Approved Document K in plain English
Part K of the Building Regulations covers protection from falling, collision and impact. In practice that means stairs, ramps, guarding, balustrades, low windows and vehicle barriers. This page sets out what it actually requires, including three figures that are widely published wrong.
What Part K covers
- K1 Stairs, ladders and ramps
- K2 Protection from falling, which is guarding and balustrades
- K3 Vehicle barriers and loading bays
- K4 Protection against impact with glazing
- K5 Protection from collision with open windows and similar
- K6 Protection against impact from and trapping by doors
Approved Document K is guidance, not law. The law is Part K of Schedule 1 to the Building Regulations 2010, which sets out what has to be achieved rather than how. Following the Approved Document is the straightforward route to showing compliance, and a different solution is allowed if you can demonstrate it meets the requirement. In practice, on a domestic job, follow the document.
Stairs: rise, going, pitch and 2R+G
A private stair in a single dwelling takes a rise between 150mm and 220mm, a going between 220mm and 300mm, and a maximum pitch of 42 degrees. Utility stairs take a rise of 150mm to 190mm with a going of 250mm to 400mm. General access stairs, the main route in a public building, take 150mm to 170mm with the same going range.
On top of those, twice the rise plus the going must land between 550mm and 700mm for every stair type. Every rise in a flight must be equal, and so must every going.
Check a stair against all four limits with the calculator.
Guarding: the 900mm and 1100mm confusion
This is the single most commonly misquoted figure in Part K, so it is worth being precise.
| Location | Minimum guarding height |
|---|---|
| Stairs, landings and ramps in a dwelling | 900mm |
| Edges of internal floors in a dwelling | 900mm |
| External balconies | 1100mm |
| Edges of roofs | 1100mm |
The line that gets crossed is the edge of an internal floor. A galleried landing overlooking a hallway, or the open edge of a mezzanine in a house, is guarded at 900mm. It is not a balcony and it does not take the 1100mm figure, despite how often that is published.
The 100mm sphere, and why spacing is not the test
In a building that children under five will use, guarding must not allow a 100mm sphere to pass through any opening, and it must not be easily climbable. Note that this is a sphere test, not a measurement between baluster centres. A 100mm gap between centres on 20mm balusters leaves an 80mm opening and passes. The same centres on 5mm wire leaves 95mm and also passes, but horizontal wires raise the climbability question instead.
The climbability requirement has no number attached to it. It is a judgement, and a building control officer will make it. Horizontal rails a child can use as a ladder are the usual point of disagreement.
Glazing: K4 and the critical locations
Glazing in a critical location has to break safely, be robust enough not to break, or be permanently protected. Critical locations are the parts of a building someone is likely to walk into: glazing in a door and within 300mm of the door edge up to 1500mm from floor level, and glazing in a wall below 800mm from floor level.
In practice that means toughened or laminated glass, marked with a kitemark you can see after installation. The mark matters, because an inspector cannot verify unmarked glass on site.
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Frequently Asked Questions
What is Part K of the building regulations? Part K covers protection from falling, collision and impact. It is the part that governs stairs, ramps, guarding and balustrades, vehicle barriers, safety glazing and protection from doors and windows.
What height should a balustrade be in a house? 900mm for stairs, landings, ramps and the edges of internal floors in a dwelling. 1100mm applies to external balconies and the edges of roofs. The 1100mm figure is frequently misapplied to internal landings.
What is the maximum gap in a balustrade? A 100mm sphere must not pass through any opening in guarding where children under five will use the building. It is a sphere test through the gap, not a measurement between baluster centres.
Is Approved Document K law? No. The law is Part K of Schedule 1 to the Building Regulations 2010. The Approved Document is statutory guidance showing one way to comply. You may use another approach if you can demonstrate it meets the requirement.
When was Approved Document K last updated? The current edition is the 2013 edition, which brought stairs, ramps, guarding, glazing and impact protection into one document. Always check gov.uk for amendments before relying on any figure.
Related calculators and guides
Sources
- Approved Document K, Protection from falling, collision and impact, 2013 edition, HM Government. Free under the Open Government Licence.
- Building Regulations 2010, Schedule 1, Part K.
