The short answer
Look for a marking etched or printed in a corner of the pane. It usually names the product standard, such as BS EN 12150 for toughened glass or BS EN 14449 for laminated glass, and an impact class. If there is no mark, an edge view, a polarised-light check or a glass thickness gauge can help, but only the marking or the manufacturer's paperwork confirms a security rating.
What does a safety marking say?
Safety glass marks vary by maker but usually include:
- The manufacturer or processor's name or mark
- The standard the glass meets, for example BS EN 12150 for toughened or BS EN 14449 for laminated
- A BS EN 12600 impact class such as 1(B)1 or 1(C)1
- On older glass, a BS 6206 class A, B or C
What do the letters in the class mean?
In a BS EN 12600 class such as 2(B)2, the letter shows how the glass breaks. B means the pieces stay held together, which is typical of laminated glass. C means the glass breaks into many small pieces, which is typical of toughened glass. The numbers show the impact height the glass withstood, with 1 the highest.
What if there is no marking?
- Look at an exposed edge of single glazing: laminated glass shows a fine line where the interlayer sits between the sheets
- Look through polarised sunglasses at an angle: toughened glass often shows a faint pattern of dark marks from the toughening process
- Ask a glazier to use a glass thickness gauge, which reads each pane in a sealed unit and can show whether one is laminated
- Check old invoices or the window maker's paperwork
Does a safety mark mean the glass is security glass?
No. A safety class tells you how the glass behaves when someone falls against it; it says nothing about resistance to a deliberate attack. Security-rated laminated glass carries a separate BS EN 356 class, such as P2A or P6B, in its marking or paperwork. Toughened glass on its own cannot hold a BS EN 356 class.
Why does it matter?
Insurers, landlords and buyers sometimes ask what glass is fitted, and the answer affects safety in doors and low windows as well as security. If you are not sure, our free survey for new installations includes checking the existing glass, so any recommendation starts from what is really there.
Sources
- Approved Document K: protection from falling, collision and impact (GOV.UK)
- BS EN 356:2000 Glass in building. Security glazing. Resistance against manual attack (BSI)
This guide is general information, not legal advice. Rules differ between England, Wales, Scotland and Northern Ireland; check with your council, building control or insurer where it matters.
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