If the stair is fixed to the house, plan on needing it. A stair that forms part of the building, like a steel stair bolted to the back wall up to a first-floor door, is covered by Part K of the Building Regulations, and if putting it in counts as building work you need approval before you start. Steps built on the ground leading up to a house are treated differently: the Planning Portal says external steps won't normally need approval unless they are part of the access to the building.
We make outside stairs in our Bromley workshop and set each one out against the regulations before cutting steel. It isn't always obvious whether your job has to go through building control. The council's building control, or a registered approver, makes the call.
- Steepest pitch42°the most a private stair, one serving a single home, can climb at
- Headroom2 mclear height wanted over the flights and the landings
- Gaps in the guarding100 mma ball this size must not pass through where under-fives may use the stair
When an outside stair counts as building work
Regulation 3 of the Building Regulations 2010 sets out what building work is. The list takes in putting up or extending a building, and a "material alteration", which is work that leaves a building falling short of certain requirements where it met them before, or, where it already fell short, leaves it more unsatisfactory. Those requirements include Part A (structure) and B1 (means of warning and escape).
A steel stair hangs a lot of weight off a wall, and it often needs a new doorway as well. Assume building control will want to see it and ring them early.
Approved Document K says its stair guidance covers internal and external steps and stairs when they are part of the building. It gives a plain example: requirement K1 doesn't apply to steps on land leading to a building, but it does apply to entrance steps that are part of it.
Gov.uk lists most repairs, replacements and maintenance as exempt. Swapping a rotten timber stair for steel? Ask building control. Don't guess.
What Part K asks of the stair itself
Approved Document K calls a stair meant for one home only a private stair. For a private stair, outside or in, the main points are:
| Item | What Part K asks |
|---|---|
| Rise and going | Each step rises 150 to 220 mm, with a going of 220 to 300 mm. Twice the rise plus the going should come to between 550 and 700 mm, and every step in a flight should be the same, with level treads. |
| Pitch | No steeper than 42°. |
| Headroom | At least 2 m over the flights and landings. |
| Handrails | The top of the rail sits 900 to 1000 mm above the pitch line, and a stair that's 1000 mm wide or wider needs a rail on both sides. |
| Guarding | In a home, the sides of flights and landings need guarding once the drop goes beyond 600 mm. For a single-family house, Diagram 3.1 sets 900 mm on stairs and landings, and 1100 mm on external balconies and the edges of roofs. |
| Small children | Where under-fives may use the building, a 100 mm sphere mustn't pass through any gap in the guarding, and it shouldn't be easy to climb. Open risers in a home need treads overlapping by at least 16 mm, and the opening between treads must stop a 100 mm sphere too. |
| Landings | Each flight gets a landing top and bottom, no narrower and no shorter than the narrowest part of the flight. |
| Spiral and tapered stairs | Spirals are designed to BS 5395-2. Tapered external steps on a home need a going of at least 280 mm. |
A stair serving more than one flat isn't a private stair, so stricter figures can apply. A general access stair has a 170 mm maximum rise and a 250 mm minimum going. In the common parts of a building with flats, the guidance asks for closed risers and nosings picked out in a contrasting material. Where there's no passenger lift, it wants continuous handrails on both sides. Diagram 3.1's residential category gives 900 mm guarding on the flights and 1100 mm everywhere else. Landlords splitting a house into flats should check this with building control first.
Our external staircases show these figures on the drawing before anything is made.
When the stair is also a fire escape
Approved Document B Volume 1 (Dwellings) also applies if the stair is part of a way out in a fire. In a house with a storey more than 4.5 m above ground, one option it gives is an alternative escape route from the top storey to its own final exit. Where an outside stair forms part of an escape route from a house, paragraph 2.17 asks for:
- fire resisting doors onto the stair (minimum E 30), except a single exit door from the building to the top landing of a stair that leads down
- fire resisting construction in the outside of the building (minimum RE 30) within 1800 mm to the side of the flights and landings, 9 m below them and 1100 mm above the top landing
- any glazing in those zones fixed shut and fire resisting (minimum E 30)
- weather protection on stairs over 6 m high, to stop snow and ice building up, though full enclosure isn't needed
For flats, the same volume lets a single access stair be external if the floor it serves is no more than 6 m above ground, with similar conditions and self-closing fire doors. More on our fire escape staircases.
Where steps form part of the way into a house, Approved Document K also points to Approved Document M, and the Planning Portal warns that the work mustn't make the house harder to get into.
Got a stair in mind?
Send a photo of the wall and roughly how high the door is, and we'll draw it to the regulations.
How you get approval
- Pick a building control body. That's your local council's building control or a registered building control approver; an approver will tell the council about the work.
- Full plans or a building notice. Gov.uk calls full plans the most thorough route, with a decision within 5 weeks, or 2 months if you agree. A building notice is only for smaller projects, and work can start 2 days after it goes in.
- Competent person schemes. Installers registered with one can self-certify certain work; gov.uk's examples are windows and boilers. Ask whoever fits your stair if any scheme covers it.
- Completion certificate. You'll usually get it within 8 weeks of the work finishing, as long as it complies. Keep it with the house deeds.
Skipping approval isn't a saving. Gov.uk warns that the person doing the work could be prosecuted and fined, the building control body could make you pay to put faulty work right, and you won't have the certificates you may need when you sell. Work done without consent after 11 November 1985 can be put to the council for regularisation, but you might need to make alterations first.
Planning permission is a different thing altogether; our page on balcony planning permission in Bromley covers the platforms that often sit at the top of these stairs.
Where these facts come from
- The Building Regulations 2010, regulation 3: meaning of building work (legislation.gov.uk)
- Approved Document K, covering protection from falling, collision and impact (gov.uk), Table 1.1, paragraphs 0.3, 1.1 to 1.41 and Diagram 3.1
- Approved Document B: fire safety, Volume 1: Dwellings (gov.uk), paragraphs 2.5, 2.17 and 3.68 to 3.71
- Building regulations approval (gov.uk), including how to apply and when you don't need approval
- Do new external steps outside my house need planning permission or building control approval? (Planning Portal)
Checked: 10 October 2026. The guidance changes from time to time, so check the current versions, and your own building control body, before you rely on a figure.
Planning an outside stair? Ring 07828 730 888, or use the quote form at the foot of this page. The survey is free, and the drawing you get afterwards shows the stair's sizes, ready to go with your building control application. Or book your survey from the contact page.
Quick questions
Do garden steps need building regulations approval?
Not normally. Approved Document K says requirement K1 doesn't cover steps on land leading to a building, and the Planning Portal says external steps won't normally need approval unless they are part of the access to the building.
How steep can an outside stair to a flat or house be?
For a private stair, one serving a single home, Approved Document K allows a pitch of up to 42°, with each rise between 150 and 220 mm and each going between 220 and 300 mm.
How high does the railing on an external stair need to be?
On a single-family house, Diagram 3.1 of Approved Document K sets 900 mm for guarding on stairs and landings, and 1100 mm on external balconies. Where under-fives may use the stair, no gap should let a 100 mm sphere through.
Can I get approval after the stair is already up?
Possibly. Your local council can consider a regularisation application for work done without consent after 11 November 1985, though you might need to make alterations before it will issue a certificate.
Does an external stair also need planning permission?
That's a separate question from building regulations. The Planning Portal says garden steps don't normally need planning permission, but steps that are part of a bigger project, such as a raised deck, may, and different rules may apply to listed homes and conservation areas.