Circular letter regarding the application of requirement B4 of the Building Regulations 2010

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To:

The Chief Executive:

Unitary, Metropolitan, District and London Borough Councils in England

County and County Borough Councils in Wales

The Town Clerk, City of London

The Clerk, Council of the Isles of Scilly

The Sub-Treasurer, Inner Temple

The Under Treasurer, Middle Temple

The Head of Building Control:

Unitary, Metropolitan, District and London Borough Councils in England

County and County Borough Councils in Wales

City of London

Council of the Isles of Scilly

Approved Inspectors cc: The Chief Executive:

County Councils in England

National Park Authorities in England & Wales

Chair: National Fire Chiefs Council

1July 2019

Dear Sir or Madam

Requirement B4

The purpose of this Circular Letter is to remind building control bodies of considerations relating to assessing compliance with requirement B4 of Schedule 1 to the Building Regulations 2010 with regard to fire spread over the external walls of a building and, in particular, the application of that requirement to low-rise buildings.

We are issuing this reminder because recent events have indicated that consideration is not routinely given to Requirement B4 and the need to resist the spread of fire over external walls in circumstances where the guidance in the approved document is not specific. As with all the functional requirements in Schedule 1, Building Control Bodies should use judgement to consider the overall intent of Requirement B4, not just comply with specific guidance.

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Scope of this Circular Letter

The guidance in this Circular Letter applies to buildings and building work in England.

This guidance is relevant to projects for which a full plans application is made, or initial notice submitted and for existing projects. Building control bodies may wish to reconfirm that satisfactory evidence has been submitted that the requirements of paragraph B4 of Schedule 1 are being met for existing projects.

Introduction

Requirement B4 of the Building Regulations 2010 requires that – “the external walls of the building shall adequately resist the spread of fire over the walls and from one building to another, having regard to the height, use and location of the building”. This requirement applies to buildings of any height.

Approved Document B provides guidance on potential ways to achieve compliance with this requirement Paragraph 12.1 of Approved Document B (Volume 2) says that – “The external wall of a building should not provide a medium for fire spread if that is likely to be a risk to health and safety”1.

There is further detailed guidance aimed at preventing fire spread over the walls for buildings 18m or more in height.

In December 2018 the ban on combustible construction materials in the external walls of certain high-rise buildings was introduced into the regulations2.

Consideration

Whilst the use of combustible materials within or attached to the external walls of buildings below 18m are not expressly prohibited, it is necessary to consider the risk from fire spread to health and safety in relation to buildings of any height.

The potential for fire spread and its impact on health and safety can be exacerbated by the way materials are arranged on the building, their combustibility and, for instance, their proximity to escape routes. The risk this presents to health and safety increases with the height of the building and the evacuation strategy, particularly where people sleep in the building. Consideration may also need to be given to any attachments which form part of the external envelope of the building.

Consideration should be given to ensuring that the overall intent of Requirement B4 is being met. 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

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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.

Enquiries

Telephone enquiries on this Circular Letter should be addressed to Technical Policy Division on 0303 444 0000 and all e-mail enquiries to enquiries.br@communities.gsi.gov.uk.

Yours faithfully

Frances Kirwan

Deputy Director

Technical Policy Division

Building Safety Portfolio