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Single Stair High Rise Residential Buildings – How High is Too High?

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For a number of years and with increased urgency following the Grenfell tragedy in 2017, the provision and suitability of single staircase high rise residential buildings has rightly been called into question. Recent reports highlighting concerns raised by the London Fire Brigade (LFB), over plans for high rise ‘single stair’ residential building proposals, including a 55 storey development, have come to light.

Current guidance permits residential buildings of any height to be built with a single staircase however, opinions on what is considered ‘acceptable’ in terms of occupant and building safety is seeing planning applications ‘pushed back’ to developers, who are being told to rethink their proposals.

The issue of fire safety is multi faceted and no single action or change to legislation will solve the problems faced by the construction industry. A holistic approach is required to ensure the safety of premises throughout their entire lifecycle, but is driven ultimately from the outset by robust and comprehensive guidance.

The revised edition of BS 9991 Fire safety in the design, management and use of residential buildings, published in draft format in August 2021 proposes significant change to the design of single stair residential buildings.

What is being proposed

Amongst a number of proposed amendments to the BS 9991, changes to the design of single stair residential buildings have been put forward for comment. The most obvious and relevant to this post is the differentiation that has been made between buildings with a single stair and a floor level between 11m and 18m and those buildings with a floor level above 18m.

In the draft document it is proposed that residential buildings with a floor level above 18m with a single stair be provided with a pressurization system (in accordance with BS EN 12101-6), providing protection to the staircase, firefighting lift shaft and lobby. Current guidance places no such requirement on building designers.

These changes will force building designers to consider their approach. Whilst some developments would likely proceed with a single stair design, provision of a pressurization system would add an extra level of safety that would help to maintain a smoke free stair in the event of a fire. It is likely that the intention is to ‘encourage’ designers to go down the route of adopting a second staircase within the design resulting in an alternative escape route being available should one stair become compromised. The two staircase design has the benefit of enabling simultaneous firefighting in one stair and evacuation of building occupants via the second.

Although at the time of writing this post, the changes proposed in the draft document have not been carried through into published guidance, were they to be, it would see a significant and positive step in the drive towards safer residential buildings.

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