2026-09-06 · HawkSwift Ltd

Second Staircase Rule 2026: Approved Document B Changes for Flats Over 18m

On 30 September 2026, the most significant update to fire-safety design guidance for flats in England in over a decade takes effect. Approved Document B (Fire Safety) — the statutory guidance that supports the Building Regulations — is being amended so that new blocks of flats with a top storey 18 metres or more above ground level should be served by more than one common staircase.

If you design, develop, manage or own residential buildings, this changes the default fire-safety standard for new-build flats, and it changes how escape routes, evacuation lifts and fire doors are judged. For owners and managers of *existing* blocks, there is no automatic requirement to bolt on a second staircase — but there is a real need to check that your fire risk assessment and evacuation strategy still stack up against the new guidance. Here is what changes, what stays the same, and what you should do about it.

What is Approved Document B and why is it changing?

Approved Document B (AD B) is the government's technical guidance on meeting the fire-safety requirements of the Building Regulations 2010 — most importantly requirement B1, which covers means of escape in case of fire. It is guidance, not legislation itself: follow it and your design is normally accepted as meeting the regulations; propose something different and you must justify it through an alternative fire-engineering approach.

The changes come from the post-Grenfell reform programme. In September 2024 the Ministry of Housing, Communities and Local Government (MHCLG) announced three amendment booklets to Approved Document B:

2 March 2025 — removal of the national BS 476 classification for reaction to fire and roofs, plus sprinklers in all new care homes regardless of height (Circular 03/2024).
30 September 2026 — second-staircase provisions for residential buildings over 18 metres, plus new escape and evacuation-lift guidance (Circular 04/2024).
2 September 2029 — removal of the remaining BS 476 references for fire resistance, moving fully to European standards (Circular 05/2024).

The official MHCLG circular letter sets out the full programme. Notably, Scotland has required two stairs in blocks above 18 metres for decades — the 2026 change brings England's guidance in line with that long-established approach.

The headline change: two common staircases above 18 metres

From 30 September 2026, Approved Document B Volume 1 (dwellings) recommends that flats should be served by more than one common stair where the building has a top storey 18 metres or more in height.

Key points to understand:

How the 18 metres is measured. The height is measured to the top storey using the method set out in Approved Document B — it is *not* simply the roof height, parapet height or the height quoted in planning documents. In practice 18 metres is roughly five to six storeys.
It is a recommendation in guidance. Because AD B is guidance, a designer could in principle propose a fire-engineered solution with a single stair. In practice, building control bodies and fire authorities will expect the new standard to be followed, and departures will need robust technical justification.
Interlocked stairs don't count as two. The amended guidance is explicit that interlocked stairs are treated as a single escape route and do not provide alternative means of escape. Two stairs that share common points of failure do not meet the intention of the change.
The escape strategy must be reviewed as a whole. Stair independence and separation, horizontal escape from flats, access to storey exits, travel distances, corridor and lobby arrangements, smoke control, firefighting access and structural fire resistance all have to be considered together. Adding a second staircase to an existing layout is rarely a bolt-on — it affects the core, floor area, structure, services and cost.

Design teams should also re-verify travel distances to storey exits under the restructured escape guidance, which now separates horizontal escape from vertical escape more clearly.

Evacuation shafts and evacuation lifts

The 2026 amendments introduce new provisions for evacuation lifts where they are provided — they do *not* create a general requirement for evacuation lifts in every block of flats.

Where an evacuation lift is provided, the guidance says it should sit within an evacuation shaft containing:

a protected stairway,
the evacuation lift, and
an evacuation lift lobby acting as a refuge area for people waiting for the lift.

The lobby must have direct access to the protected stairway and must not be directly accessible from a flat, maisonette, storage room or electrical equipment room.

This matters for personal emergency evacuation plans (PEEPs) and for residents who cannot use stairs independently. The government has separately consulted on wider evacuation-lift requirements for taller buildings, but those proposals are not yet settled requirements — do not confuse the consultation with the changes that take effect in September 2026.

Other changes in the 2026 booklet

Alongside the second-staircase recommendation, the 2026 amendments:

Restructure the escape guidance, separating horizontal escape from vertical escape and introducing new definitions including *evacuation shaft*, *evacuation lift lobby*, *interlocked stair* and *storey exit*.
Tighten provisions for refuse rooms and refuse chutes. Rooms containing refuse chutes or refuse storage must not be situated within a protected stairway, evacuation shaft or protected lobby — and access should be through a protected lobby with a minimum of 0.2m² of permanent ventilation.
Emphasise protected lobbies as the buffer between flat entrance doors and the common stairway, keeping the staircase smoke-free during a fire in any individual flat.

What has NOT changed: existing buildings

This is the point that causes the most confusion — and the answer matters to every block-of-flats landlord and manager in the UK:

The September 2026 changes do not automatically require a second staircase to be added to existing buildings over 18 metres.

