Toughened glass is heat treated so that it is much stronger than ordinary glass and breaks into small, blunt pieces. Laminated glass bonds layers of glass to a plastic interlayer, so it cracks but the pieces stay held in place. Both count as safety glass. Toughened suits doors and low-level panes; laminated suits overhead glazing, guarding, security and noise control.
What is toughened glass?
Toughened glass, also called tempered glass, is ordinary float glass that has been cut to size, edge-worked and then heated and cooled under control. The process leaves the surfaces in compression and the core in tension, which makes the pane considerably stronger and more resistant to heat than annealed glass of the same thickness.
The European product standard for this glass in buildings is BS EN 12150-1, currently published by BSI as BS EN 12150-1:2015+A1:2019. It covers flat, single-pane thermally toughened soda lime silicate safety glass, including its fragmentation behaviour, tolerances, flatness and edgework.
Because the stresses locked into the glass are what make it strong, toughened glass cannot be cut, drilled or notched after toughening. Any holes, cut-outs or shaped edges have to be made first, which is why every toughened pane is made to order for its exact opening.
What is laminated glass?
Laminated glass is made by bonding two or more panes together with a plastic interlayer under heat and pressure. The most common interlayer is PVB (polyvinyl butyral), though other interlayers are used for structural, acoustic or decorative purposes. The glass layers can be ordinary annealed glass, heat strengthened glass or toughened glass.
In the UK and Europe, laminated glass and laminated safety glass for buildings are covered by BS EN 14449, which sets out how the product's conformity is evaluated and how manufacturers control production. When laminated glass breaks, the interlayer holds the fragments together, so the pane usually stays in its frame as a cracked but intact barrier.
How do toughened and laminated glass break?
The test that sorts flat glass by impact performance is the pendulum test in BS EN 12600. It classifies how glass breaks into three types. Type A is the pattern typical of annealed glass, with sharp, separate pieces. Type B is typical of laminated glass, where the pieces stay held together. Type C is typical of toughened glass, which breaks into many small, relatively harmless pieces.
BS EN 12600 also grades impact resistance using drop heights of 190mm, 450mm and 1200mm, giving classes 3, 2 and 1, with class 1 the most demanding. A classification is written as a number, a letter and a number, such as 1(C)1 for a toughened pane or 2(B)2 for a laminated one, so the code tells you both how strong the glass is and how it breaks.
The practical difference is what happens after the break. Toughened glass leaves an empty opening once the pieces fall away. Laminated glass leaves a cracked panel in place, which keeps out weather and intruders until it is replaced and stops pieces falling from height.
| Feature | Toughened glass | Laminated glass |
|---|---|---|
| How it is made | Float glass heated and cooled under control to build in surface compression | Two or more panes bonded to a plastic interlayer such as PVB |
| How it breaks | Into many small, relatively blunt pieces (BS EN 12600 Type C) | Cracks but pieces stay bonded to the interlayer (BS EN 12600 Type B) |
| After breaking | Opening is left empty once pieces fall away | Cracked pane usually stays in the frame |
| Product standard | BS EN 12150-1 | BS EN 14449 |
| Cutting after manufacture | Not possible; made to exact size | Laminated annealed glass can be cut; toughened layers cannot |
| Typical uses | Doors, side panels, low-level panes, shower screens, splashbacks | Roof glazing, balustrades, security glazing, acoustic glazing |
| Spontaneous breakage | Small risk from nickel sulphide; reduced by heat soaking to BS EN 14179-1 | Depends on the glass layers used; interlayer retains pieces |
Where is each type of safety glass used?
Toughened glass is the usual choice for glazed doors, panels beside doors and low-level window panes, where the aim is to stop people being cut if they fall against the glass. Its strength and heat resistance also suit shower screens, glass splashbacks, frameless glass doors and many partitions.
Laminated glass is chosen where the glass must stay in place after breaking. That includes roof glazing, roof lanterns and other sloping overhead glazing, where falling glass is a risk, as well as glass used as guarding, such as balustrades. It is also used for security in ground-floor windows and shopfronts, and acoustic grades are used to reduce traffic noise.
The two are often combined. Laminated toughened glass bonds two toughened panes with an interlayer, giving the strength of toughened glass with the post-breakage retention of laminated glass. It is common in structural glazing, frameless balustrades and glass floors, where design is a matter for a specialist.
- Doors and door side panels: toughened or laminated
- Low-level window panes: toughened or laminated
- Shower screens and splashbacks: toughened
- Roof glazing and lanterns: laminated, often as the inner pane
- Balustrades: laminated, often laminated toughened
- Security and noise reduction: laminated
Which rules say where safety glass is required?
Building regulations across the UK require glazing in places where people are likely to collide with it to be safe, but the guidance differs between nations. In England, Approved Document K accepts glass meeting Class 3 of BS EN 12600 or Class C of BS 6206 in critical locations, and Class 2 or Class B for doors and door side panels with a pane wider than 900mm.
