Question to the Department for Levelling Up, Housing & Communities:

To ask the Secretary of State for Housing, Communities and Local Government, with reference to paragraph 7.9 of Approved Document B of the Building Regulations 2010 (2019 edition), whether a rooftop extension and the building the extension is constructed on, are considered to be separate parts for the purposes of a fire risk assessment of the building and therefore for the requirement for a sprinkler system.

For the purposes of Approved Document B, 'separated part' is defined in Appendix D, Diagram D5 of that document. This provides that a separated part should be separated from another part of the same building by a compartment wall, to the full height of the part, in one vertical plane. This is unlikely to apply to a rooftop extension.

It is the responsibility of those undertaking the building work to demonstrate the regulations are met, and each building project should be considered individually. We have published advice on this subject in a circular letter which can be found here:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/887227/Approved_Document_B_May_2020_amendment_-_Circular_letter_2020.pdf .