The second-stair recommendation concerns the design of new blocks of flats. Existing buildings continue to be assessed against their actual construction, use, evacuation strategy and fire precautions. That said, existing buildings are far from untouched:

Your fire risk assessment under the Regulatory Reform (Fire Safety) Order 2005 must remain current and must reflect the real escape provision in the building. If the building relies on a single staircase with a stay-put strategy, that strategy needs to be documented, justified and workable.
Higher-risk buildings (18 metres or more, or 7 storeys or more) are within the Building Safety Act 2022 regime — the accountable person must maintain a safety case and keep residents informed. See our guide to fire risk assessment for flats and Building Safety Act duties.
If you extend, convert or materially alter an existing building, you must consider which parts of the Building Regulations apply to the work, whether it makes existing conditions no worse, and whether the evacuation strategy remains suitable. Building Regulation 38 also requires fire-safety information to be passed on at completion.
Fire doors, lobbies and escape routes must be maintained — monthly checks of fire doors in the common parts of multi-occupied residential buildings are already required under the Fire Safety (England) Regulations 2022.

If a block has an outdated or incomplete fire strategy, a retrospective fire strategy review or technical assessment is the right first step — before the FRA is relied upon.

Transitional arrangements: does your project qualify?

As with the 2025 changes, there is a transitional window. The previous (2019) edition of AD B incorporating the 2020 and 2022 amendments continues to apply where, before 30 September 2026:

a building notice or initial notice has been given to the relevant authority, or a building control approval application with full plans has been made, and
the building work has started and is sufficiently progressed by 30 September 2026, or starts and is sufficiently progressed within 18 months of that date (i.e. by around 30 March 2028).

For new construction, "sufficiently progressed" means the pouring of concrete for the permanent placement of trench, pad or raft foundations has started, or the permanent placement of piling has started. For work to an existing building, it means the work has started.

If your scheme is close to the deadline, confirm with your building control body which edition applies *before* relying on an existing design — getting this wrong can mean expensive redesign.

Fire doors and the 2029 changes

The 2026 booklet focuses on escape; the doorset changes arrive with the 2029 amendments. From 2 September 2029, the remaining references to the national BS 476 fire-resistance classes are removed from AD B. Fire resistance will be specified through the European route — products tested and classified to BS EN 13501, with fire doorsets tested to BS EN 1634-1/2/3.

During the transition, doorsets already tested to BS 476 can continue to be used, and the familiar FD30 / FD60 designations remain current in the meantime. For existing buildings, the practical duties are unchanged and immediate: fire doors in escape routes must be in working order, self-closing, and free from modifications — see our guide to fire door legal requirements.

What responsible persons and landlords should do now

Whether you own a single block or manage a portfolio, the September changes are a prompt to review, not panic:

Check your fire risk assessment is current — at least annually, and after any significant change to the building or its occupants.
Review the evacuation strategy. If your block is over 18 metres with a single common stair and a stay-put strategy, make sure that strategy is documented and justified in the FRA.
Keep escape routes and lobbies clear and fire doors in good order — wedged-open doors remain one of the most common failings found at inspection.
Plan for residents who need assistance — evacuation lifts, refuges and PEEPs should be reflected in the building's fire safety arrangements.
If you're planning building work, get a fire strategy review before committing to a layout, not after.

How HawkSwift can help

HawkSwift's NEBOSH-qualified assessors carry out fire risk assessments for blocks of flats, HMOs and commercial premises across the UK. We review escape provision against current guidance — including the 2026 changes — and provide plain-English reports within 48 hours, from £199 + VAT.

If you need to understand how the Approved Document B changes affect your building, book a fire risk assessment or ask us about a fire strategy review. You can also read our guide to choosing a fire risk assessment company before you appoint anyone.

*This article provides general guidance and is not formal legal or design advice. For specific projects, consult your building control body or a registered building control approver.*

Frequently asked questions

Does every block of flats over 18 metres now need two staircases? From 30 September 2026, Approved Document B recommends that new blocks of flats with a top storey 18 metres or more above ground level are served by more than one common staircase. It is guidance supporting the Building Regulations, so departures are possible but must be justified by fire engineering. It does not automatically apply to existing buildings.

When does the second staircase rule come into force? 30 September 2026, with transitional provisions. Projects with a building notice, initial notice or full-plans application made before that date can continue under the previous guidance if the work is sufficiently progressed by 30 September 2026 or within 18 months of it.

Do the 2026 changes apply to existing buildings? Not as a retrofit requirement. Existing blocks are assessed on their actual construction and fire precautions, and the fire risk assessment under the RRO 2005 continues to be the key document. Alterations and changes of use must not make existing conditions worse.

How is the 18-metre height measured? Using the method in Approved Document B, to the top storey — not the roof height, parapet height or the height quoted in planning documents.

Is Approved Document B a law? No. It is statutory guidance showing one way to meet the functional requirements of the Building Regulations 2010. Alternative solutions are possible through a properly documented fire-engineering approach.

Do care homes need sprinklers now? Under the 2025 changes to Approved Document B, all new care homes need automatic sprinklers irrespective of height, with compartment sizes limited to 10 beds and self-closing devices on doors. See our guide to care home fire safety and CQC alignment.

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