After three years of anticipation, the latest version of BS 9991:2024 Fire Safety in the Design, Management and Use of Residential Buildings – Code of Practice (bit.ly/CJBS9991) has been published. The draft version of the standard was first published in 2021, and the final version – published in November 2024 – has important implications for certain buildings.
It provides much-needed clarity on various elements that have long been considered ambiguous by designers, while also capturing several enhancements to bring the standard in line with wider industry developments.
This new standard supersedes BS 9991:2015 and should now be used as statutory guidance for residential projects in England, Wales and Northern Ireland. BS 9991 remains an alternative design standard to Approved Document B (for England), which provides guidance for the design of buildings to meet Part B – Fire Safety – requirements in Building Regulations. Although Approved Document B has been recommended by various relevant groups, such as the National Fire Chiefs Council and RIBA, it is not the most recent standard for designers.
Some of the BS9991 changes were aimed at making the guidance less England-centric. References to Approved Documents were removed as they only apply to England. A British Standard is intended to be applicable to the whole of the UK and we know other countries that base their own guidance on British Standards.
This latest version of the standard is more in line with industry expectations, providing guidance that will, hopefully, result in higher-quality fire safety design
BS 9991 is applicable to residential blocks of flats up to 100m in height, where the structure is of traditional, non-combustible materials, such as steel and concrete. It also covers residential buildings that are not made of traditional, non-combustible materials, up to a height of 11m.
For advocates of sustainable building materials, this is promising, as it increases the possibility of using materials such as mass timber and timber frame. It also unlocks potential for a greater volume of quality housing to be built in very tall buildings.
The changes outlined below are undoubtedly a positive step forward in enhancing fire safety. Currently, this represents the highest standard of fire safety, featuring clearer guidance, increased emphasis on accessible design, and a broader scope in this year’s edition. The right changes are beginning to be made, but the standard will, hopefully, continue changing and evolving to reach even greater heights in the future.
Internal planning of flats
For the design of open-plan flats, recommendations now incorporate a 1.8m clear zone around cooking equipment to allow occupants to escape through the living/dining space, as is established industrypractice.
In addition to this, the outdated and onerous requirement for enclosing kitchens in open-plan flats larger than 8m x 4m has been removed. New guidance now also recommends that charging points for mobility scooters or electric wheelchairs are not located in an apartment’s entrance hallway.
Evacuation lifts
Where a residential building provides lifts, it is now required to also provide evacuation lifts. This is another welcome addition for inclusive design, as BS 9991 goes beyond comparable upcoming Approved Document B amendments. The standard goes into detail on the specifications needed to implement these accessibility features successfully.
Design of common escape routes
BS 9991 recommends that any residential building with a storey height above 18m should have at least two escape staircases. This brings it into alignment with upcoming amendments to Approved Document B. A single-stair approach is still acceptable for buildings less than 18m.
In the previous iteration, BS 9991:2015, the diagrams for common escape routes in Figures 6 and 7 were inadequate, and failed to cover many situations where the internal corridor design was more complicated. The new standard provides additional clear example arrangements, giving designers more certainty going forward.
Suppression
Sprinkler protection is now required in all residential buildings above 11m, bringing BS 9991 in line with Approved Document B. However, it still allows buildings up to 30m with sprinklers to be provided with 60 minutes of structural fire resistance, instead of 90 minutes.
References to the BS 8458 standard relating to water-mist systems in residential buildings have been removed from BS 9991, which, by omission, means residential buildings should be protected with sprinkler systems. Where water mist is proposed, therefore, it is now considered a fully fire-engineered solution that will be a derogation from guidance.
Residential building smoke control
For buildings more than 18m in height, only natural or mechanical smoke shafts are now recommended, and external automatic opening vents direct to the outside of the building will not be acceptable. Above 30m in height, only mechanical smoke shafts (either extraction or pressurisation) should be used for the protection of stair lobbies, and natural smoke shafts in these circumstances will no longer be acceptable.
Guidance for care homes
Sprinklers will be required in all care homes regardless of storey height and should either be in accordance with BS 9251:2021 or BS EN 12845:2015.
There are specific recommendations for maximum travel distances in care homes depending on the dependency of residents. For low- and medium-dependency residents, travel distances to the nearest relative place of safety should be 15m for single-direction escape and 32m for multi-direction escape. For high-dependency residents, this is 12m and 25m respectively.
This latest version of the standard is more in line with industry expectations, providing guidance that will, hopefully, result in higher-quality fire safety design. This should lead to greater consideration of inclusive design and sustainable material selection options for the workplace.
- Calum Smith is a senior engineer at Cundall
