Where does glass have to be toughened or laminated, and how do I tell?

Building regulations identify certain positions as critical locations: the places where a person is most likely to walk into glass or fall against it. Glazing in those positions has to break safely or not break at all. It is one of the few glazing rules that is genuinely about life and limb, and it is straightforward to check on your own house.

Safety

Step by step

1. Learn where the critical locations are.Broadly: the glazing in a door, and in any side panel close to the door edge, from floor level up to a height above shoulder level; and glazing in a wall below waist height, down to floor level. The exact heights and distances are set out in the building regulations guidance for your nation.
2. Check the current figures rather than a remembered number.The heights that define the bands are specific, they differ slightly between nations, and they have been revised over time. Look them up for your nation rather than working to a figure from an article.
3. Look for the etched mark.Safety glass carries a permanent mark, sandblasted or etched into one corner. It names the manufacturer, the standard the glass was made to, and a letter or word identifying the type. It is small, it is often at the very edge of the pane, and it is often hidden behind a bead or a gasket.
4. Look along the bottom edge of the pane too.On a sealed unit, the mark is on the outer surface of one pane, usually low down. Get level with the bottom of the glass and look at a shallow angle with a torch — the sandblasted mark shows up far better raking than head-on.
5. Use the polarised sunglasses test for toughened glass.Toughened glass viewed through polarised lenses at an angle shows a faint pattern of spots or stripes, caused by the stress pattern from the toughening process. Annealed glass shows nothing. It is not conclusive but it is a good field indicator.
6. Look at a cut edge for laminated glass.Laminated glass is two panes bonded to a plastic interlayer, and the interlayer is visible as a very fine line at any exposed edge. If you can see the edge of the pane, this is definitive.
7. Look for a heat-soak or safety marking on newer units.Modern replacement units carry markings on the spacer bar as well, giving the manufacturer and the date, which tells you the era and often the specification.
8. Decide what to do about a pane with no mark.If it is in a critical location and there is no mark, assume it is annealed and plan to replace it. Replacing a single pane in a door or side panel with a toughened or laminated unit is a routine, modest job for a glazier.
9. Choose between toughened and laminated deliberately.Toughened breaks into small blunt granules and is the usual choice for doors. Laminated holds together on the interlayer when broken, which is better where the glass also has a security or fall-protection role, or where the opening must not be left unglazed.
10. Specify safety glass whenever you replace anything in these positions.Even where nobody is checking, this is the cheapest safety upgrade available. The cost difference between annealed and toughened on a domestic pane is small.

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