UK Staircase Building Regulations, Explained

Four nations, four rulebooks

There is no single UK staircase regulation.

• England: Approved Document K (2013 edition).
• Wales: its own Approved Document K, reissued 2017 but still based on the older 1998 edition, and unlike England it still cross-references Approved Document N for glazing. The private-stair numbers are effectively the same as England.
• Scotland: no Part K at all. Stairs sit in the Building Standards Technical Handbook (Domestic), Section 4 (Safety), currently the April 2026 edition. Several numbers differ.
• Northern Ireland: Technical Booklet H (2012), with its own figures again.

If you take one thing from this page: Scotland and NI are not England. Scotland needs a 225mm going (not 220mm), guards the flight at 840mm (not 900mm), and caps a flight at 16 risers. NI allows a rise as low as 75mm and sets its own widths. Copying England's numbers onto a Scottish or NI job is how people get it wrong.

The core numbers (private stair in a home)

The 2R plus G rule. Twice the rise plus the going should land between 550mm and 700mm, on every stair, in all four nations. It is the comfort check. An easy, common stair is a 175mm rise with a 250mm going: 2 x 175 + 250 = 600mm.

The 45 degree trap. You cannot pair the maximum 220mm rise with the minimum 220mm going, because that is exactly 45 degrees and breaks the 42 degree limit. A compliant stair satisfies the rise, the going, the pitch and the formula all at once.

Headroom, and how to check it

You need 2 metres of clear headroom, measured straight up from the pitch line (the line joining the front edge of each nosing) over the whole flight and the landings.

To check it yourself, find the tightest point. It is almost always where the stair passes under the floor above or under the edge of the stairwell opening (the trimmer), not the open middle of the flight. Measure vertically from the nosing line to the underside of that ceiling or trimmer. That pinch point is what fails headroom.

Loft conversions get a small relaxation where the full 2 metres genuinely cannot be met: England and NI allow it to drop to 1.9m at the centre of the stair width, tapering to 1.8m at the side. Scotland's handbook does not publish an explicit reduced figure; it allows a reduction to be considered, so a Scottish loft needs the building standards verifier to agree it, not a number off a website.

Handrails

• Height: 900mm to 1000mm above the pitch line in England, Wales and NI; 840mm to 1000mm in Scotland.
• One side is the minimum; both sides if the flight is 1000mm wide or more.
• A handrail can double as the top of the guarding where the heights line up.
• Continuous is the quality standard. A good handrail runs continuously along the flight and around every turn and landing, unbroken, so your hand never leaves it. A cheap one stops and restarts at each newel. On common and non-dwelling stairs it must continue 300mm past the top and bottom nosings (Scotland disapplies that for a single dwelling). Continuous is safer, and it is one of the tells of a properly made stair.

Guarding and the 100mm sphere

• A 100mm sphere must not pass through any gap in the guarding, so no gap wider than about 99mm. This applies in every home, children or not, and where under-fives may be present the guarding must also not be climbable (no horizontal ladder rails).
• Height in a home: 900mm on stairs, landings and internal floor edges in England, Wales and NI. Scotland is 840mm on the flight, 900mm on landings and within-dwelling floor edges (a mezzanine edge), and 1100mm only for non-dwelling and external locations.
• External balconies and roof edges: 1100mm everywhere.
• Guarding is required wherever there is a drop of more than 600mm in a home. The two or more risers trigger you see quoted is the non-dwelling rule, not the domestic one.

Open risers

Open-riser stairs are allowed in a home if the treads overlap by at least 16mm (15mm in Scotland) and a 100mm sphere cannot pass through the gap. If a source tells you the overlap is 60mm, they have misread the 60 degree tread-profile angle in the diagram. It is 16mm.

