Toughened vs laminated glass: which one goes where

Most people only think about the type of glass when a pane has broken and the glazier asks which one they want. Here is the short answer, then the detail behind it.

The short answer

• Toughened glass for anywhere a person could fall against or walk into the glass: doors, the panels beside them, low windows, shower screens, shelves, table tops and kitchen splashbacks.
• Laminated glass for anywhere the pane must stay in place once it is broken: shopfronts, street-level windows you want more secure, the inner pane of a rooflight, and glass on a busy road where noise is the problem.
• Ordinary float glass only where neither applies, such as the upper panes of a sash window or small panes well above floor level.

Not sure what you have now? Photograph a corner of the pane and send it to us on WhatsApp, or ring 07915 903485, and we will tell you what is there and what should replace it.

Three kinds of glass, three ways of breaking

Float glass is the plain sheet that every other type starts from. It is clear, cheap and can be cut on the bench in minutes. Its weakness is the way it fails: it breaks into long, pointed shards that can cut badly.

Toughened glass is float glass that has been cut to its final size, heated almost to softening and then cooled fast with jets of air. That leaves the surface in compression, which makes the pane far stronger than the sheet it came from and able to cope with heat beside a hob. When it does break, it crumbles into small, blunt granules rather than daggers. The catch: nothing can be done to it afterwards, and a deep chip on an edge can make the whole pane let go without warning.

Laminated glass is two or more sheets bonded to a clear plastic interlayer. Hit it and it cracks, but the fragments stay stuck to the interlayer and the pane stays in the frame. Thicker interlayers give more security; special acoustic interlayers cut traffic noise. Because it is only glass and plastic, a sheet can still be cut to size in the workshop.

Where the rules say safety glass

Building Regulations treat certain places as critical locations, where safety glass is expected: glass in and around doors, and glass low enough that someone could walk or fall into it. Most modern doors and patio screens already meet this. Older London houses often do not. Victorian and Edwardian terraces across Haringey and Islington still have plain float or old wired glass in back doors, kitchen doors and the low panes of bay windows. Wired glass looks reassuring, but the wire is there to hold the pane together in a fire, not to make it safe to fall against.

If one of those panes breaks, replace it with safety glass rather than matching what was there. FENSA covers replacement windows and doors, not a new pane in an existing frame, so a glass-only repair needs no certificate.

Room by room in a typical London home

• Front and back doors: toughened, or laminated if the door faces a quiet side return or alley and security matters more. Obscure or satin-finish versions give privacy in a hallway.
• Basement and ground-floor windows on the street: a laminated inner pane makes a double glazed unit much harder to get through, which suits garden flats and lower-ground flats in Camden and Islington.
• Sash windows: the lower sash is often low enough to need safety glass; the upper sash rarely is. Slim units and single glazing can both be made in either type.
• Bathrooms and kitchens: toughened for shower screens and splashbacks, obscure toughened for a bathroom window you can lean against.
• Rooflights, roof lanterns and glass roofs: a laminated inner pane, so that a broken pane cannot fall into the room below.
• Balustrades and Juliet balconies: toughened laminated, which combines the strength of one with the hold of the other.
• Shopfronts on the high street: laminated, so that a smashed pane on Green Lanes or Holloway Road overnight is a cracked pane in the morning, not an open shop. See our shopfront glazing page for commercial work.

Mixing types in a double glazed unit

A sealed double glazed unit is two panes with a spacer between them, and each pane can be chosen separately. A common pairing is toughened outside and laminated inside, or toughened both sides in a door. That matters when a unit mists up: the new unit fitted in your existing frame can carry better glass than the one it replaces. Our page on misted double glazing repair explains how a unit is swapped without a new window.

Mistakes worth avoiding

• Asking for toughened glass to be trimmed. It cannot be. Measure carefully, or let us measure, because a panel made a few millimetres out has to be made again.
• Putting float glass back in a door because that is what came out of it.
• Assuming toughened means secure. It is strong, but once broken it leaves nothing behind.
• Leaving a cracked toughened pane in place. It can finish breaking at any moment; tape it and keep people clear until it is replaced.

Getting the right glass cut or fitted

Stock float glass is often cut at our Wood Green workshop while you wait. Toughened panels, and laminated in the less common thicknesses, are made to order once the sizes are confirmed. Send the measurements, or ask for a survey, through our glass cut to size page, and you get one fixed price before anyone cuts a sheet or gets in the van.

If the glass has already broken and the house or shop is not secure, our emergency glazing team answers around the clock across Central and North London. We are rated 4.7 on Google (36 reviews).