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BS 9991:2021 DRAFT is out for consultation

Fire Engineering By Andy Bishop, Partner, Building Services – 09 November 2021

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Andy Bishop

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BS 9991 is the code of practice for fire safety in the design, management and use of residential buildings. It complements BS 9999 which is the code of practice for non-residential buildings.

BS 9991 is intended to help people put suitable fire safety measures in place in residential buildings, such as fire detection and alarm systems, fixed fire-fighting systems and so on.

It gives recommendations and guidance on the design, management and use of residential buildings in order to achieve reasonable standards of fire safety for people who are in and around them and fire-fighters.

BS 9991 provides guidance on the management of fire safety during the whole lifecycle of a building. It applies to the design of new buildings and to material alterations, extensions and material changes of use to existing buildings.

This long-awaited new version of BS 9991, used as the basis of fire strategies for blocks of flats, introduces considerable changes that will impact the design of and systems in residential buildings. The full release for this standard is unlikely to happen until late 2022 but we have summarised below some of the more notable changes contained in the draft.

Applies to all residential buildings

  • In all developments where passenger lifts are installed, at least one lift should be an evacuation lift.
  • Secondary power supplies – The previous document was suitably ambiguous when it came to the design of secondary power supplies, and usually created much debate within the design team over what was and was not suitable. This draft has taken steps to clarify the issue. The only acceptable arrangements for secondary power supplies are:
    • A generator
    • An independent high voltage supply, provided it is fed from an independent utility primary network substation to that feeding the primary supply
    • An uninterruptible power supply (UPS). The standard advises on the sizing of the UPS.

      Using a single intake with diverse routes and a life safety distribution board is no longer acceptable.
  • Cross referencing with the new residential sprinkler standard BS 9251:2021 (which has now been published), using a modified residential sprinkler system is acceptable for some ancillary areas such as retail, cafe, bin stores, plant rooms, car parks, etc. subject to a limit of 100 m2.
    • Any non-residential areas larger than this limit will require protection using a commercial BS EN 12845 system. i.e. separate sprinkler tank and pumps.

BS 9991 is the code of practice for fire safety in the design, management and use of residential buildings. It complements BS 9999 which is the code of practice for non-residential buildings.

BS 9991 is intended to help people put suitable fire safety measures in place in residential buildings, such as fire detection and alarm systems, fixed fire-fighting systems and so on.

It gives recommendations and guidance on the design, management and use of residential buildings in order to achieve reasonable standards of fire safety for people who are in and around them and fire-fighters.

BS 9991 provides guidance on the management of fire safety during the whole lifecycle of a building. It applies to the design of new buildings and to material alterations, extensions and material changes of use to existing buildings.

This long-awaited new version of BS 9991, used as the basis of fire strategies for blocks of flats, introduces considerable changes that will impact the design of and systems in residential buildings. The full release for this standard is unlikely to happen until late 2022 but we have summarised below some of the more notable changes contained in the draft.


Applies to all residential buildings

  1. In all developments where passenger lifts are installed, at least one lift should be an evacuation lift.
  2. Secondary power supplies – The previous document was suitably ambiguous when it came to the design of secondary power supplies, and usually created much debate within the design team over what was and was not suitable. This draft has taken steps to clarify the issue. The only acceptable arrangements for secondary power supplies are:
    1. A generator
    2. An independent high voltage supply, provided it is fed from an independent utility primary network substation to that feeding the primary supply
    3. An uninterruptible power supply (UPS). The standard advises on the sizing of the UPS.

      Using a single intake with diverse routes and a life safety distribution board is no longer acceptable.
  3. Cross referencing with the new residential sprinkler standard BS 9251:2021 (which has now been published), using a modified residential sprinkler system is acceptable for some ancillary areas such as retail, cafe, bin stores, plant rooms, car parks, etc. subject to a limit of 100 m2.
    1. Any non-residential areas larger than this limit will require protection using a commercial BS EN 12845 system. i.e. separate sprinkler tank and pumps.


Residential buildings over 11m

In line with changes to the Approved Documents, sprinklers will be required for all residential buildings over 11m in height. However, the standard advises that all areas must be protected, including corridors and stairs even if they are sterile.

  1. Single-stair high-rise buildings will only be acceptable if:
    1. The stair is provided with a pressurisation system
    2. Structural protection is increased from 60 minutes to 90 minutes fire resistance (FR)
    3. Timber structure is not acceptable
    4. An additional lobby needs to be provided between the stair and corridor affording access to the flats (similar to current arrangements in Scotland)
    5. Stairs should be wider - 1.2m
    6. If extended corridors are present, additional mechanical smoke extract may be required in addition to the stair pressurisation
  2. Buildings over 18m in height require two evacuation lifts.
  3. An evacuation alert system is required for buildings over 18m with a stay put policy. Systems to BS 8629 provides sounders in apartments connected to a central fire alarm panel – this can be used by the fire service to raise an evacuation alarm in specific or all flats. This is not in any way automatic or connected to detectors and is only for the use of the fire service (already required in Scotland).

Residential buildings over 30m

Natural smoke shafts are no longer acceptable.


Further notes on evacuation lifts

Additional lifts may be required depending on the building layout.

  • In some cases, fire-fighting lifts need to be separate to evacuation lifts.
  • Secondary power will be required, as above, so a generator or alternative will be required to all buildings even if no other fire safety systems are present.
  • The lifts will need to be accessed from a separate lobby adjacent to the stair that does not serve the main corridors directly.
  • The standard provides the first definitive guidance on operation and programming of evacuation lifts in residential buildings. In most cases, it is likely they will need to have an automatic evacuation mode as well as the standard driver assisted mode.
  • These requirements are also largely aligned with the London D5 planning policy requirements.

WARNING: THESE COMMENTS APPLY TO THE DRAFT AND MUST NOT BE REGARDED OR USED AS THE BRITISH STANDARD.

For more information on what services the Cundall fire team can offer don’t hesitate to get in touch.

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