Approved Document N (Glazing Safety): What Homeowners Need to Know

Part N requires that glazing in critical locations is either:

• Made from a safe breakage material (toughened glass to BS EN 12150, laminated glass to BS EN 12543, or glass blocks), OR
• Small panes (maximum dimension 250 mm, maximum area 0.5 m² of annealed glass at least 6 mm thick), OR
• Permanently protected by a robust barrier that prevents people from touching the glass.

The safety glass must be marked with its EN standard and performance class; always ask your glazing supplier for confirmation that the glass meets BS EN 12150 (toughened) or BS EN 12543 (laminated).

Critical locations as defined in Approved Document N are:

• Glazing in doors: all glazing in doors (and in door side panels within 300 mm of the door edge) that is less than 1,500 mm from floor level
• Low-level glazing in windows: glazing in a window where any part of the glass is less than 800 mm from floor level
• Glazing in bathrooms: glazing less than 1,500 mm from floor level adjacent to a shower or bath
• Glass balustrades and barriers: all glass used as a balustrade or structural barrier

These are the locations where people are most likely to accidentally walk into or fall against glass.

There are two main types of safety glass used in buildings:

• Toughened (tempered) glass: heat-treated to be approximately five times stronger than ordinary glass. If it does break, it shatters into small, relatively harmless cubes rather than dangerous shards. This is the most common type in windows and doors.
• Laminated glass: two or more panes bonded with a plastic interlayer (typically PVB). When broken, the fragments stay adhered to the interlayer rather than falling away. Laminated glass is preferred where fragments falling from height could cause injury (e.g. overhead rooflights, glass floors).

Both types are acceptable under Part N; the choice between them depends on the application and the additional requirements of Part K (guarding).

For glazed extensions (orangeries, garden rooms) and roof glazing:

• All roof glazing must use laminated safety glass (not toughened) to prevent falling fragments injuring people below if a pane breaks.
• Glass in the walls of an extension at low level (below 800 mm) must be safety glass.
• Any glass panel forming a structural balustrade (e.g. on a raised deck or glazed side panel) must be safety glass, and the structural adequacy must comply with Part K.

Building control will check that glazing in critical locations has been installed correctly, typically by asking for the glazing specification and checking for the British Standard mark on the glass. During a site inspection, the BCO may look for the CE or UKCA mark and BS EN number etched into the corner of the glass. If you cannot demonstrate compliance, the glass may need to be replaced.