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Mass timber buildings could face height restrictions in U.K. over Grenfell fears

Chopping Down Tall Wood

Mass timber buildings could face height restrictions in U.K. over Grenfell fears

A wood-framed apartment building under construction in Manchester, England, in 2009. (Pete Birkinshaw/Flickr)

Government officials in England are poised to take an ax to the tall timber trend by moving to lop the maximum height of wood-framed residential buildings and hotels from six stories to just three or four.

The potential restrictions arose as part of a just-concluded consultation process on the use of certain external cladding materials in new construction in England and Wales with a focus on flammability—an urgent concern in the wake of 2017’s deadly Grenfell Tower fire.

To be clear, the Grenfell Tower was a concrete slab structure—as was the norm for London housing blocks in the early 1970s when the 24-story structure was completed—and the primary cause of fire’s spread was found to be aluminum composite cladding panels. Due to the use of specialized wood flame retardants and fireproof cladding materials, modern timber structures, no matter their height, are not viewed as particularly more susceptible to fire than non-timber buildings. Still, with Grenfell tragedy still fresh in the minds of many Londoners there’s a view that even slightly tall-ish buildings—in this case, anything over 36 feet—built from structural timber could present an elevated fire safety risk even if a building’s external walls are not wood. (The restrictions would apply to wood cladding and structural timber.) Per legislation floated by the government, any structures over 36 feet would be limited to having wood floors.

As reported by BBC News, the decision has received swift pushback from the timber building industry, which has already experienced a sharp decline in England following the Grenfell fire. Meanwhile, mass timber towers continue to stretch higher and higher in other European countries, particularly in Scandinavia. Tall timber projects are continuing to reach new heights in North America as well.

“Obviously no-one wants to see another tragedy like Grenfell; protecting life is the main concern. “But the government is over-reacting. Properly-constructed timber buildings can be safe in a fire – it depends on the design,” explained Matt Linegar of Finnish industry leader Stora Enso, to the BBC. “Even with the current guidelines introduced after Grenfell there has been a chilling effect on the industry. People commissioning buildings think ‘I’d better not use timber.’ The market has virtually dried up.”

In a lengthy statement, the Timber Trade Association argued that further limiting the height of residential timber buildings could have a detrimental impact on housing construction:

“The best way to improve this legislation would be to focus any extension of a ban on combustible materials down to 11 metres on the external cladding, not the structural wall itself. Making such a change to the ban would also bring us into line with regulations in Scotland, which banned combustible cladding above 11 metres, but does not include the structural wall in the scope of the ban.”

“One of the concerns which emerged from the Grenfell Tower fire was how quickly flames were able to spread across the surface of the building. This occurred due to the external combustible cladding and was not related to the structural walls. There is no evidence that structural walls pose the same fire risk as the external cladding, and so there is no justification for treating the two in the same way.”

The concrete industry, however, is requesting that no exceptions be made, including for mass timber. “Public safety is critical, and if further testing is required of materials like cross-laminated timber there is already too much doubt about its ability to protect people,” said Chris Leese, director of UK Concrete, in a statement.

Mass timber structures are viewed as an attractive, highly sustainable alternative to environmentally taxing concrete and steel construction. Most notably, wood buildings act as carbon sinks by locking in vast amounts of greenhouse gas.

Per statistics published as part of a study by Germany’s Potsdam Institute for Climate Impact Research (PIK) and shared by the BBC, a single five-story building built from cross-laminated timber (CLT) products can store nearly 400 pounds of carbon per roughly every 3 square feet. In the U.K., constructing a massive number of timber homes constructed from is seen as a way to both put a dent in the affordable housing crisis and reach legally-binding climate targets.

“There’s no safer way of storing carbon I can think of,” said  Hans Joachim Schellnhuber, director emeritus of PIK and co-author of the aforementioned study. “Societies have made good use of wood for buildings for many centuries, yet now the challenge of climate stabilization calls for a very serious upscaling. If we engineer the wood into modern building materials and smartly manage harvest and construction, we humans can build ourselves a safe home on Earth.”

Responses to the just-wrapped up consultation process will now undergo review before any final formal rules are instituted.