Architects have voiced concerns that proposed changes to Approved Document B (ADB) guidance could block the use of timber in high-rise buildings and be “extremely detrimental for the decarbonisation of the construction industry”
The opinions, compiled and shared in an article by the Architect’s Journal (AJ), emerged following a new consultation from the Health and Safety Executive (HSE) to review the current statutory guidance for fire safety in buildings.
Among other changes, the consultation seeks to revise and update guidance on external wall systems and balconies and review the scope of the ban on combustible materials in and on external walls. A threshold system will also be introduced, whereby the guidance within Approved Document B should not be applied when combustible elements of structure are used. As the consultation notes, while ADB guidance supports the use of timber structures in low-rise buildings, the Building Safety Regulator (BSR) has stated that some parts of the guidance do not apply to high-rise timber buildings, specifically “tall, large or complex buildings with combustible elements of structure”.
“To clarify what BSR considers as ‘tall, large or complex’ when combustible elements of structure are utilised, we are seeking to introduce a clear threshold within the guidance. The threshold will make clear the height above which buildings utilising combustible structural elements (including timber) cannot solely apply the guidance within Approved Document B to demonstrate compliance. Where combustible structural elements are used, an alternative approach is expected.”
The revised version states: “In buildings with a storey more than 11m above ground level, loadbearing elements of structure should be constructed using materials or products achieving a minimum classification of A2-s3, d2 or better.”
Here, class A2 refers to “very limited combustibility”, with some industry stakeholders arguing that the majority of timber products would not be able to meet this standard. For other building heights, the guidance suggests that any loadbearing elements of structure that do not achieve class A2s3, d2 “should not be exposed”. However, this provision does not apply to buildings with occupied storeys up to 4.5m above ground level and in single-storey industrial buildings.
Joe Giddings, European networks lead at the non-profit Built by Nature, told AJ that the changes could have a significant impact on the drive towards more sustainable builds and that it would be a “massive setback for climate mitigation”.
“As we all know, timber is one of the most effective tools in the box when it comes to reducing embodied carbon emissions from new buildings, and with the right approach, fire safety can be achieved even in very tall timber buildings,” Giddings said.
Whitby Wood director, Kelly Harrison, said: “The proposed update could be extremely detrimental for the decarbonisation of the construction industry.
“Securing approval from multiple regulatory bodies (many of which may lack expertise in this area) for solutions outside the approved documents will be both time-consuming and costly for project teams, with an added element of design programme risk that a lot of clients can’t make viable.”
Lucy Picardo, director at Haworth Tompkins, added: “We support the government’s commitment to improving fire safety and reviewing Approved Document B. However, the proposed changes would deal a significant blow to the construction industry’s efforts to decarbonise.
“At a time of climate crisis, the UK should be developing clearer guidance on what measures can support safe timber use; otherwise, the UK risks falling even further behind Europe and other international peers in progressing low-carbon construction.”
You can read the full piece from AJ here.
The consultation proposal on changes to Approved Document B: Fire Safety is open until 1 July 2026. More details can be found here.
Part-supported by funding from Built by Nature, the Alliance for Sustainable Building Products (ASBP) has produced a Mass Timber Insurance Playbook. This publication was written by insurance and building resilience specialists, to help stakeholders in the insurance and construction industries understand each other’s priorities and language when it comes to the use of mass timber in buildings.
The aim is to enable a collaborative approach between construction teams and insurers, opening the door to more equitable insurance for mass timber buildings. The playbook is available here.