Second staircases in tall residential buildings – Where are we now?

You may recall that we looked at the changing position in relation to the requirement for second staircases in tall residential buildings in one of our previous blogs. At that time developers were still faced with uncertainty surrounding the technical requirements for second staircases in tall residential buildings. Much of that uncertainty was recently removed with the publication of the amendments to Approved Document B, which now clarifies that, from 30 September 2026, all residential buildings over 18 metres high must have two staircases. Here we take a brief look at the new requirements and consider the potential impact.

Changing thresholds

As a reminder, the government had initially consulted on a requirement for second staircases in new residential buildings over 30 metres in December 2022; the Mayor of London also confirmed at that time that a threshold of 30 metres would apply to residential developments in London with immediate effect. However, the government then confirmed in July 2023 that the height limit would in fact be 18 metres (which is in line with the threshold for a "higher-risk building" under the Building Safety Act 2022). No technical building regulations guidance was forthcoming at that time. This caused many schemes to be put on hold while developers waited for the detail to be published.

New technical guidance

At the end of March 2024, the long-awaited amendments to Approved Document B: Fire Safety were published. This technical guidance now states that residential buildings over 18 metres in height should have more than one common stair. The guidance confirms that interlocked stairs (otherwise known as scissored or stacked stairs) count as one stair. The guidance does not, however, include an absolute requirement for evacuation lifts, though this was an issue that fire chiefs had been campaigning for (although note that evacuation lifts are a requirement of the London Plan).

Transition period

The new guidance does not apply immediately – the changes do not take effect until 30 September 2026. The previous version of Approved Document B continues to apply where a building control application (either by way of a building notice, an initial notice or full plans application) has been made to the relevant authority before 30 September 2026 and the building work to which it relates:

• "has started and is sufficiently progressed before that day; or
• is started and is sufficiently progressed within the period of 18 months beginning on that day" (ie, 30 September 2026).

The definition of "sufficiently progressed" is the same as that found in the Building (Higher-Risk Buildings Procedures) (England) Regulations 2023. A new building is to be treated as sufficiently progressed when the pouring of concrete for the permanent placement of the trench, pad or raft foundations has started, or the permanent placement of piling has started. Where works relate to an existing building, it is sufficiently progressed simply when that work has started; or where the building work consists of a material change of use of a building, it is sufficiently progressed when work to effect that change of use has stated.

Potential impact?

Given the impact on scheme viability of giving valuable floorspace over to an additional staircase, developers and investors may be pleased to see that the transitionary period allows plenty of time for current developments to continue to be built with one staircase alone. The government has stated that there is no suggestion that existing and upcoming single-staircase buildings are inherently unsafe as long as they have been built in accordance with the previous versions of Approved Document B and other relevant standards, and have also been well-maintained and properly managed.

However, concerns have been expressed that the changes to Approved Document B could result in an emerging secondary market, as potential buyers and occupiers shy away from single staircase buildings. Therefore, despite the transition period, many developers and investors may now be reviewing their planning application proposals to look to provide the second staircase prior to the requirement becoming mandatory.

For further information please contact: