Second staircases from 30 September 2026: what residential project teams should check now

What changed on 30 September 2026?

The 2026 amendments to Approved Document B (Fire Safety) now take effect in England. The main change for residential development is a new height threshold for the provision of a second staircase in blocks of flats with a storey 18 metres or more in height.

The guidance also restructures parts of Section 3 dealing with means of escape and introduces concepts and terminology connected with evacuation shafts and evacuation lifts.

Approved Documents are statutory guidance on ways of meeting the Building Regulations. They are not, by themselves, a separate code of law. However, they are an important benchmark for demonstrating compliance, so a project departing from the guidance needs a properly evidenced alternative compliance strategy.

Why this matters commercially

A second staircase is not a minor detail. On a live scheme it can affect core layout, net saleable area, structural design, fire strategy, MEP coordination, planning interfaces, cost and programme.

That means the issue is relevant well beyond the fire consultant or architect. Developers, design-and-build contractors, consultants, funders and commercial teams need to know which version of the guidance the project is relying on and whether the design and building-control strategy support that position.

Do existing projects have transitional protection?

Potentially, yes. The previous edition of the guidance can continue to apply where a building notice or initial notice was given, or a building control approval application with full plans was made, before 30 September 2026, and the relevant building work either:

• had already started and was sufficiently progressed before that date; or
• is started and becomes sufficiently progressed within the 18-month period beginning on 30 September 2026.

Project teams should therefore avoid relying on the age of a planning permission, appointment or construction contract as a shortcut. The transitional test is tied to the specified building-control route and the progress of the building work.

What does “sufficiently progressed” mean?

For a new building, the Government circular says work is sufficiently progressed when 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, the work itself must have started. For a material change of use, work to effect that change of use must have started.

The evidence of that progress may become important if the project later has to demonstrate why it was entitled to rely on the earlier guidance.

Contract and project risks to check

• Design responsibility: identify who is responsible for the fire strategy and for coordinating changes across architecture, structure and building services.
• Change control: check whether a redesign is a variation/change under the building contract or professional appointment, and what notice or instruction machinery applies.
• Cost: establish who bears additional design, construction and loss-of-area costs if the scheme needs a second staircase or related redesign.
• Programme: record any effect on design release, approvals, procurement and critical-path activities.
• Transitional evidence: retain the building-control application or notice, acknowledgements, commencement records, dated site records and evidence showing when the relevant work became sufficiently progressed.

What should project teams do now?

1. Identify schemes around or above the 18-metre threshold. Confirm the height assessment and the fire-safety design basis.
2. Record which edition of Approved Document B is being relied on. Do not leave that assumption implicit in the design file.
3. Check the transitional route. Confirm the date and type of building-control submission and whether the progress test has been or will be satisfied.
4. Preserve the evidence. Keep dated records supporting commencement and sufficient progress.
5. Review contractual allocation. If a redesign is required, establish responsibility for instructions, fees, additional work, delay and loss of efficiency before positions harden into a dispute.
6. Coordinate planning, design and building control. A compliance change that affects layout or massing may have wider project consequences.

The wider point

Building-safety changes increasingly sit at the intersection of technical design, regulatory compliance and commercial risk. A project that cannot clearly explain which regulatory guidance applies, why it applies and who carries the consequences of change is exposed to avoidable cost and dispute.