SWECO BUILDING STANDARDS GUIDANCE NOTE
Material Alterations Building Regulations – 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.
It is recognised in many instances access to install sprinklers in flats, not in the control of the client, will not be granted. If the design team proposes to not install sprinklers throughout the whole building a fire strategy would have to be provided to justify the omission. The strategy should consider the impact of an uncontrolled fire in the existing accommodation immediately below the new accommodation and also at the lowest level that communicates with any protected stairway.
It would be expected that the fire strategy provides additionality over guidance, to mitigate the absence of suppression. It should also consider the potential for both internal and external fire spread from an uncontrolled fire developing within accommodation.
Guidance
The robustness of construction should be evaluated; concrete floors/masonry separation is likely to be 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 be beneficial?
- Would additional or enhanced smoke ventilation be beneficial?
- 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.
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.
In all cases the building should be considered as a whole and all risks to life considered.
Unfortunately, the government guidance, which will follow 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.
Reference Documents
https://www.gov.uk/guidance/approved-document-b-fire-safety-frequently-asked-questions
1.1.1 24. I am undertaking work on an existing building which is below 11m, and adding a new floor which will exceed 11m in height, do I need to sprinkler the whole building or just the new floor?
Each case must be considered on its own merits, but it is likely that where additional storeys are added to an existing building, some work on the original part of the building will be necessary.
Applicants and building control bodies are reminded of the need to consider these new provisions sprinklers in relation to extensions as required by Regulation 4(1). New accommodation, formed by building work, should meet the relevant requirements having considered the guidance in the approved document. 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. In the majority of cases, therefore, sprinkler protection will be necessary in any newly formed accommodation that falls above the new 11m trigger height.
It may also be necessary to consider additional protection for the existing parts of the building where needed to ensure that the extension is compliant with the applicable requirements of Schedule 1. Equally, it will be necessary to satisfy regulation 4(3) by ensuring that the level of fire protection in the building as a whole is made no worse.
There may also be situations where the risk assessment for the building (provided under the Fire Safety Order) requires further work to be done. Regardless of the minimum requirements of the regulations there is, of course, merit in providing additional protection throughout the building.
Further advice can be found in the following circular letter.
Circular letter on Approved Document B volume 1 and 2
Extensions Applicants and Building Control bodies are reminded of the need to consider these new provisions in relation to extensions as required by Regulation 4(1). New accommodation, formed by building work, should meet the relevant requirements having considered the guidance in the approved document. 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. In the majority of cases, therefore, sprinkler protection and wayfinding signage will be necessary in any newly formed accommodation that falls above the new 11m trigger height.
It may also be necessary to consider additional protection for the existing parts of the building where needed to ensure that the extension is compliant with the applicable requirements of Schedule 1. Equally, it will be necessary to satisfy regulation 4(3) by ensuring that the level of fire protection in the building as a whole is made no worse. There may also be situations where the risk assessment for the building (provided under the Fire Safety Order) requires further work to be done. Regardless of the minimum requirements of the regulations there is, of course, merit in providing additional protection throughout the building.
The contents of this Guidance Note are confidential to Sweco and the intended recipient and are subject to copyright in favour of Sweco. The content of this Guidance Note must not be reproduced by any person (including the intended recipient) without the prior written consent of Sweco.
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.