The staircase building regulations UK designers actually work to sit in Approved Document K, the 2013 edition, which covers protection from falling, collision and impact. For a stair inside a house it fixes three numbers above all others: a 220mm maximum rise, a 42 degree maximum pitch and 2m of headroom. What it does not fix, and this surprises almost everyone, is how wide the stair has to be.
Everything below is taken from Approved Document K itself, with the paragraph and table numbers, so you can check any of it against the source. It applies in England. Wales, Scotland and Northern Ireland run their own versions with different figures.
Rise and going: the table everything starts from
Table 1.1 of Approved Document K sets the permitted rise and going for three categories of stair. A stair inside a single dwelling is a private stair:
- Rise: minimum 150mm, maximum 220mm
- Going: minimum 220mm, maximum 300mm
- Maximum pitch: 42 degrees (note 1 to Table 1.1)
- Comfort rule: twice the rise plus the going should come to between 550mm and 700mm
The document is explicit that you may use any rise between the minimum and maximum with any going between the minimum and maximum, provided the relevant note is satisfied. That note is the pitch limit, and it is where most non-compliant stairs come from.
The trap: the maximum rise and the minimum going do not go together
A 220mm rise on a 220mm going gives a pitch of 45 degrees, because the rise and the going are equal. That breaks the 42 degree limit. It is the single most common mistake on a tight London stair, and it is easy to make because both numbers are individually allowed.
At the 42 degree limit the going has to be at least as long as the rise divided by the tangent of 42 degrees, which is roughly 1.11 times the rise. A 220mm rise therefore needs a going of about 245mm or more. A 200mm rise needs about 222mm. The practical window for a steep domestic stair is a rise around 200mm with a going around 225mm, which also satisfies the 2R plus G comfort rule at 625mm.
Headroom: 2m, and the loft conversion relaxation
Paragraph 1.11 requires a minimum of 2m of headroom on the access between levels, measured from the pitch line and over landings. That is the figure that kills most speculative loft stair layouts, because the head of the stair usually lands where the roof slope is coming down.
Paragraph 1.13 and Diagram 1.4 give the one relaxation, and it is specific to loft conversions in dwellings. Where there is not enough space to achieve 2m, the document accepts 1.9m over the half width of the stair, falling to 1.8m at the side. That is a concession for a genuine constraint, not a design target, and your building control body will expect to see why the full 2m cannot be achieved.
Width: there is no minimum for a house stair
This is the part that catches out people who have read a stair supplier's website rather than the document. Approved Document K sets minimum flight widths for buildings other than dwellings: 1200mm between enclosing walls and 1000mm between handrails. For dwellings it sets no general minimum width at all.
The only width figure for a dwelling is in paragraph 1.16, and it is narrow in scope: where a severely sloping plot forces a stepped change of level within the entrance storey, that stair must be at least 900mm wide. Everywhere else in a house, width is a design decision rather than a regulation. Around 800mm to 900mm feels normal, 750mm reads as tight, and anything under about 700mm makes moving furniture a serious problem. None of that is in Part K, which is exactly why it is worth saying.
Flights, landings and doors
- Long runs. If a stair has more than 36 risers in consecutive flights, there must be at least one change of direction between flights (paragraph 1.17).
- Doors onto landings. In a dwelling a door may swing across a landing at the bottom of a flight, but only where at least 400mm of clear landing remains across the full width of the flight (paragraph 1.24 and Diagram 1.8). In buildings other than dwellings you need an unobstructed 1200mm on each landing.
- Under the stair. Where the soffit beneath a stair is less than 2m above floor level, the area beneath has to be protected with guarding and low level cane detection, or a barrier giving the same protection (paragraph 1.8).
Open risers, handrails and guarding
These three are where a beautiful stair design meets its constraints, and they are worth knowing before a joiner quotes.
Open risers
Open risers are permitted in dwellings, subject to two conditions in paragraph 1.9: treads must overlap by at least 16mm, and the steps must be built so that a 100mm diameter sphere cannot pass through the opening. That second rule is the child-safety test and it is the one that decides how far apart the treads can sit. In the common access areas of a block of flats, open risers are not allowed at all.
Handrails
The top of the handrail sits 900mm to 1000mm above the pitch line or the floor. If the stair is 1000mm or wider, you need a handrail on both sides. The handrail may form the top of the guarding where the heights match, which is how most slim contemporary balustrades are detailed.
Guarding heights
For a single family dwelling, guarding to stairs, landings, ramps and the edges of internal floors is 900mm. External balconies, including Juliette balconies, and the edges of roofs are 1100mm. In blocks of flats it is 900mm to stairs and ramps and 1100mm to landings and floor edges. In every case the 100mm sphere rule applies, so that a child cannot be held fast by the guarding.
Spiral stairs, alternating treads and ladders
Where a conventional stair will not fit, Part K allows three alternatives, and it is strict about when.
- Spiral and helical stairs should be designed to BS 5395-2 (paragraph 1.28). They are not a loophole around the rise and going table; they are a different standard.
