The second staircase changes to Approved Document B take effect in England on 30th September 2026. For anyone working on a block of flats, the useful question is not just when the guidance changes. It is whether the design, building control submission and construction programme put the scheme on the right side of the transition.
The changes were published in 2024. They are not a new announcement this month, and having planning permission is not enough to preserve the previous building control guidance.
A second staircase can also change the scheme that received planning permission. That deserves an early check, but it does not automatically mean a fresh planning application.
Which buildings need a second staircase?
The specific new provision is in Approved Document B Volume 1 and concerns blocks of flats with a storey 18 metres or more above ground level. The updated common-stair guidance calls for more than one common staircase at that threshold.
It is not a blanket new rule for every building described as residential. Hotels, care homes, ordinary houses and other accommodation have their own applicable fire-safety guidance. Student accommodation and similar schemes need to be assessed by their actual layout and use: calling a development student housing does not establish whether it contains flats.
Nor does a building below 18 metres automatically qualify for a single stair. Other restrictions in the escape guidance can require more than one.
The 2026 amendment booklet also confirms that interlocked or scissor stairs count as one escape stair, not two independent alternatives.
How is the 18m height measured?
Use the height of the top storey in Diagram D6, rather than the height to the roof or parapet. The measurement runs from ground level on the lowest side of the building to the upper floor surface of the top storey.
Rooftop plant areas and a top storey consisting exclusively of plant rooms are excluded. A roofline reaching 18 metres is therefore not, by itself, the answer to this test.
The threshold is inclusive: 18 metres or more, not just buildings exceeding 18 metres. Do not substitute the separate higher-risk-building definition, which includes an alternative storey-count test. This staircase provision does not have a seven-storey alternative.
The current documents are available through the Government’s Approved Document B publication page. Some collated editions include future amendments as well as current guidance, so check the commencement notes rather than assuming every paragraph already applies.
What must happen before 30th September?
There are two parts to the transition.
First, before 30th September 2026, a building notice or initial notice must have been given to the relevant authority, or a building control approval application with full plans must have been made to it.
This concerns the appropriate building control submission, not a planning application or a planning permission. The wording does not require the building control approval itself to have been granted before that date.
However, that does not make every submission route available to every project. Higher-risk building work normally needs the Building Safety Regulator’s approval before work starts. An unavailable building-notice route is not a shortcut.
Second, the work must have started and been sufficiently progressed before 30th September 2026, or must start and be sufficiently progressed within the 18-month period beginning on that date.
A timely submission without the required progress does not preserve the old guidance indefinitely. Check both the submission evidence and a realistic construction programme.
What counts as sufficiently progressed?
For construction of a new building, the test is met when pouring concrete for the permanent trench, pad or raft foundations has started, or permanent placement of piling has started.
For work to an existing building, that work must have started. Where the work is a material change of use, work to effect that change of use must have started.
For a new building, clearing the site, erecting fencing or excavating alone is not the published foundation or piling test. Conversely, the transitional wording does not require all foundations and the ground-floor structure to have been completed.
This matters because the ordinary legal commencement test used for building control lapse is different. Regulation 46A of the Building Regulations 2010 sets out that separate test for England.
Our Building Regulations guide explains the wider approval and commencement framework. Do not move a definition from one regime into another.
Keep dated records of the qualifying works and agree the evidential position with the relevant building control body. Nothing in the transition authorises an early start contrary to planning conditions, building control requirements or other necessary approvals.
Does this apply retrospectively to existing blocks?
The amendment does not impose an automatic obligation to retrofit a second staircase into every existing block. But a conversion, extension, material alteration or material change of use is not necessarily outside Building Regulations merely because the building already exists.
The applicable requirements depend on the work. Have the fire strategy and the building control position assessed for that particular scheme rather than relying on a simple new-build-versus-existing label.
There is also a distinction between the law and the guidance. The functional fire-safety requirements sit in the Building Regulations 2010, Schedule 1. Approved Document B gives guidance on satisfying them; it is not the only possible compliant design method. An alternative approach still needs a properly justified demonstration of compliance.
Sections 6 and 7 of the Building Act 1984 explain the status of Approved Documents. Following, or departing from, relevant guidance can be evidence in proceedings about compliance with Building Regulations. That does not make the guidance optional in the everyday sense of being something a design team can simply ignore.
What changes alongside the staircase?
The 2026 booklet also addresses evacuation shafts and, where evacuation lifts are provided, protected lobbies, access arrangements and smoke protection. It also changes guidance on common-stair width and the routes to alternative stairs.
For blocks of flats with a storey 18 metres or more above ground level, the new common-stair guidance specifies a minimum clear width of 1,100mm between walls or balustrades. Handrails and strings projecting no more than 100mm on either side may be disregarded for that measurement.
The design team should therefore check the whole core and escape strategy, rather than simply drawing an extra flight of stairs.
This booklet does not introduce a universal requirement for an evacuation lift in every affected block. Its relevant provisions address arrangements where those lifts are provided. Other applicable standards or planning requirements still need checking.
The Government’s September 2024 circular letter explains the reissued amendment package. Circular 04/2024 replaced the earlier staircase circular to put the changes in chronological order, with minor typographical corrections. It did not shift the staircase implementation date.
Separate care-home sprinkler changes took effect in March 2025, while other amendments have a 2029 date. They should not all be presented as new requirements arriving on 30th September 2026.
Will the planning permission need changing?
Possibly. A second staircase can affect floorplans, the lift and stair core, elevations, the number of homes, massing and viability. Those are potential consequences of the design work, not automatic outcomes in every case.
Start with the permission’s description, approved drawings and conditions. A wholly internal rearrangement may not itself be development, but an approved-plans condition or other requirement can still be relevant.
A non-material amendment under section 96A may be appropriate where the change is genuinely non-material in context. Previous changes under that section also form part of the assessment.
A section 73 application may provide a route to change conditions, including an approved-plans condition. It cannot simply rewrite the operative description of the development.
A fresh application may be needed where the resulting proposal cannot properly be dealt with through an available amendment route. Equally, an additional stair does not automatically require fresh permission.
The practical approach is to review the fire design, building control transition and planning drawings together. Finding a compliant technical solution is only part of the job if it no longer matches the permission you intend to build.
Prepared: 7th September 2026
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