SWECO BUILDING STANDARDS GUIDANCE NOTE
Material Alterations Increasing Height Providing Residential use over 11m
Introduction
Where buildings are extended in height to provide dwellings above 11m where previously there was none, Sweco’s Guidance is that the whole building should be sprinklered unless adequate mitigation is provided.
BS 9991 2024 has supported this view and is explicit in saying that this form of extension should result in the sprinkler system being extended to the whole building. The new 9991 has also increased the expectation of “whole building” to include the stairs, common corridors and lobbies, Approved Document B looks for the sprinkler system to be provided to the existing flats only.
Guidance
It is recognised in many instances access to install sprinklers in flats, not in the control of the client, will be resisted by existing lease holders. In this event the design team may make a proposal that does not include the provision of sprinklers to the existing flats, in this circumstance the design team would need to provide justification for their omission. As the proposal is not following the guidance in either ADB or BS 9991 the design team are left with the option of substantiating their scheme through a Fire Engineered approach in accordance with BS 7974.
In all cases the building should be considered as a whole and all risks to life considered.
The robustness of construction should be evaluated; concrete floors/masonry separation is likely to b
e more robust than joisted/stud construction in terms of compartmentation and structural fire resistance.
If flats have no suppression the adequacy of the protection to protected stairs should be considered.
- Is a protected corridor adequate protection to the staircase?
- Would an additional lobby or other enhanced passive features be beneficial?
- Would additional or enhanced smoke ventilation be beneficial?
- Could the sprinkler system be provided into the existing common and ancillary areas?
- Would additional firefighting/evacuation provisions be of benefit, such as:
- Evacuation alert system
- Firefighting shaft
- Evacuation shaft/lift?
The guidance would call for wayfinding in the stairs and the provision of a Premises Information Box in all cases so these facilities would not be seen as mitigation.
Externally, consideration should be given to the potential of an uncontrolled fire breaking out of an external window and the plume playing over openings within a different compartment/residence or potential spread over or through the external wall system.
The government guidance, on the matter is not definitive. The sentence, “This means ensuring that the standard of fire protection for the occupants of the new accommodation is as would be provided for a new building under the approved document.”, does not confine itself to the protection afforded within the flat.
It is Sweco’s view that it infers the fire protection from the common parts should be as for a new building, and that the risk to common parts in a new building is limited by the accommodation having sprinklers. As stated previously, it is Sweco’s view, that the process of “considering on its own merits” where the guidance on installing sprinklers through out the existing building cannot be followed, means the principles in BS 7974 should be followed by a competent fire engineer.
Government Publications
https://www.gov.uk/guidance/approved-document-b-fire-safety-frequently-asked-questions
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The Guidance Note does not constitute professional advice and Sweco hereby offers no reliance and accepts no liability (in contract, tort (including negligence) or otherwise) for parties acting on the content of this Guidance Note without taking specific professional advice from Sweco. The Guidance Note is provided as generic guidance only and any opinion, views or advice expressed in this Guidance Note are made without any representations or provide any assurances or warranties as to the content. If you require specific advice with respect to your own project or circumstances, please contact Neil Badley.