Timber construction has come to a near-halt in the shadow of a deadly 2017 conflagration, even though the material played no role in it.
(Bloomberg) — This article is part of the Bloomberg Green series Timber Town , which looks at the global rise of timber as a low-carbon building material.
To get fire department approval for their six-story London office project made of strong engineered wood known as mass timber, Theo Michell and Richard Walker had to build a full-scale section of it in the UK, ship it to Poland and attempt to set it on fire.
The mockup was set alight “with enough material that replicates the fire load that you get from furniture and carpets and desks, and all the rest of it, and you see how that structure performs,” says Michell.
“It was cool,” adds Walker. “It looked amazing.”
Their building, called Paradise, passed the fire test and is under construction, though not without a significant drag on their budget and time.
Designed with hopes of a negative carbon footprint, the building is a first foray into timber for Michell, chief operating officer of Bywater Properties, and Walker, the company’s chairman, who is also the executive chairman of the British supermarket Iceland Foods, the family business started by his father. Bywater, which just announced a partnership with Japanese forestry and housing company Sumitomo Forestry to develop modern timber buildings in Europe, has found itself at the vanguard of efforts to push large-scale timber building in the UK.
Neighboring France and the city of Amsterdam, mindful of the carbon impact of concrete and steel, now have mandates for minimum percentages of timber in new buildings. By contrast, the UK has banned combustible materials, including timber, in the structure and facades of residential buildings over 18 meters (59 feet).
Amid fear, confusion and distrust, the push for mass timber in apartment buildings, hotels and hospitals has ground to a halt, insurance brokers, architects and engineers told Bloomberg Green, threatening efforts to tackle carbon emissions from the building sector.
The reason? A tragedy that had little to do with timber itself, but everything to do with Britain’s troubled construction industry.
Race to the bottom
In June 2017, in west London, 72 people died in an apartment-tower fire that should not have killed anyone. It should not, in fact, have spread beyond the home where it originally started, caused most likely by a faulty fridge-freezer. Residents of the other apartments in Grenfell Tower were told to stay put, which according to the building’s design should have kept them safe. But instead, as firefighters tackled the blaze inside one kitchen, the cladding (or layer of material) on the outside of the building caught fire, spreading the flames to other homes.
An inquiry, which is still ongoing, has suggested failures by almost everyone involved: the local council, the government, the builders, the suppliers and manufacturers of the cladding. Judith Hackitt, an expert in building safety commissioned to investigate after the disaster, concluded in 2018 that there was a “cultural issue across the sector, which can be described as a ‘race to the bottom’ caused either through ignorance, indifference, or because the system does not facilitate good practice.”
The fire had nothing to do with timber. The cladding on the tower, which quickly spread the flames from floor to floor when they were supposed to be confined to one flat, was made from an aluminum composite material with a plastic layer. Earlier tests should have raised concerns that the material was not fire-safe.
But timber, in both structures and cladding, has been swept up in regulations brought in by the UK government and local governments in response.
As well as the national ban over 18 meters, the Greater London Authority, the body that governs London, introduced an even stricter ban for developers hoping to qualify for affordable housing funding. It banned combustible materials entirely from external walls in buildings of any height, prompting several large housing associations to abandon mass timber as a material.
A UK government spokesperson said in a statement, “There are many potential benefits to using timber in construction and we have committed to increasing its use as part of our Net Zero Strategy, guided by fire safety considerations.” The spokesperson added, “We are working with industry to develop further opportunities for its use through a cross-government working group.”
From the series: How a Seattle Architect Helped Make Timber Towers Legal in the US
The problem isn’t necessarily that the UK is too risk-averse, says Jose Torero, a world-renowned fire safety expert and senior civil engineering professor at University College London. It’s that a confusing patchwork of international regulations around timber building and lack of competence has left the UK, post-Grenfell, afraid to act.
“The only difference between the UK and the rest of the world is that the UK is more sensitized because of Grenfell. They are more nervous; they cannot be convinced of what is right and what is wrong,” Torero says.
Timber is flammable, of course. Hackitt’s report also cites another apartment-block fire in which the flames spread between floors via wooden balconies. A series of high-profile fires in timber-framed buildings under construction in London in the early 2000s also showed the potential for timber to catch alight unexpectedly and catastrophically.
But there is a difference between these older timber-framed buildings and the modern materials used to construct Paradise and other cutting-edge mass timber buildings.
The most common of these materials, cross-laminated timber or CLT, is formed of panels made from layers of lumber stacked and glued together, then compressed. It’s stronger than concrete and steel on a pound-for-pound basis and has outperformed both materials in fire tests in the US and Europe, where it has been used in major building projects, including high-rises.
Black and white
One rare new UK example is the Black and White Building, in east London, which isn’t black and white at all but a soft wood-brown, both inside and out. There is no ban on timber in office buildings like this one or in schools, but they are still difficult to build now. A lot of the problem is perception, says David Lomax, an associate director at the firm Waugh Thistleton Architects.
Clients tend to be risk-averse. “The biggest challenge is the loss of confidence,” he says. “There’s a lot of nuance, but people who are making really big decisions about really big budgets see a message that says timber has been banned.”
In many cases, clients come forward with enthusiasm for timber but abandon it for concrete or steel once they’ve investigated the costs and complications involved, says Louisa Bowles, partner and head of sustainability at the architecture firm HawkinsBrown. Her practice last designed a partial mass timber building in around 2015, a science and research building for the University of Warwick.
“Whenever we suggest it now, it’s always received warmly but very rapidly discarded as an option,” she says. “Definitely in our experience, at the scale of work we do and the type of clients we’re working with, there’s a very risk-averse attitude, especially in the wake of Grenfell.”
Insurance doubt
A big part of the problem is that it’s become more difficult to get insured. Insurance is cyclical: It goes through stages of being cheap and easy to get, and stages of being difficult and costly. A series of disasters including Grenfell, Covid-19 and wider inflation has pushed prices up across the industry and reduced appetite for risk. At the same time, Grenfell opened insurers’ eyes to some of the worst excesses of the construction industry.
“There’s been a real breakdown of trust between the insurance industry and the building industry post-Grenfell, that we are now five years on in the process of rebuilding,” says Dominic Lion, who specializes in mass timber building at the insurance broker Gallagher. “We placed the construction insurance for the Black and White building pre-Grenfell, and if I’m totally honest it wasn’t that difficult, or that expensive. If we were to do it today it would be a lot more difficult and a lot more expensive.”
Professional indemnity insurance for fire engineers, who advise on building design, has become much more expensive, and they are busy reassessing thousands of British buildings affected by the cladding scandal that arose after Grenfell — so they are less inclined to take a risk on something new.
“We really need the fire engineers to tell a story to the fire brigade, who don’t have the in-house expertise to do that; they rely on consultants,” says Kelly Harrison, associate director at engineering company Whitby Wood and an expert in timber design. “Often it’s the fire brigade which stops things going ahead … Then obviously there’s insurance as well. If we get through all those hurdles, then the insurers don’t have the expertise.”
As Michell and Walker found, doing a new type of building for the first time is an expensive and frustrating endeavor, though it will be easier for those who come after them.
“I’ve literally spoken to people in government who’ve told me that if a fire test happens in another country, it’s not valid,” says Andrew Waugh, of Waugh Thistleton architects, the firm behind the Black and White building. “There’s a lot of that going on, this kind of backwards movement, which has been incredibly frustrating because this is a technology that was innovated in the UK. We built the first tall building in the world here, in timber, in 2008,” he says, gesturing to a miniature model of a block of flats, Murray Grove in Hackney, beside the table where we are sitting at Waugh Thistleton’s office in east London.
At almost 30 meters (98 feet) tall, Murray Grove would be impossible to build now. “It’s really disappointing,” Waugh says.
In response, the industry has spent £500,000 on its own fire tests over the past several years, and is planning to release the full results in an accessible format around the end of the summer, in the hopes of creating a UK fire-resistance standard for CLT. It recognizes that it’s also fighting generations of received wisdom.
“The minute you talk about timber, the first thing people say is, ‘Well, it burns,’” says Andrew Carpenter, chief executive of industry group the Structural Timber Association, which coordinated the tests. “Well, yes — but it’s the way you design and construct it. If you go to the mass timber situation it actually performs in fire probably better than any other material, because it chars. But that’s something you’ve got to prove with these fire tests.”
Taking the plunge
Better, early communication between construction teams and insurers would help improve confidence, says Philip Callow, an experienced underwriter and broker who is now creating a “playbook” for mass timber project teams seeking insurance.
Timber-specific building codes would also help, he says. “We can’t simply take someone else’s regulation — we have to check it, sense-check it, peer review it. But there are other jurisdictions that are doing it. The same insurance companies are doing it [elsewhere] that are not doing it here,” he says.
Another effort, the New Model Building, led by Waugh Thistleton, Torero and others, aims to create a design template for a six-story mass timber residential building that would come with fire safety reports, carbon data and a “letter of comfort” from a warranty provider. The idea is to replace doubt and fear with the certainty and confidence that has disappeared since 2017, as well as to make sure a timber building boom doesn’t end up repeating a Grenfell-style tragedy.
In the longer term, climate imperatives will be powerful. Britain has pledged to reach net zero by 2050 and the built environment makes up roughly a quarter of its carbon emissions. The government is considering introducing legislation that would set limits on emissions from building projects and provide a strong incentive for lower-carbon materials like timber; it says a consultation will be launched this year.
Laws tightening building regulations might actually help create confidence, especially with a proposed new rule requiring an “accountable person” to make sure a residential building is safe. Mass timber building should — in theory — be more easily monitored than conventional steel or concrete construction because of the way it’s fabricated largely off-site, then assembled with pieces that are numbered and trackable using QR codes, much like an Ikea bookshelf.
The insurance market has powerful ESG incentives to find a way to support lower-carbon building, as do investors. Michell of Bywater Properties, developing the Paradise building, is optimistic. “It takes a player like us, who is relatively small but entrepreneurial in mindset, to say: ‘We see the merit in doing this. We’re going to take the plunge.’”
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