Lofts
Loft conversion stairs in London: the Part K rules, and the review now under way
Finding room for a staircase is often the hardest part of a loft conversion. On 19 October the Building Safety Regulator opened a call for evidence on Part K, the building regulation that covers stairs. The current rules stay in force while it runs, so here is what they require now.
Most London loft conversions succeed or fail on the staircase. The new flight has to land somewhere sensible on the floor below, give enough headroom under a sloping roof and form part of a safe escape route in a fire. The rules sit in Part K of the Building Regulations 2010 and its statutory guidance, Approved Document K, together with the fire safety guidance in Approved Document B. This article is general information, not legal or design advice.
What the Building Safety Regulator announced
On 19 October 2026 the Building Safety Regulator (BSR) launched a call for evidence on Part K and Approved Document K, which cover protection from falling, collision and impact: stairs and ladders, ramps, handrails, guarding, windows, doors, glazing and vehicle barriers. The regulator says it has been more than 20 years since a substantial review of Part K took place.
Three points matter for homeowners planning a loft now:
- The call for evidence is not proposing policy changes. The BSR says it is gathering evidence to set priorities for future work.
- The current requirements and guidance remain in place while the review is under way, so schemes being designed today should follow the existing Approved Document K.
- Any future change to the regulations or guidance would be subject to further consultation.
The call for evidence opened on 19 October and closes on 28 December 2026. Responses are welcome from building control bodies, designers, builders and manufacturers, and the BSR also wants to hear from people who live in and use buildings. Alongside it, the government published research on domestic stair design, and the Health and Safety Executive published research report RR1228 on fixed ladders, alternating tread stairs and steep stairs: the special stair types currently allowed in loft conversions where there is not room for a standard stair. The HSE report cites a Royal Society for the Prevention of Accidents estimate that more than 700 people die and more than 43,000 are hospitalised in England each year after a fall on stairs at home.
The current rules for a standard loft stair
A stair inside a house is a "private stair" in Approved Document K (2013 edition). Table 1.1 sets the step dimensions:
- each rise between 150mm and 220mm;
- each going (tread depth, less any overlap) between 220mm and 300mm;
- a maximum pitch of 42 degrees; and
- twice the rise plus the going between 550mm and 700mm.
Open risers are allowed in a house if the treads overlap by at least 16mm and a 100mm sphere cannot pass through the gaps. Landings, at least as wide and long as the narrowest part of the flight, are needed at the top and bottom of every flight. Handrails should be 900mm to 1000mm above the pitch line, and on both sides if the stair is 1000mm or wider. Guarding is needed where there is a drop of more than 600mm. Approved Document K gives no general minimum width for a stair inside a house, but the stair must still work as an escape route, so agree the design with building control early.
Headroom under a sloping roof
The normal minimum clear headroom over a stair and its landings is 2 metres. For loft conversions in houses, where there is not enough space to achieve this, Approved Document K accepts reduced headroom of 1.9m at the centre line of the stair, reducing to 1.8m at the side. This concession is often what allows a new flight to rise beneath a roof slope or under an existing ridge.
Existing houses
The guidance on Table 1.1 says its dimensions should be followed in existing buildings unless dimensional constraints make that impossible. Any alternative should be agreed with the building control body. This is relevant in narrow London terraces, where the new stair usually has to fit over the existing one.
When space-saver stairs and fixed ladders are allowed
Approved Document K allows two special options only in loft conversions, and only where there is not enough space for a conventional stair:
- An alternating tread stair (often sold as a "space saver") in one or more straight flights, serving only one habitable room plus, if wanted, a bathroom or WC that is not the only WC in the house. Steps must be uniform with parallel nosings and slip-resistant treads. Diagram 1.10 shows a maximum rise of 220mm, a minimum going of 220mm and handrails on both sides. Unlike a standard loft stair, it needs the full 2m clear headroom.
- A fixed ladder with fixed handrails on both sides, only for a loft conversion containing one habitable room. Retractable ladders must not be used as a means of escape.
