Britain’s building safety regulator is consulting on guidance that would ban structural timber in English buildings taller than 11 metres — roughly three to four storeys. That is according to a consultation on Approved Document B (ADB) opened by the Health and Safety Executive on 25 March, which closes on 17 June and applies to buildings across England.
Wood Central understands that ADB is England’s primary statutory guidance for fire safety compliance under the Building Regulations 2010. Architects say the proposal moves England in precisely the opposite direction to every other major construction market on earth.
Any building above 11 metres would need structural and cladding elements meeting an A2-s3, d2 combustibility classification — a bar most timber products cannot clear. Even specially treated engineered wood rarely achieves better than a B rating, whereas most cross-laminated timber and glulam products carry a D classification.
Post-Grenfell guidance already restricts combustible cladding in residential buildings above 18 metres — but the new proposal drops that threshold by seven metres and extends it to structural timber across every building type. Architects say nothing in the Grenfell inquiry findings justified a change of that scale.
Dropping that floor by seven metres and broadening the restriction to load-bearing structures across all building types, the proposal would target mass timber precisely at the height where it is most commercially viable. Architects say the industry has never faced a more counterproductive regulatory signal.
Andrew Waugh, whose practice, Waugh Thistleton Architects, designed the Black and White Building in Shoreditch — already above the proposed threshold — called the proposal “frankly, deeply frustrating and flawed.” He told the Architects’ Journal that “at a moment when almost every other country is updating its building codes to actively promote the use of timber, England risks becoming an outlier once again.”
Waugh said his practice was coordinating an industry-wide response, including alternative proposals he described as “both genuinely safe and fit for a low-carbon future.” That response is already taking shape outside the formal process.
Meanwhile Joe Giddings, European networks lead at non-profit Built by Nature, raised the alarm publicly on 28 March — “I cannot believe I am saying this again. Six years on from a very similar move.” He told the Architects’ Journal the proposal would be “a massive setback for climate mitigation,” placing the UK in direct contrast to the rest of Europe, where mass timber has become mainstream even in high-rise buildings.
Giddings urged the industry to respond before the June deadline, pointing to the Black and White Building itself as an example of sustainable architecture that would struggle to gain approval under the new guidance. Commercial consequences concern engineers as much as the policy direction.
Kelly Harrison, director at engineer Whitby Wood, warned the proposed update “could be extremely detrimental for the decarbonisation of the construction industry.” She said teams seeking approval outside the approved documents would face costs, delays, and design programme risk “that a lot of clients can’t make viable.”
Harrison argued the guidance should instead make low-carbon timber innovation more attractive to developers, calling it “one of the few viable ways to meet our 2050 targets using technologies that are already available at scale.” Architects across the sector share that concern.
Lucy Picardo, director at Haworth Tompkins, said her practice’s recent projects — Backstage at the Old Vic in London and an extension to Theatr Clwyd in Wales, both above 11 metres — proved timber performs “safely and effectively when combined with robust fire strategy and careful design.” She warned the UK risked “falling even further behind Europe and other international peers” if the proposals went through unchanged.
Not every reading of the consultation treats it as a hard stop.
Mars Fire Engineering director Louis Chaumont noted ADB only covers “common building situations,” and that performance-based design routes remain open for projects outside its strict letter. Engineers acknowledge, however, that the pathway adds cost, time, and unpredictability that most clients reject at the feasibility stage.
Where Chaumont sees a workaround, Geoff Wilkinson sees a deeper problem. Writing in the Architects’ Journal’s Building Regulations Column, Wilkinson pointed to the sector’s failure to produce fire-test data to support any alternative compliance argument.
Fire tests show CLT can delaminate under fire conditions, Wilkinson warned, adding fuel load and extending burn time well beyond the predictable charring behaviour of large-section solid timber. The Building Safety Regulator has shown it will lean hard on that distinction.
Vertical extensions face particular exposure — a seven-storey CLT structure built atop a 1950s London concrete frame saved more than 4,500 tonnes of embodied carbon and grew the building’s floor area by 40 per cent. Under the proposed guidance, that typology would need an alternative compliance pathway wherever the new roof level clears 11 metres.
Christian Dimbleby, UK head of sustainability at White Arkitekter, pointed to Sweden’s 75-metre, 20-storey Sara Cultural Centre in Skellefteå — a CLT hotel completed in 2021 — as proof that the gap between England’s proposed position and international practice runs deep. Dimbleby said the government “needs to think carefully about the environmental consequences” before bringing the proposal into effect, and the data backs him — mass timber assemblies passed the world’s first three-hour fire-resistance test for high-rise structures at the Southwest Research Institute in San Antonio, meeting a standard steel and concrete typically hold alone.
