Proposed changes to Approved Document B could threaten timber construction and make achieving net zero harder in England

The government’s Timber in Construction Roadmap, which sets out timber as an innovative method of constructing low-carbon, high-quality, affordable homes, was well-received by the built environment.

 

Now, changes to Approved Document B could halt the use of timber entirely in buildings over two storeys, undermining the Roadmap and the UK’s net-zero targets.

 

"Timber will be a central material in any credible route to net zero, yet the key growth sectors for mass timber, such as mid rise housing, student accommodation and mixed use schemes, are pushed to the margins or ruled out altogether if projects are forced to follow only the most restrictive, standard guidance routes," says Mellis Haward, Director, Archio Ltd. 

 

Consultation closes next week (1 July) on the changes, first published in March 2026, that could limit the use of timber in structures over 11m in height.

 

This would significantly change current compliance that sets out combustible material as unsuitable for buildings 18m or higher in load-bearing elements or in external construction. 

 

The new threshold still allows for timber use above 11m should a fully fire-engineered approach be taken – but experts fear the cost and programme delays of fire engineering will lead to an avoidance of timber.

 

Industry figures are urging professionals to respond to the consultation.

 

Matthew Duckett, Associate Sturctural Engineer at BuroHappold believes the government does not have the evidence to support its proposal. "There’s no published risk analysis showing why 11m becomes more dangerous, and no operational change in evacuation of fire-service response at that height," he writes on LinkedIn. 

 

"Dropping the threshold to 11m isn’t evidence-led – it’s a regulatory downgrade that expands the ’higher-risk’ category... The impacts will be significant: [It will] deter timber specification and restrict mainstream timber use in exactly the building types where it delivers the biggest embodied‑carbon savings."

 

Although the guidance is only advisory, the ADB is often used as the de-facto standard in planning and regulatory standards.

 

Since restrictions on combustible materials were introduced in 2022, timber has already become a less commonly-used material. There are fears this change will lead to timber becoming an increasingly expensive and scrutinised construction material, affordable only to a small subset of schemes.

 

Haward says that: "There is clear international evidence that taller timber buildings can achieve high levels of fire safety when supported by rigorous, performance based fire engineering, so the regulatory direction in the UK should focus on tested performance outcomes, not broad brush prohibitions on combustible materials.

 

Find out more Respond to the consultation proposal on changes to Approved Document B