Stair regulations UK: the building regs numbers for staircases
The building regulations numbers for a staircase in a house: rise, going, pitch, headroom, width, handrails and balustrades, loft conversion stairs, and what changes in Scotland, Wales and Northern Ireland.
A staircase in an English house can rise no more than 220 mm a step, can be no steeper than 42° and needs 2 m of headroom, with a handrail 900 to 1,000 mm above the steps. Those limits come from Approved Document K, the guidance on Part K of the building regulations. We set out each measurement, the loft conversion exceptions and what changes in Scotland, Wales and Northern Ireland.
The main stair measurements in England
These are the limits for a private stair, meaning one that serves a single home.
| Measurement | Limit | What it means |
|---|---|---|
| Rise (height of each step) | 150–220 mm | Every step in the flight has the same rise |
| Going (depth of each tread) | 220–300 mm | Measured nosing to nosing, less any overlap |
| Pitch | 42° maximum | Rules out a 220 mm rise on a 220 mm going |
| Twice the rise plus the going | 550–700 mm | Keeps each step in proportion to a stride |
| Headroom | 2 m | Clear height above the pitch line over the whole flight |
| Loft conversion headroom | 1.9 m centre, 1.8 m side | Only where 2 m cannot be reached |
| Handrail height | 900–1000 mm | Measured up from the pitch line or floor |
| Guarding | 900 mm minimum | On open sides where the drop is over 600 mm |
| Gaps in guarding | Under 100 mm | A 100 mm sphere must not pass through |
Approved Document K is guidance, not law. The legal requirement is a stair that is safe to use. Following the guidance is presumed to meet it, and a design that departs from it has to show building control that it still does. In a house the rules apply wherever the difference in level is more than 600 mm.
Rise, going and pitch
The rise is the height of one step, including the thickness of the tread. The going is the depth of the tread less any overlap with the tread above. In England a private stair can use any rise from 150 to 220 mm with any going from 220 to 300 mm, and every step in the flight has the same rise and the same going.
Two further checks apply to every stair. The pitch, the angle of the line joining the nosings, cannot exceed 42°, so a 220 mm rise needs a going of at least 245 mm. And twice the rise plus the going has to land between 550 and 700 mm.
A 2,600 mm floor-to-floor rise can be divided three ways, all within the English limits:
| Number of rises | Each rise | Going | 2R + G | Pitch | Flight length on plan |
|---|---|---|---|---|---|
| 12 | 216.7 mm | 245 mm | 678 mm | 41.5° | 2,695 mm |
| 13 | 200 mm | 250 mm | 650 mm | 38.7° | 3,000 mm |
| 14 | 185.7 mm | 220 mm | 591 mm | 40.2° | 2,860 mm |
All three pass in England. The 14-rise version fails in Scotland, where the going must be at least 225 mm. Fewer, taller steps do not buy much space either: the 12-rise stair needs a deeper going to stay under 42°, so its flight is only 165 mm shorter than the 14-rise one.
Headroom over the stairs
A stair needs 2 m of clear headroom along the whole flight and over its landings, measured straight up from the pitch line.
In a loft conversion where 2 m will not fit, the headroom can drop to 1.9 m at the centre of the stair, reducing to 1.8 m at the side. That relaxation applies to loft conversions only, including a velux loft conversion where the stair climbs under the existing roof slope. A stair in a new extension still needs the full 2 m.
Staircase width
Width is the rule that differs most between the four nations. In England, 800 mm is generally accepted for a main stair and 600 mm for a loft stair. Where the space allows, we would plan for 850 to 950 mm on a main stair and 700 to 750 mm on a loft stair.
Wales gives no minimum width for a stair in a house. Scotland and Northern Ireland both set one, at 900 mm and 800 mm for a main stair, and both allow 600 mm where the stair serves only one room.
Handrail height and when you need one
A handrail sits 900 to 1,000 mm above the pitch line on the flight, measured to the top of the rail. A stair under 1 m wide needs a handrail on at least one side, and a stair 1 m wide or more needs one on both sides.
In a house the two bottom steps can go without a handrail. The handrail can also form the top of the balustrade where the two heights line up. A flight between two walls still needs its handrail; what it can do without is a balustrade.
Balustrades, spindles and the 100 mm rule
Any open side of a flight or landing needs guarding where the drop is more than 600 mm. In most homes that is a balustrade, with the handrail on top and spindles or panels below, at least 900 mm high.
No gap in it may let a 100 mm sphere through, which means spindles set 99 mm apart or less. It also has to be hard for a child to climb, so horizontal rails are the design to avoid.
Open-riser stairs are allowed in a house as long as each tread overlaps the next by at least 16 mm and a 100 mm sphere cannot pass through the gap between treads.
Winders, landings and doors
Tapered treads, including kite winders on a turning stair, follow the same rise and going limits. The going is measured at the centre of the tread on a stair under 1 m wide, and 270 mm in from each side on a wider one. Every tapered tread needs at least 50 mm of going at its narrow end, and winders in a row share one going, no shallower than the straight treads in the flight.
Every flight needs a landing at the top and bottom, at least as wide and as long as the narrowest part of the flight, and clear of obstructions. Part of a floor can count as the landing. A door may swing across the landing at the foot of a flight only if it leaves 400 mm clear across the full width of the flight.
Spiral and helical stairs are designed to their own British Standard, BS 5395-2.
Loft conversion stairs
A loft conversion normally needs a full stair that meets the figures above, with the headroom relaxation where the roof is low. Building control checks the stair under Part K, alongside the structure, fire safety and insulation, whether or not the conversion needed planning permission.
