Safety Glass Regulations UK: Where the Law Requires It, and What Counts
Safety glass regulations in the UK come down to two heights and one distance. Any glass between the floor and 800mm in a wall or window, and any glass between the floor and 1500mm in a door or within 300mm of one, is a critical location. There it has to break safely, be robust enough not to break, or be screened off. Everywhere else, ordinary glass is allowed. That single rule decides a surprising amount of interior design: glazed doors, internal screens, low windows and the glass beside a front door.
The rule: requirement K4 of the Building Regulations 2010, with the guidance in Approved Document K, 2013 edition, for use in England.
Walls and windows: critical from finished floor level up to 800mm.
Doors and side panels: critical from floor level up to 1500mm, in the door and in any panel within 300mm of either edge of the door.
What passes: Class 3 of BS EN 12600 or Class C of BS 6206, or Class 2 or Class B in a door or side panel wider than 900mm.
Why these zones, and not all glass
Approved Document K is candid about the reasoning. Doors and the panels beside them are where people push, stumble and put a hand out, especially when a door sticks, and an impact between waist and shoulder height can be followed by a fall through the glass. Away from doors the risk is low-level glass, where children are the most vulnerable. So the regulation targets exactly those areas and leaves glass above them alone.
The legal requirement itself is short. Requirement K4 says glazing that people are likely to come into contact with while moving in or about a building must either break in a way unlikely to cause injury, resist impact without breaking, or be shielded or protected from impact. The Approved Document is the government's guidance on how to meet it.
The three ways to comply
1. Glass that breaks safely
This is what most people mean by safety glass. A breakage counts as safe under BS EN 12600 and BS 6206 if it leaves only a small clear opening with small detached particles, disintegrates into small particles, or breaks into separate pieces that are not sharp or pointed.
| Where the glass is | What it must achieve |
|---|---|
| Any critical location | Class 3 of BS EN 12600, or Class C of BS 6206 |
| A door or door side panel with a pane wider than 900mm | Class 2 of BS EN 12600, or Class B of BS 6206 |
In practice that means toughened glass, which shatters into small blunt granules, or laminated glass, which cracks but is held together by its interlayer. Laminated is the better choice where you also want the pane to stay in place once broken, such as glass that is also acting as a barrier.
2. Glass that is robust, or in small panes
Some materials are strong enough that the risk of breakage is low: polycarbonate and glass blocks are the examples the guidance gives, and annealed glass gains strength through thickness, with limits on pane size set out for large shopfront style areas.
Small panes are the route for period joinery. A small pane of annealed glass can be used in a critical location if it is no more than 250mm wide and no more than 0.5 square metres in area, and at least 6mm thick. In traditional leaded or copper lights, where fire resistance does not matter, 4mm glass is acceptable. That is how an original Victorian door with small leaded panes can stay as it is.
3. A permanent screen
If glass in a critical location sits behind a permanent screen, the glass itself does not need to comply. The screen must stop a 75mm sphere touching the glass, be robust, and, if the glazing is there to stop people falling, be hard to climb, so no horizontal rails.
Room by room: where it catches people out
- Internal glazed doors. Every pane below 1500mm in the door is a critical location. A reclaimed door with large clear annealed panes will not comply as new work unless the glass is replaced or the panes are small enough.
- Glass beside a front door. Side lights within 300mm of the door edge are critical up to 1500mm, even if they look like windows.
- Crittall-style internal screens. Any panes below 800mm are critical, and so is everything below 1500mm if the screen incorporates a door or sits within 300mm of one.
- Low windows and floor-to-ceiling glazing. The bottom 800mm is critical. Where glass is also guarding a drop, the guidance treats it as containment below 800mm, which brings in the guarding rules as well.
- Glass balustrades. These are guarding as well as glazing. In a single family dwelling guarding on stairs, landings and internal floor edges should be at least 900mm high, and 1100mm on external balconies, including Juliet balconies. Our guide to staircase building regulations covers the rest.
- Bathrooms. A glazed bathroom door follows the door rule. Shower screens and enclosures are normally supplied in toughened safety glass; check the product is marked before it goes in, and see our guide to designing a bathroom for layout.
How to check the glass you have
Safety glass is normally marked with a small permanent stamp in one corner, giving the standard it meets. Toughened glass is usually marked to BS EN 12150 and laminated to BS EN 14449, and the stamp often also shows the BS EN 12600 impact class. No mark does not prove the glass is annealed, but it is a reason to ask your glazier. You cannot toughen glass after it has been cut, so a pane that needs to be safety glass has to be replaced, not treated.
Does this apply to my project?
Part K applies to building work: new build, extensions, and new or replacement windows and doors, which in England are normally installed by a FENSA or similar competent person scheme installer who self-certifies compliance. If you are altering a period home, our guide to building regulations for a London renovation explains which work needs building control, and our page on replacement window U-values covers the energy side of new glazing.
There are two extra rules that do not apply in homes. Manifestation, the marking of large clear glass so people do not walk into it, is requirement K5.2, and it does not apply to dwellings. Neither does K5.1 on collisions with open windows. They matter for a studio, shop or office fit-out but not for your kitchen extension.
Even where the regulations do not strictly bite, such as replacing a single pane in an existing internal door, using safety glass in a critical location costs little and is what any sensible glazier will recommend. If children live in or visit the house, treat it as non-negotiable.
Frequently Asked Questions
Where is safety glass required by building regulations?
In critical locations under Approved Document K: glazing between floor level and 800mm in walls and windows, and between floor level and 1500mm in doors and in side panels within 300mm of either edge of a door.
Do internal glass doors need to be safety glass?
Yes. Glazing in a door is a critical location from floor level up to 1500mm, so it must break safely, be robust or small-pane glazing, or be protected by a permanent screen. In practice that usually means toughened or laminated glass.
What class of safety glass is needed in a door?
Class 3 of BS EN 12600, or Class C of BS 6206, in any critical location. If the pane in a door or door side panel is wider than 900mm, the higher Class 2 of BS EN 12600, or Class B of BS 6206, is needed.
Can I keep old glass in a period door?
Existing glazing that you are not altering is not caught by new work rules. When glazing is new, small annealed panes can still comply if each is no more than 250mm wide and 0.5 square metres in area and at least 6mm thick, or 4mm in traditional leaded or copper lights where fire resistance does not matter.
How do I know if my glass is toughened?
Look for a permanent stamp in one corner naming the standard, usually BS EN 12150 for toughened and BS EN 14449 for laminated glass. If there is no mark, ask a glazier to check before relying on it.
Does glass need manifestation markings in a house?
No. Requirement K5.2 on manifestation of glazing does not apply to dwellings. It applies to other buildings, such as offices, shops and studios.
Sources
- Approved Document K: protection from falling, collision and impact (2013 edition), for requirement K4, Diagram 5.1 critical locations, the BS EN 12600 classes, small pane limits, permanent screens, guarding heights and the dwelling exemptions from K5.1 and K5.2
- FENSA, for self-certification of replacement windows and doors in England
Checked on 15 September 2026. Guidance applies to England. Wales and Scotland have their own building standards. Where glass also acts as guarding, confirm the design with building control or a structural engineer.