The second staircase requirement

In short: New residential buildings in England over 18 metres must be designed with a second staircase. The requirement becomes mandatory from 30 September 2026, following an update to Approved Document B published on 29 March 2024. The 18 metre threshold deliberately aligns with the higher-risk building definition under the Building Safety Act 2022.

What's changing

Government guidance now expects new residential buildings above 18 metres to have two staircases, rather than relying on a single-staircase design. It is a design and fire-strategy change aimed at improving evacuation and firefighting access in tall residential buildings.

When it applies

• The updated Approved Document B guidance was published on 29 March 2024.
• There is a transitional period. From 30 September 2026, new building-regulations applications for in-scope buildings must follow the new (two-staircase) guidance.
• Schemes that gained building-regulations approval under the previous single-staircase guidance before 30 September 2026 are not required to add a second staircase - but those projects must have started construction "in earnest" by around 30 March 2028 to keep the benefit of the old rules.

Who it affects

This is primarily a matter for developers, designers and clients bringing forward new tall residential schemes - it shapes design, cost and programme. It sits alongside the wider Gateway regime for higher-risk buildings, where the Building Safety Regulator is the building control authority.

How CTS helps

CTS supports clients on the building-safety implications of new higher-risk buildings - coordinating the fire strategy and evidence, and making sure design decisions like this are captured in the golden thread from the outset, so the building is straightforward to register and manage in occupation.

General information, not legal advice. Reviewed by the CTS building safety team.