Review of Approved Document B: Fire Safety

62. The Grenfell Tower Inquiry Phase 2 report made clear that the guidance for resisting fire spread over external walls in section 10 of Volume 1 and section 12 of Volume 2 of Approved Document B should be reviewed as a priority.  

63. Since 2017, sections of Approved Document B providing external wall guidance have undergone several technical changes. These include:  

1. Introducing the ban of combustible materials in and on external walls above 18m in relevant buildings in 2018  

2. Clarification of Approved Document B in 2019 

3. Addition of new section on balconies   

4. Introducing new guidance for residential buildings between 11m and 18m in height 

64. The technical review of Approved Document B included a research workstream on the classification of external wall systems. Although this research is not yet finished, the work undertaken so far has informed this new draft guidance. The objective of the redraft is to provide clear and comprehensive guidance on external fire spread and go further in some places.  

65. Through the 2022 sprinklers in care homes, removal of national classes, and staircases in residential buildings consultation, we undertook a call for evidence on paragraphs 10.6, 10.7 of Approved Document B 2019 edition. We have also proposed changes expanding the current guidance to respond to the evidence provided through the call for evidence.  

66. The new guidance established recommendations for all buildings of any height. We have also extended the guidance to the whole external wall system to remove any doubt about its scope and application. This includes advice on the performance of the backing layer, insulation, and the external product (to also cover composite products). Any deemed-to-satisfy provisions are proposed to be removed, and their remit will be replaced with performance classifications. 

67. Through updating this section of the guidance, we aim to clarify:  

1. that fire spread over roofs and external fire spread via balconies comes under requirement B4 in the intent section  

2. the section’s height thresholds and measurements align to those with the rest of the document and Appendix D, and clarify the provisions for single storey buildings  

3. the separation of envelopment hazards (spread over the wall of the building) and the exposure hazards (building to building fire spread)  

68. The ban on combustible materials in and on external walls and specified attachments is prohibiting the use of laminated glass products as balustrades. The sector, through the 2018 call for evidence, raised this as a topic to be investigated and further explored.  

69. Research underpinning the continuous review of Approved Document B investigated the matter in detail, which involved extensive laboratory and large-scale experiments. Based on the findings of our research, we are amending  the current guidance on balconies in all buildings and consulting on further changes to the building regulations. This will involve proposing recommendations in the guidance and an exemption to the ban correspondingly to allow the use of laminated glass balustrades of certain dimensions and characteristics. 

70. The changes to the guidance better support the balance of proportionate provisions and will clarify the relevant performance standards for components of the external walls and balconies and where the provisions apply.  

71. Regulation 2(6) provides the definitions for the relevant terms for the ban of combustibles in or on external walls and specified attachments. Regulation 7(3) provides a list of exemptions to the ban. The following text is proposed, following the findings of the research, as a definition for laminated glass products to be included in regulation 2(6) so that they become exempt under Regulation 7(3):

Laminated glass products are defined (in regulation 2(6)(X)) as any panel or sheet, having a total thickness of more than 17.5mm but no more than 26mm which is composed of two or more layers of glass, and one or more layers of interlayer material which is a substantial layer made of a material having a gross calorific value of no more than 41MJ/kg when tested in accordance with BS EN ISO 1716 and a thickness less than 1.6mm. A substantial layer is defined as a layer which is at least 1mm thick or has a mass per unit area of at least 1kg/m².

72. Any changes to regulation 2(6) and 7(3) will require a statutory instrument to implement.  

73. The changes proposed to section 10 of Volume 1 and section 12 of Volume 2 of Approved Document B impact all building types covered by the guidance. For all building types above 18m, we do not anticipate any impact.  

74. Through our review of industry practices, we have identified that the majority of the sectors impacted are already working in line with the updated guidance. This has reduced the potential impact of the changes to only those who are outliers.  

75. Our assessment of the overall impact of the changes are estimated to provide a total present cost of £35 million over 10 years, with an equivalent annual net direct cost to business (EANDCB) of around £4.1 million. 

76. The highest cost of the policy will be to residential buildings under 11m accounting for 67% of the policy cost. This is due to the number of buildings impacted, with the cost per building estimated an average of £1,335 and impacting less than 1% of residential buildings below 11m.   

77. The costs of meeting the improved fire classifications outlined within the guidance are focused on:  

1. substrates 

2. external covering products 

3. balcony construction 

78. The proposed exemption to the ban on combustible materials in and on external walls for laminated glass to be used in certain situations is not expected to have a cost associated with it. It will however increase the choice of products available for use by industry and therefore will be provide some benefits.  

79. All estimates are in 2025 prices and 2027 present values. The policy implementation period is 2027 to 2036. The costs and benefits of the policy are appraised over the lifetime of the building elements that are impacted by the changes.