InSite | B4 Requirements for Buildings of Any Height

B4 Requirements for Buildings of Any Height

In December, there were significant changes made to the Building Regulations in respect to the use of combustible materials in external walls of ‘relevant’ buildings (for example: a residential building having a floor level exceeding 18.0m above external ground level).


These changes were developed in a manner that was to work alongside (and not instead of) the pre-existing requirement B4-(1) of Schedule 1, Part B of the Regulations - the requirement being:


“The external walls of a building shall adequately resist the spread of fire over walls and from one building to another, having regard to the height, use and position of the building.”


It’s important that, despite the focus in recent months on buildings over 18m, we, as an industry, don’t lose sight of requirement B4-(1) and how it relates to buildings of all heights, and not just those over 18m.


The December 2018 amendments to the regulations included a detailed definition of the elements that constitute an ‘external wall’.


The MHCLG issued a Circular Letter titled ‘Requirement B4’, July 2019. The letter reminds Building Control bodies that they should use judgement to consider the overall intent of the B4 requirement for buildings that are less than 18.0m, particularly where the guidance in the approved document is not specific. The letter acknowledges that the use of combustible materials within or attached to the external walls of buildings below 18.0m in height are not expressly prohibited (either by the Building Regulations or the Approved Documents), but notes that it is still necessary to consider the health and safety risk in these buildings from fire spread.


The letter concludes: “Where Building Control Bodies consider that the extent and arrangement of materials and/or attachments to an external wall may not meet the functional requirement of B4, they should raise this with the person carrying out the work and request further evidence to show that reasonable provisions will be made to meet Requirement B4.”


It is important that all departments and individuals in the construction and development of new homes, whether construction, surveying, project management, risk assessment, and so on, are familiar with the requirements of B4 and that these requirements are being applied.


On projects for which Premier Guarantee are providing building control, our building control team will carry out the necessary design checks and request that the surveyors confirm that the agreed fire safety elements are being installed in an appropriate manner.


On projects on which Premier Guarantee are only providing structural warranties, we will ensure that reasonable provisions are made to meet Requirement B4. This may result in an assessment and a request to the developer for evidence to confirm that B4 requirements have been met.


Please see below for the link to the MHCLG Circular Letter: