Staircase Regulations UK: Rise, Going, Pitch and Headroom

The six numbers that decide a UK staircase

Stairs in England and Wales are governed by Approved Document K of the Building Regulations, with near-identical rules in the Scottish Technical Handbooks and Northern Ireland's Technical Booklet H. The document is long, but for a normal domestic flight almost all of it reduces to a short list of dimensions. Everything else — nosing profile, tapered treads, guarding, alternating-tread stairs — is a variation on those dimensions rather than a separate set of rules.

Rise and going, and why they are linked

The rise is the vertical height from the top of one tread to the top of the next. The going is the horizontal distance from the nosing of one tread to the nosing of the next — not the width of the board, which includes the nosing overhang and is always larger. On a private stair the rise may be anywhere from 150mm to 220mm and the going must be at least 220mm, but the two are not independent: the 2R+G rule ties them together so that a tall rise forces a deeper going.

That rule exists because the pair of dimensions, not either one alone, determines whether a flight is comfortable. Twice the rise plus the going must land between 550mm and 700mm, and the comfortable middle of that band is around 600-640mm. A 190mm rise with a 250mm going gives 630mm and walks beautifully. A 220mm rise with a 220mm going gives 660mm — legal, but at 45 degrees it would exceed the pitch limit, which is exactly how the rules stop you from building it.

• Every rise in a flight must be equal, within a 5mm tolerance.
• Every going in a flight must be equal, with the same tolerance.
• The nosing must project no more than 25mm where treads overlap.
• Open risers must not allow a 100mm sphere through, and treads must overlap by at least 16mm.
• The minimum stair width is not specified for dwellings, but 800-900mm is the practical norm.

Pitch and headroom

The maximum pitch for a private stair is 42 degrees. There is no minimum, though a flight much below 30 degrees eats an unreasonable amount of floor. Pitch is arctan(rise ÷ going), so a 200mm rise on a 230mm going is 41 degrees and about as steep as a house stair is allowed to be. The stair pitch calculator will do the arithmetic and flag the limit; the stair rise and run calculator is the one to use if you are working backwards from a fixed floor-to-floor height.

Headroom is 2000mm measured vertically from the pitch line — the line joining the tread nosings — to the underside of whatever is above. The one relaxation worth knowing is for loft conversions: where the full 2000mm cannot be achieved, 1900mm at the centre of the stair width and 1800mm at the side is accepted. That concession is specific to a loft conversion and does not apply to a new-build flight.

Handrails, guarding and the 100mm sphere

A handrail is required on at least one side of any flight, and on both sides where the stair is wider than 1000mm. The height is 900mm to 1000mm measured vertically from the pitch line on the flight, and 900mm from the floor on a landing. Guarding — the balustrade itself — must be 900mm on the flight and 1100mm on landings in a dwelling.

The 100mm sphere rule governs every opening in that guarding: no gap may allow a 100mm sphere to pass. It applies between spindles, between the bottom spindle and the string, and to the triangular opening formed where a raking rail meets a tread and riser. Guarding must also be designed so children cannot readily climb it, which is why horizontal rails are discouraged in dwellings. The spindle spacing calculator works the gaps out from the clear run and flags anything over the limit.

Tapered treads, winders and landings

Winders are allowed in a private dwelling but they are measured differently. On a tapered tread the going is measured at the centre of the stair width where the flight is under 1000mm wide, and at 270mm in from each side where it is wider. The narrow end of a tapered tread must still be at least 50mm. Consecutive tapered treads must all have the same going, and a flight cannot mix a set of winders with an inconsistent turn.

Landings are required at the top and bottom of every flight, at least as long and as wide as the narrowest part of the stair. A door may swing over a landing at the bottom of a flight only if it leaves at least 400mm clear across the full width. No flight in a dwelling may have more than 36 risers without a change of direction.

What to check before you order

1. Measure the finished floor-to-floor rise, including both floor coverings.
2. Divide by 190mm to get a starting riser count, then round to a whole number.
3. Recalculate the exact rise and check it is between 150mm and 220mm.
4. Set the going from 2R+G and confirm it is 220mm or more.
5. Check the pitch is 42 degrees or less.
6. Multiply the going by the tread count and confirm the total run fits the opening.
7. Check 2000mm headroom at the trimmer, the tightest point on almost every stair.

Do those seven checks before anything is ordered and a building control visit becomes a formality. The two that catch people out are the headroom at the trimmer, which is fixed by the opening rather than the stair, and the total run, which is the reason so many replacement flights end up steeper than the one they replaced. If either fails, the answer is a landing or a quarter turn rather than a steeper riser.

Whatever you decide, get the numbers first: the stair runner calculator doubles as a stair runner length calculator, adding nosing wrap, landings, winders, pattern repeat and waste so you order the right length the first time.

Still deciding on material, width or pattern? Our hub on stair runners compares weaves, widths, backings and fitting styles side by side, then hands the numbers straight to the calculator.