In Wales, glazing safety guidance sits in Approved Document N, which refers to the BS 6206 classes. In Scotland, the domestic technical handbook says glazing in these locations should be designed to resist human impact as set out in BS 6262-4. In Northern Ireland, Technical Booklet V gives guidance on the regulation covering impact with glazing. Both toughened and laminated glass can meet these requirements when correctly classified.
How can you tell whether glass is toughened or laminated?
Look for a mark in one corner of the pane. Safety glass is normally etched or printed with a permanent mark that stays visible after fitting. It usually identifies the manufacturer or processor, the product standard, such as BS EN 12150 for toughened or BS EN 14449 for laminated, and often the BS EN 12600 impact classification. Older glass may carry a BS 6206 mark instead.
If there is no mark, it may still be safety glass, but it cannot be confirmed by eye. Laminated glass can sometimes be identified by the faint line of the interlayer when the edge is visible. Where glass in a door or low-level panel is unmarked and its type is unknown, the safe course is to treat it as ordinary glass and replace it with marked safety glass.
What is heat-soak testing, and when does it matter?
Toughened glass can occasionally break without any obvious impact. One recognised cause is a tiny nickel sulphide inclusion formed during glass manufacture. After toughening, the inclusion can slowly change form and expand, and if it sits in the tensioned core of the pane it can shatter the glass months or years after installation.
Heat-soak testing reduces that risk. Toughened panes are heated in an oven and held at temperature for a set period so that panes with critical inclusions break in the factory rather than on site. The process is defined in BS EN 14179-1:2016. It is statistical: the standard's target is no more than one breakage per 400 tonnes of heat soaked glass, so the risk is reduced rather than removed.
Heat soaking matters most where a spontaneous break would be dangerous or costly, such as balustrades, overhead and roof glazing, large facade panels and glass at height. In those situations it is often combined with lamination, so that a broken pane stays in place. If your project includes toughened glass in any of these positions, ask whether heat soaking is included in the specification.
Which should you choose?
Choose toughened glass where the main need is safe breakage and strength at a sensible cost, such as doors, side panels, low-level panes, shower screens and splashbacks. Choose laminated glass where the glass must stay in place, where security or noise matters, or where it is overhead. Where both strength and retention matter, laminated toughened glass is the usual answer.
Our glaziers specify the glass for each pane at survey and list it on the written quote, including which panes are safety glass and to which standard, so you can see what will be fitted and why. Manufacturer guarantees apply to new glass, and the terms are confirmed in writing.
Frequently asked questions
Is toughened or laminated glass safer?
Each is safer in different situations. Toughened glass breaks into small, blunt pieces, which reduces cuts if someone falls against a door or low-level pane. Laminated glass holds together when broken, which matters overhead, as guarding or for security. Both are classed as safety glass when tested to BS EN 12600, and the right choice depends on the location.
Can toughened glass break on its own?
Occasionally, yes. Toughened glass can break without obvious impact because of edge damage, stress in the frame or a nickel sulphide inclusion in the glass. Heat-soak testing to BS EN 14179-1 reduces the inclusion risk but does not eliminate it. Where a sudden break would be dangerous, such as overhead or in a balustrade, laminated glass is normally used as well.
Can safety glass be cut to size on site?
Toughened glass cannot be cut, drilled or shaped after it has been toughened, so it is ordered to exact sizes with any holes made beforehand. Laminated glass made from ordinary annealed glass can be cut by a glazier, which is one reason it is sometimes used for repairs. Laminated glass made from toughened layers must also be made to size.
Do I need safety glass in my front door?
Yes, in practice. Glazing in doors falls within the critical locations described in the safety glazing guidance for England, Wales and Scotland, and Northern Ireland has its own glazing rules, so glass in a front door should be toughened or laminated safety glass, or otherwise meet the guidance. This applies to the glass in composite, uPVC, aluminium and timber doors, as well as to side panels next to the door.
Does laminated glass reduce noise?
Laminated glass can help, and acoustic laminates use an interlayer designed specifically to damp sound. Using panes of different thicknesses in a double glazed unit also helps. The overall result depends on the whole window, including the frame and seals, so acoustic glass is most effective as part of a window specified for noise reduction.
Sources
- BS EN 12150-1:2015+A1:2019 Thermally toughened soda lime silicate safety glass – BSI
- BS EN 14449:2005 Laminated glass and laminated safety glass – BSI
- BS EN 12600:2002 Pendulum test: impact test method and classification for flat glass – BSI
- BS EN 14179-1:2016 Heat soaked thermally toughened soda lime silicate safety glass – BSI
- BS 6262-4:2018 Glazing for buildings: code of practice for safety related to human impact – BSI
- Approved Document K: Protection from falling, collision and impact – GOV.UK
- Approved Document N: glazing (safety in relation to impact, opening and cleaning) – GOV.WALES
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