Government Bans Combustible Materials in External Walls of Tall Buildings
5 Dec 2018
The Concrete Centre’s principal structural engineer and expert on fire, Tony Jones, clarifies the Government’s combustible materials ban and its impact on construction.
On 29 November the Government announced details of the changes to the Building Regulations, and associated guidance, that bans the use of combustible materials in the external walls of the relevant buildings. The changes are comprehensive, affecting regulations 2, 4, 5, 6, and with the main part in regulation 7. In addition, a revision to the Approved Document B has been issued.
The buildings covered by the ban include any building with a storey 18m above the ground that either contains a dwelling, a room for residential purposes or contains an institution. It is clarified that student accommodation; care homes; dormitories in boarding schools; and hospitals with storeys above 18m are included, although hotel-type uses are not covered. The new regulations come into force on 21 December 2018, although there will be some leeway for some buildings already in the planning process, providing construction starts within two months of the ban.
The changes to regulation 2 are aimed at providing clarity for the wall components affected, and anything within the wall is covered. Structure within the external wall of the relevant buildings will, therefore, need to be non-combustible. In addition, certain specified attachments such as balconies, which will also be covered by the ban, are defined.
The changes for regulation 4 confirm that the ban applies to work carried out to upgrade the thermal performance of the relevant buildings whilst the changes to regulations 5 and 6 describe how the ban will work where there is a material change of use. Any building that, through modification, falls into one of the relevant building types will need to comply with the ban.
Regulation 7 provides the details of the ban, and states that the materials in the external walls of buildings need to comply with European Classification Class A2-s1, d0 or A1. It should be noted that the A2 limited combustibility class used in the external walls of the relevant buildings is different to that in Appendix A of Approved Document B which allows the lower performing A2-s3 d2 class, so specifiers will need to take care here. Regulation 7 acknowledges that a number of items used in the external walls may not be readily available in a non-combustible form and a relatively short list of items exempt from the ban is given.
The list includes specific items like cavity trays between two leaves of masonry, seals, gaskets, fixings, sealants and backer rods. However, there are more generic items such as window and door frames, and thermal break materials required to meet the thermal bridging requirements of Part L of Schedule 1. It is accepted that the list will need regular review and the proposal is to carry out such a review every year rather than every five years which is more normal for Approved Documents.
Overall the changes to the regulations have delivered the type of ban that was expected. The practical impact on change of use of existing structures will need to be considered. In addition, the completeness of the list of excluded items will be tested. The point being that as these areas are written into the regulations there is no way around the requirements.
Principal Structural Engineer - Tony Jones
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