These stair types are the subject of the HSE research published alongside the call for evidence, so they are one area to watch if the guidance is revised. For now, a loft with two bedrooms, or a bedroom and a study, needs a stair that meets the full private stair rules.
Fire escape: the stair is part of the escape route
Adding a habitable loft to a two-storey house usually creates a storey more than 4.5 metres above ground level. Paragraph 2.21 of Approved Document B, Volume 1 then says the full extent of the escape route should be addressed, with fire-resisting doors (minimum E 20) and partitions (minimum REI 30), including upgrading existing doors where necessary. Open-plan ground floors need new partitions to enclose the route. As an alternative, paragraph 2.23 describes sprinkler protection to open-plan areas, combined with a fire-resisting partition and door separating the ground storey from the upper storeys and access from the loft to a first-floor escape window. Where existing doors have historic or architectural merit, the guidance says retaining and, where necessary, upgrading them should be investigated. Our loft conversion regulations guide covers fire safety alongside structure and insulation.
Planning, party walls and sign-off
A stair is internal work and does not need planning permission in itself, but the dormer or roof extension that creates the headroom might. See our guide to dormer, hip-to-gable and mansard conversions. Steel beams for a new floor or dormer are often supported on the party wall in terraced and semi-detached houses, so read our Party Wall Act guide before work starts. Every habitable loft conversion needs building regulations approval. Our guides to building control charges and completion certificates explain the process and why the certificate matters when you sell.
A short checklist
- Before the roof design is fixed, have your designer show where the new stair will land and confirm it achieves the private stair dimensions and the 1.9m/1.8m headroom.
- Rely on a space-saver stair or fixed ladder only if a conventional stair genuinely cannot fit and the loft will contain only one habitable room.
- Plan the protected escape route, including any fire door upgrades on the floors below, as part of the same drawings.
- Agree any departure from Table 1.1 with building control in writing before work starts.
- If you have experience of steep or space-saving stairs, consider responding to the BSR call for evidence by 28 December 2026.
For indicative 2026 London build-cost ranges, including loft conversions, see our cost guide. Whether you are converting a terrace loft in Lambeth or a semi in Barnet or Croydon, you can request quotes from independent local builders when you are ready. Home Builders does not carry out building work: we ask advertisers to provide proof of insurance, and any contract is between you and the builder you choose.
Sources: Building Safety Regulator: Have your say on the future of Part K of the building regulations (19 October 2026); BSR: Call for evidence for the review of Part K; Approved Document K: Protection from falling, collision and impact, 2013 edition (paragraphs 1.2 to 1.41, Table 1.1, Diagrams 1.4 and 1.10); Approved Document B: Fire safety, Volume 1: Dwellings (paragraphs 2.21 to 2.23); GOV.UK: Evidence to support potential changes to Approved Document K guidance on domestic stairs; GOV.UK: Approved Document K, general access and utility stairs; HSE RR1228: Safety of stairs for limited access in dwellings. This article is a summary, not legal advice; confirm the requirements for your project with your building control body.
Frequently asked questions
What is the minimum headroom for loft conversion stairs?
Normally 2 metres. Where there is not enough space in a loft conversion, Approved Document K accepts 1.9m at the centre line of the stair, reducing to 1.8m at the side. Alternating tread stairs need the full 2m.
Can I use a space-saver stair for my loft conversion?
Only if there is not enough room for a conventional stair, and only if the loft contains one habitable room, plus optionally a bathroom or WC that is not the only WC in the house. The stair must be in straight flights with handrails on both sides.
Is a pull-down loft ladder allowed for a loft bedroom?
No. Approved Document K says retractable ladders must not be used as a means of escape. A fixed ladder with handrails on both sides is allowed only for a loft conversion with one habitable room where no other stair can fit.
Are the stair rules changing?
Not yet. The Building Safety Regulator's call for evidence on Part K runs until 28 December 2026 and does not propose changes. The current guidance stays in force, and any future changes would be consulted on.
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