How many steps in a flight

• England and Wales set no limit on risers per flight for a home. The 16 risers figure all over the web is the rule for non-dwellings, not houses. For a home, once you go over 36 risers across consecutive flights you need a change of direction of at least 30 degrees.
• Scotland caps it: maximum 16, minimum 3 per flight.
• Northern Ireland caps it too: maximum 16, minimum 2.

There is also a real-world limit nobody prints: on a solid-timber straight flight the string is a single length of timber, and timber only grows so long, so past a certain length you physically cannot make it in one piece and the run has to break with a landing or a turn.

Width

England and Wales set no minimum width for a private home staircase (the only 900mm figure is a narrow steep-plot exception). Scotland does: 900mm generally, 600mm to a single room or sanitary space, or 800mm where handrails run both sides. NI sets 600mm, 800mm or 900mm depending on what the stair serves. So the claim that the minimum is 800mm is wrong for England and real for Scotland and NI.

Winders, landings, and when you have no choice

At a turn you either use winders (tapered treads that turn the corner) or a landing (a flat platform). It is often not a free choice:

• A landing is safer and more comfortable but eats floor space and, crucially, headroom. A landing tucked under a low ceiling can fail the 2-metre rule, which forces you back to winders.
• Winders save space and can hold headroom over the turn, but they are trickier underfoot.

Where winders are used, the going is measured at the centre of the tread on a stair under 1 metre wide (270mm in from each side on wider stairs), consecutive winders must share the same going, that going must be at least as large as the straight treads, and the narrow end of any winder must be at least 50mm.

Spiral and helical stairs

Spiral stairs (around a central column) and helical stairs (a true open helix, no column) are not designed to the rise-and-going table above. They follow BS 5395-2. A spiral or helical stair can serve a loft, but as a sole escape route it usually triggers extra fire provisions (a mains smoke alarm and an FD30 door at the bottom).

Space-saver (alternating-tread) stairs

Legal only as a last resort: a loft conversion, only where no compliant stair fits, serving one habitable room (plus optionally a bathroom or WC, but not the home's only WC), with handrails both sides. And the bit most summaries miss: under fire rules (Approved Document B) an alternating-tread stair cannot be your only means of escape.

Do you need Building Control sign-off?

• New, relocated or materially altered stairs: yes. So does forming a new floor opening.
• Genuine like-for-like repair (a broken tread, a repaint, tightening a spindle) is generally exempt, but confirm with the building control body first. Replacing spindles or a handrail in the same position is usually not notifiable.
• Stairs are not self-certifiable. Competent Person Schemes cover electrics, gas, windows and the like, not structural or stair work, so it must be notified.
• In England and Wales you use either Local Authority Building Control or a Registered Building Control Approver (RBCA). The old Approved Inspector role was abolished on 6 April 2024; individual inspectors are now Registered Building Inspectors. Choose Full Plans over a Building Notice for a stair or loft, and keep the completion certificate, because your buyer's solicitor will ask for it.
• In Scotland you must get a Building Warrant before work starts. It is an offence to begin without one, and only the local authority verifies (no private route).
• In Northern Ireland only the district council does building control (no private approvers).

The myths this page kills

1. 16 risers max in a house: false in England and Wales (no cap); true in Scotland (16 and 3) and NI (16 and 2).
2. Minimum stair width is 800mm: not in England or Wales; real in Scotland and NI.
3. England's rules apply in Scotland: no, it is a 225mm going, 840mm flight guarding, a 16-riser cap and set widths.
4. Minimum rise is 150mm: England yes, but NI is 75mm.
5. Guarding is always 1100mm: no, it is 900mm on home stairs and landings; 1100mm is for external and roof edges.
6. Ask for an Approved Inspector: abolished April 2024; it is now an RBCA and Registered Building Inspectors.
7. Part M forces shallow steps inside a house: no, the internal stair follows Part K; the accessibility rules add width for a stairlift, not shallower steps.
8. Wales is the same as England: the numbers match, but Wales runs its own older document with different glazing and accessibility rules.