Approved Document B Second-Staircase Changes
Tall residential buildings in England are changing in a fundamental way: new guidance introduces a requirement for a second staircase in buildings with a storey at or above 18 metres. It is one of the most significant building-safety design changes in years, and although it sits mostly outside the fire alarm engineer's remit, the evacuation strategy it supports is closely bound up with the fire alarm's job. Understanding the change, and where the engineer's part lies, is worthwhile. This guide gives an orientation.
The central point is that the Approved Document B second-staircase change adds escape resilience to tall new residential buildings — a building-design matter that shapes the evacuation strategy the fire alarm supports, without changing fire alarm design itself.
Who this is for
This is for competent fire alarm engineers who want to understand a significant building-safety change affecting the buildings they work in. The experience level assumed is competent engineer. Use this as orientation; the staircase provision is a building-design matter under Approved Document B, applied by building designers and fire engineers. The fire alarm follows BS 5839-1 and supports the building's evacuation strategy.
What the change requires
Updated guidance in England introduces a requirement for a second staircase in new residential buildings with a storey at or above 18 metres in height. The amendments to Approved Document B were published in 2024 and come into force on 30 September 2026, with a transitional period before then during which applications may follow either the current or the updated guidance. This is statutory guidance supporting the Building Regulations, applying to relevant new building work rather than existing buildings. The precise requirements and transition come from Approved Document B and the building design, which are the authoritative sources. The headline is simple: taller new residential buildings will need a second protected escape stair.
Why a second staircase matters
The reason behind the change is escape resilience. A second staircase provides an additional protected escape route in a tall residential building, adding resilience to the means of escape if one route is compromised — for instance by smoke or by firefighting operations. It is fundamentally a building-design and escape-strategy matter rather than a fire alarm design change. But the evacuation strategy the building adopts — which the fire alarm supports — sits within this wider fire safety design, so the two are connected even though they are different disciplines. How escape is provided comes from Approved Document B and the fire strategy, applied by the building designers and fire engineers.
Its limited effect on fire alarm work
For the fire alarm engineer, the honest position is that the direct effect is limited. The change is about escape routes and building design, not fire alarm design, so it does not alter how a fire alarm is designed or maintained. But the fire alarm supports whatever evacuation strategy a building adopts, and escape provision is part of the wider fire safety the fire alarm serves. From field experience, the useful thing for an engineer is awareness — knowing the change exists and what it concerns — so that escape-design questions are recognised as belonging to the building designers and fire engineers, not the fire alarm engineer. The fire alarm follows BS 5839-1; the staircase provision follows Approved Document B.
The engineer's understanding
The practical takeaway is again about knowing the boundary. Understand that the change concerns escape routes in tall new residential buildings, that it is a building-design matter coming into force with a transition, and that it does not itself change fire alarm design — though the fire alarm still supports the building's evacuation strategy. Verify specifics against Approved Document B, keep fire alarm work to BS 5839-1, and direct escape-design questions to the building designers and fire engineers. An engineer aware of the wider changes, without overreaching into them, works more coherently within the building's overall fire safety.
Common points to check
Recurring issues include confusion over what the change affects, an assumption it alters fire alarm design, and escape-design questions mistakenly treated as the fire alarm engineer's. Confirming the fire alarm supports the building's evacuation strategy and directing escape-design questions to the designers is the essential check.
When not to rely on this alone
When not to use this article: do not treat it as escape-design guidance for a specific building. That comes from Approved Document B, the fire strategy and the building designers; the fire alarm follows BS 5839-1.
Relevant standards
The staircase provision follows Approved Document B, statutory guidance supporting the Building Regulations; the fire alarm follows BS 5839-1, a code of practice. The legal duty for fire precautions in most relevant premises sits under the Regulatory Reform (Fire Safety) Order 2005. Separate the legal duty from the recommended methods, and always work to current editions.
Professional disclaimer
This is an educational and workflow resource for competent engineers and does not replace Approved Document B, the current British Standards, the building design, or competent judgement. It is orientation only; verify specifics against the authoritative sources.
Related documentation
Use this with Approved Document B, the current BS 5839-1 and the building's fire strategy. Keep fire alarm work to its standard, and direct escape-design questions to the building designers and fire engineers.