- Alternating tread stairs may be used only in a loft conversion, only where there is not enough space for a stair meeting paragraphs 1.2 to 1.24, and only for access to a single habitable room plus, if wanted, a bathroom or WC, provided that is not the only WC in the dwelling. Construction has to follow Diagram 1.10: minimum going 220mm, maximum rise 220mm, uniform steps with parallel nosings, slip-resistant treads, handrails on both sides and a full 2m of clear headroom.
- Fixed ladders are allowed only for access in a loft conversion containing one habitable room, only where a compliant stair cannot be fitted without altering the existing space, and they must have fixed handrails on both sides. Retractable ladders are not acceptable as a means of escape.
Note what all three have in common: they are for a loft with one room, they require the conventional stair to be impossible rather than inconvenient, and building control has to agree that. If you are planning a loft with two bedrooms, you are building a full stair.
When a staircase needs building control
A new staircase, a replacement staircase, or any alteration that changes the rise, going, pitch or structure is building work and needs building control approval, either through a local authority application or an approved inspector. Replacing a handrail or balustrade to the same geometry generally does not. A loft conversion always does, and the stair is usually the hardest single element in the application.
Two London-specific layers sit on top. In a listed building, altering or replacing a historic staircase needs listed building consent regardless of what Part K says, and the consent may take priority over the modern dimensions. In a leasehold flat, moving or forming a stair almost always needs a licence to alter from the freeholder before any of this matters. Our guide to building regulations for a London renovation covers how the approvals fit together.
Designing a stair people actually like using
Compliance is the floor, not the brief. Three things separate a stair that meets Part K from one that feels right:
- Consistency. Every rise in a flight should be identical. A single riser out by 10mm at the top of a flight is what people trip on, and it is the most common defect in a converted period house where levels have moved.
- Landing generosity. The 400mm door clearance is a minimum. A half landing you can stand on with a laundry basket changes how the house works.
- Light. A stair with no natural light reads as narrower than it is. In a Victorian terrace with a dogleg stair, a rooflight over the well does more for the feel of the space than 100mm of extra width.
If you are working through a loft, our guide to designing a loft conversion covers where the stair usually has to land, and designing in a period property covers the detailing that keeps a new stair in keeping with an old house.
Frequently asked questions
What is the maximum rise and minimum going for stairs in the UK?
For a private stair inside a dwelling in England, Approved Document K Table 1.1 sets a rise of 150mm to 220mm and a going of 220mm to 300mm, with a maximum pitch of 42 degrees. You can pair any rise in that range with any going in that range as long as the pitch stays within 42 degrees, which means the maximum rise and the minimum going cannot be used together.
Can a staircase be 45 degrees?
Not in a dwelling. The maximum pitch for a private stair is 42 degrees under note 1 to Table 1.1 of Approved Document K. A 220mm rise with a 220mm going produces exactly 45 degrees, which is why that combination fails even though both figures are individually within the table. To hold 42 degrees, the going needs to be roughly 1.11 times the rise or more.
What is the minimum headroom above a staircase?
Two metres on the access between levels, under paragraph 1.11. There is one relaxation, for loft conversions in dwellings: where 2m cannot be achieved, paragraph 1.13 and Diagram 1.4 accept 1.9m over the half width of the stair, falling to 1.8m at the side. You need to show building control why the full 2m is not achievable.
Is there a minimum staircase width in a house?
No. Approved Document K sets minimum flight widths for buildings other than dwellings, 1200mm between walls and 1000mm between handrails, but no general minimum for a stair inside a dwelling. The only figure is paragraph 1.16, which requires 900mm for a stepped change of level within the entrance storey where a severely sloping plot makes one unavoidable. In practice 800mm to 900mm is the comfortable range.
Are open riser stairs allowed under building regulations?
Yes, in dwellings, subject to paragraph 1.9. The treads must overlap by at least 16mm and the steps must be built so a 100mm diameter sphere cannot pass through the gap between them. The sphere rule is what governs how open the stair can look. In common access areas in blocks of flats, risers must not be open.
How high should a staircase handrail and balustrade be?
The top of the handrail goes 900mm to 1000mm above the pitch line or floor, and a stair 1000mm or wider needs a handrail on both sides. For guarding in a single family dwelling, 900mm applies to stairs, landings, ramps and internal floor edges, rising to 1100mm for external balconies, Juliette balconies and roof edges. A 100mm sphere must not be able to pass through any guarding.
Sources
- Approved Document K, protection from falling, collision and impact, 2013 edition: Table 1.1 and note 1, paragraphs 1.8, 1.9, 1.11, 1.13, 1.15, 1.16, 1.17, 1.24, 1.28 to 1.32, 1.34, Diagrams 1.4, 1.8 and 1.10, and Table 3.1 guarding heights: gov.uk
- Vertigo Interiors, related guidance: minimum bathroom size in the UK and the Vertigo Interiors homepage
Checked on 27 August 2026 against Approved Document K, 2013 edition, published 3 January 2013. Part K applies in England; Wales, Scotland and Northern Ireland use different documents and some different figures. Confirm the standards your project is subject to with your building control body before you order a staircase.