Where a full stair cannot fit, two space-saving options are allowed, and only in a loft conversion:
- Alternating tread stair: paddle-shaped treads that alternate from side to side, in one or more straight flights. It needs handrails on both sides, slip-resistant treads, and a rise of no more than 220 mm with a going of at least 220 mm over the wide part of each tread.
- Fixed ladder: allowed only where a stair cannot fit without altering the existing space, with fixed handrails on both sides. A retractable ladder is not acceptable as a means of escape.
Both serve one habitable room only. An alternating tread stair can also reach a bathroom or WC, as long as that is not the only WC in the house. So the answer is no for a second bedroom in the loft: two habitable rooms need a full stair, even if it takes floor space from the storey below.
The loft stair is also the escape route from the new floor, so it needs to be fire-resistant for at least 30 minutes. It is priced as its own line, usually outside the headline loft conversion quote, and where it lands sets the price.
Stair regulations in Scotland, Wales and Northern Ireland
The figures above are England's. Wales, Scotland and Northern Ireland each publish their own stair guidance. The 42° pitch, the 550 to 700 mm range for twice the rise plus the going, and the 100 mm sphere rule for open risers hold in all four. The differences are in the rise, the going, the width and the handrails.
| Rule | England | Wales | Scotland | Northern Ireland |
|---|---|---|---|---|
| Rise | 150–220 mm | 220 mm maximum | 100–220 mm | 75–220 mm |
| Going | 220–300 mm | 220 mm minimum | 225 mm minimum | 220 mm minimum |
| Maximum pitch | 42° | 42° | 42° | 42° |
| Headroom | 2 m | 2 m | 2 m | 2 m |
| Loft headroom | 1.9 m centre, 1.8 m side | 1.9 m centre, 1.8 m side | A reduction may be considered | 1.9 m centre, 1.8 m side |
| Minimum width, main stair | 800 mm accepted in practice | None given | 900 mm | 800 mm |
| Handrail height | 900–1000 mm | 900–1000 mm | 840–1000 mm | 900–1000 mm |
| Open riser overlap | 16 mm | 16 mm | 15 mm | 16 mm |
Wales
Wales works from its own Approved Document K for use in Wales, the 1998 edition incorporating 2000 and 2010 amendments. Its maximum rise, minimum going, pitch and loft headroom match England's, and it sets no minimum stair width. In conversion work where space is short, it allows a spiral stair with tighter goings than BS 5395-2 if the stair serves no more than one habitable room.
Scotland
Scotland's rules sit in section 4.3 of the domestic Technical Handbook, and the work needs a building warrant rather than building regulations approval. A private stair can rise 100 to 220 mm a step with a going of at least 225 mm, and a flight generally has between 3 and 16 rises.
A stair between storeys is at least 900 mm wide, reduced to 800 mm where there is a continuous handrail on both sides and to 600 mm where it serves only one room or a bathroom. A private stair needs a handrail on one side once the change of level is more than 600 mm, set 840 to 1,000 mm high. Open risers are allowed with a 15 mm tread overlap.
Northern Ireland
Northern Ireland has its own building regulations and sets its stair rules in Technical Booklet H, dated October 2012. A private stair has a maximum rise of 220 mm, a minimum going of 220 mm and a 42° pitch, with 2 to 16 rises in a flight.
The minimum width is 800 mm, or 600 mm for a stair to one room that is not a kitchen or living room, and 900 mm where the stair is part of the circulation route on the entrance storey. Handrails are needed once a flight rises more than 600 mm, on both sides where the stair is 1,000 mm wide or more or is part of that entrance storey route.
Checking a staircase design before it is made
Ask the stair maker for a drawing that states the total rise, the number of rises, the rise, the going and the pitch, then check it before you pay a deposit.
Common questions
Is it a legal requirement to have a handrail on stairs in the UK?
Yes, a stair in a house needs a handrail once it rises more than 600 mm, which covers every stair between floors. A stair under 1 m wide needs one on at least one side and a wider stair on both sides, though the two bottom steps can go without. In Scotland a private stair needs a handrail on one side only.
Are stairs without banisters illegal?
A stair needs banisters, or another form of guarding, on any open side where the drop is more than 600 mm. A flight enclosed by walls on both sides needs no balustrade, but it still needs a handrail. Where guarding is fitted, it is at least 900 mm high and no gap may let a 100 mm sphere through.
What are the building regulations for loft conversion stairs?
A loft stair meets the same rise, going and 42° pitch limits as any other stair, with headroom relaxed to 1.9 m at the centre and 1.8 m at the side where 2 m will not fit. An alternating tread stair or a fixed ladder is allowed only where a full stair cannot fit, and only to one habitable room. The stair also needs at least 30 minutes of fire resistance.
What is the minimum width of a staircase in the UK?
A main stair in a house is at least 900 mm wide in Scotland and 800 mm in Northern Ireland, and both allow 600 mm for a stair to a single room. Wales sets no minimum. In England, 800 mm is generally accepted for a main stair and 600 mm for a loft stair.
What height should a stair handrail be?
A stair handrail sits 900 to 1,000 mm above the pitch line in England, Wales and Northern Ireland, measured to the top of the rail. Scotland allows 840 to 1,000 mm. The handrail can double as the top of the balustrade where the two heights match.
Do outdoor steps have to meet stair regulations?
Entrance steps that form part of the building fall under the stair rules, but steps on land leading up to a building, such as garden steps, do not. In Northern Ireland, guarding on an external flight at a house is at least 900 mm high.
Do spiral staircases have to meet building regulations?
Yes, a spiral or helical stair in a house is designed to BS 5395-2, the British Standard code of practice for spiral and helical stairs. In Wales, tighter goings can be accepted in conversion work where the stair serves one habitable room.