a framed leaf would seal and last better.

What to send us

To specify automatic door glass properly, send us the opening size, photographs from inside and outside, which way the entrance faces, whether it is exposed to wind, what the building needs from the entrance at night, and whether you want framed or frameless. We will work out the leaf weight, suggest the glass build-up for the glazier to confirm, and match the operator to it.

Automatic door glass: quick answers

• Automatic door glass is always safety glass: toughened, laminated or both.
• Automatic door glass weighs about 2.5 kg per m² for every millimetre of thickness.
• Automatic door glass in framed leaves is thinner, often around 6 mm or 6.38 mm laminated.
• Automatic door glass in frameless leaves is thicker toughened glass, often 10 or 12 mm.
• Automatic door glass sets the leaf weight, which must suit the operator’s rating.
• Automatic door glass that is laminated stays in place when broken, which helps security.
• Automatic door glass type and thickness are confirmed by the glazier for each opening.

Automatic door glass questions

Planning a new glass entrance? Request a quote with the opening size and photographs, and we will work out the leaf weight and match the automatic door glass and operator to it. Glazing standards are published by the South African Bureau of Standards. We are on 010 412 0062, Monday to Thursday 08:00 to 16:30 and Friday 08:00 to 14:00.