Change to Part B targets greater safety

Recent changes to Approved Document B are designed to improve fire safety in buildings – but although they go some way to clarifying the regulations, there is still work to be done


  • John Miles

08 April 2021

On 26 May 2020, the Ministry of Housing, Communities & Local Government (MHCLG) announced changes to both volumes of Approved Document B, the 2019 editions of Fire safety: Volume 1 – Dwellings and Volume 2 – Buildings other than dwellings. These amendments affect sprinkler provision and wayfinding signage in blocks of flats with a storey above 11m, whether they are new-build or existing residential buildings that gain a storey above 11m as a result of alterations, as measured in accordance with diagram D6 in Approved Document B.

These changes took effect on 26 November 2020 and apply to England only. If applications have been submitted before that date then, unless work commenced on site before 29 January this year, the design must be altered to incorporate the necessary amendments.

The movement of the sprinkler threshold down from 30m to 11m in requirement B3 is a significant and welcome step. The regulations will also have a greater impact because they now apply to residential buildings containing flats formed by a material change of use, extension or material alteration, as well as to new buildings.

While the document doesn't specifically refer to existing stock in applying the guidance, it does state that an existing building above 11m needs to be considered if any alteration works – including material alterations, material changes of use or extensions – are likely to increase fire risk.

Additional storeys

Adding new storeys to a building presents a number of challenges, particularly if this takes it above 11m in height. In developing a policy note for our surveyors on the changes, Assent Building Control asked MHCLG for clarification on this issue in a private letter.

The ministry replied: "Sprinklers should be provided for a new build over 11m and new flats formed over 11m on an existing building. The provision of sprinklers in the rest of the building is a matter to be considered carefully on a case-by-case basis."

MHCLG's circular of 26 May 2020 on the application of Building Regulations where further storeys are added to existing buildings advises that: "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."

It adds: "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 …. Equally, it will be necessary to … ensure that the level of fire protection in the building as a whole is made no worse."

However, a further circular of 10 August 2020 states: "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. This may not always be set out in the approved documents and building control bodies should consider carefully the application of the Building Regulations to these projects."

This means there is a possibility of confusion and inconsistency as to whether the whole building requires sprinklers.

"Adding new storeys to a building presents a number of challenges, particularly if this takes it above 11m in height"


Sprinklers should be installed in any building to which the revised Approved Document B applies, whether explicitly or by implication. Appendix E of volume 1 states that sprinkler designs should be installed throughout a building or "separated part"; that is, in each apartment.

Unfortunately, Approved Document B's definition of a "separated part" – "Part of a building that is separated from another part of the same building by a compartment wall [where] the wall runs the full height of the part and is in one vertical plane" – means that a roof extension cannot be regarded as such, because it is generally divided by a compartment floor rather than a compartment wall. The intentions of the regulations and wording are difficult to align in this case.

In practice however, if we don't follow the intention behind the Building Regulations' requirements and sufficiently demonstrate our decision-making on compliance, we could come into conflict with the fire service, fail to satisfy post-completion surveys such as EWS1 forms, and subsequently face potential legal battles.

It should be noted that, although building control surveyors do provide professional advice, our remit is limited to confirming compliance with the Building Regulations. If we exceed this then we are more likely to expose ourselves to risk.

Additional considerations

Existing buildings often present additional complexities when it comes to considering how to install sprinklers, because freeholders will have to negoitate to gain access under leases' repair and maintenance clauses to fit systems where they are required.

In addition, if as a result of conversion works a building also exceeds 18m in height then other fire safety requirements relating to facade build-up and access need to be fulfilled as well, such as installing firefighting lifts and ensuring that the facade meets the requirements of Regulation 7(2).

The other 2020 amendments to Approved Document B affect the way we navigate a building, and require the inclusion of wayfinding signage for new residential blocks. The inclusion of such signage not only supports residents but also, crucially, helps the fire brigade identify floors and flats throughout the common parts of the building when they need access.

Collective will

Although the guidance from MHCLG has not been explicit about the consequences of the regulatory changes for existing buildings, there is a collective will in the construction industry to do things right.

The provision of mandatory sprinkler systems and consistent wayfinding signage in all new blocks of flats more than 11m tall is recoginsed as an important step in improving the building safety system, and protecting occupants of high-rise residential buildings.

RICS global buiding standards director Gary Strong comments: "The revision to the requirement for sprinklers in blocks of flats down to 11m from a proposed 18m threshold was the result of significant lobbying by RICS, in conjunction with the Royal Institute of British Architects and the Chartered Institute of Building."


Related competencies include: Fire safety, Legal/regulatory compliance

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