Staircase guarding and balustrade: height and the 100mm rule
Written by Scott Jones, The Stair Guys, independent staircase measuring and sourcing specialists·Last updated
Guarding, the balustrade, is what stops a fall from the side of a stair or a landing. The rules cover three things: where you need it, how high it has to be, and how big a gap it can have.
Where guarding is needed
You need guarding anywhere there is a drop people could fall from: the open side of a flight, the edges of landings, and any floor-level edge such as a stairwell opening. If there is a drop, it needs protecting.
Height: 900mm in a home
In a house, guarding to a stair and its landings must be at least 900mm high, measured from the pitch line on the flight and from the floor on a landing. Scotland is the one to watch: it uses 840mm on the flight itself, while other locations stay higher. That kind of four-nation difference is exactly what catches people who apply England figures to a Scottish job.
The 100mm sphere rule
No gap in the guarding may be large enough to let a 100mm sphere pass through, so no opening more than about 99mm anywhere, between spindles, under the bottom rail, or beside a newel. It is often called the child-safety rule, but it applies whether or not there are children in the house. On top of that, guarding in a home should not be built so that a young child can easily climb it. Both of these are as much about how the balustrade is made as its height.
For the full set of figures across England, Wales, Scotland and Northern Ireland, see our guide to UK staircase building regulations.
Frequently asked
How high does staircase guarding have to be?+
In a home, at least 900mm, measured from the pitch line on the flight and from the floor on a landing. Scotland uses 840mm on the flight itself, which is a common four-nation catch.
What is the 100mm gap rule for stairs?+
No gap in the guarding may be large enough to pass a 100mm sphere, so nothing over about 99mm, whether between spindles, under a bottom rail or beside a newel. It applies whether or not there are young children in the house.
Where do you need guarding on a staircase?+
Anywhere there is a drop someone could fall from: the open side of the flight, the edges of landings, and floor-level edges such as a stairwell opening. If there is a drop, it must be guarded.
Does stair guarding have to be child-safe if I have no children?+
Yes. The 100mm sphere rule and the guidance that guarding should not be easily climbed by a young child apply regardless of who lives there, because homes change hands and are visited by children.
Related guides
- UK Staircase Building Regulations, ExplainedThe building regulations for stairs in England, Wales, Scotland and Northern Ireland, in plain English. Rise, going, pitch, headroom, guarding and handrails, every figure sourced.
- Staircase headroom: how much you need and how to check itHow much headroom a staircase needs under UK building regulations: the 2 metre rule, the reduced loft-conversion allowance, where headroom is tightest, and how to check it properly.
- Staircase handrail requirements: height, sides and gripWhat UK building regulations require of a staircase handrail: the 900mm to 1000mm height, when you need one side or both, and why a wall-mounted rail needs proper clearance and grip.
- Private staircase dimensions: rise, going and pitchThe rise, going and pitch rules for a private (domestic) staircase in the UK, the 2R+G formula, why every rise must be equal, and the simple going = rise divided by 0.9 rule of thumb that keeps a stair within 42 degrees.
- Staircase building regulations: Northern IrelandThe staircase building regulations for Northern Ireland under Technical Booklet H (2012): rise, going, pitch, risers per flight, width, headroom, handrails and guarding, and how they differ from England, Wales and Scotland.
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