Is the future of the city made of wood?
Moments after entering his practice’s latest site, the Black and White office block in Shoreditch, architect Andrew Waugh rushed to stroke the planks – a mix of honey-coloured European softwoods – that form the interior walls. He then touts window louvers made of dark, baked American tulipwood, usually used to make cardboard pallets. Waugh, it quickly becomes clear, has a thing for wood.
He orders me to take a deep breath. Instead of the usual construction site smells of damp concrete and damp plaster, there is a pleasant scent of fresh wood. I’m not entirely convinced that I’m lost in a forest, but I’m not far from it. Meanwhile, Waugh’s eyes sparkle with excitement. “It will change with each season, depending on temperature and humidity,” he says of the fragrance. “Every spring, every fall, you get a little reminder of the composition of the building.”
From the outside, the building looks modest. It’s a five-story glass box shaded by those dark vertical louvers, with a bright lobby and generous, open-plan workspaces on the upper floors. But his skeleton is revolutionary. Where you would expect to find steel, concrete, and masonry, the columns and beams are constructed from some kind of plywood (laminated veneer lumber, or LVL, made primarily of European beech central), with European softwood floor tiles (CLT or cross-laminated timber, thin planks glued in the direction of the grain for added strength). Another type of engineered wood called glulam (an amalgam of “glued laminated” wood) is used for curtain walls. Everywhere you look there is wood. And, when it opens later this year, the Black and White will be central London’s tallest timber office development.
According to Waugh, whose practice Waugh Thistleton has become one of Britain’s leading timber specialists, it weighs only a fifth of a conventional building of its type. “There’s less than a ton of steel in all this,” he says. What’s holding him back? He smiles: “13,000 vis.”
Joining planks of wood can be an extremely old way of building; the oldest surviving wooden structure is a Japanese temple dating to AD607. But it’s also one of the hottest things in architecture right now. Sometimes called the “concrete of the future”, CLT and other engineered woods are redefining the world of design, displacing construction methods that have dominated since the first reinforced concrete buildings began springing up in the world. dawn of the 20th century. .
Last month, a 25-story, 86.6m building in Milwaukee was certified as the world’s tallest log tower, replacing the 18-story CLT skyscraper in Norway that broke the record in 2019. log buildings – apartment buildings, offices, school buildings, sports halls – are planned everywhere from Adelaide to Toronto.
According to devotees, the reasons are clear. The wood is not only sustainable, if forestry is managed properly (Waugh Thistleton estimates that the 1,330 cubic meters of wood used for the Black and White took just 137 minutes to grow.) It also stores rather than spend CO₂. Buildings and the construction industry are responsible for 39% of global carbon emissions (aviation, on the other hand, accounts for just 2.1%) according to a 2017 UN Global Status Report. . So that potentially changes the game.
Climate-conscious architects see wood as integral to achieving the goals of the Architects Declare movement, which calls on designers and clients to monitor the “embodied carbon” used to create buildings, drastically reduce emissions, use better insulation and better heating, and much, much Suite. “Everyone has an understanding of climate now,” says Waugh’s colleague, associate architect Jennifer Monaghan. “And wood is one of the most sustainable building materials there is.”
She adds that it is also much easier to work with. When a client from another recent office project in east London decided at the last minute to add a staircase, the builders simply used a circular saw to cut through the affected floor tiles and the insert. “It took two days,” she says. “A bit unbelievable.
“The wood just clicks together,” Waugh explains as we ascend an all-wood staircase through an all-wood core at Black and White, explaining that each piece of wood is made offsite, then given a unique QR code. which allows the contractors to set it up like Lego. “If this building had been concrete, we would have had cement mixers lining the streets for months.”
What about the cost? I ask Charlie Green of workspace pioneers The Office Group, who commissioned the Black and White. He joins us for the tour. “There’s a 10-15% premium,” he says. “But you get it back in other ways: the volume of deliveries is something like a tenth of a traditional construction site.”
I’m starting to think there aren’t many downsides until Green guides us to a rooftop terrace facing the city, with the needle-punched spiers of the Wren churches dwarfed by huge slabs of glass and of steel. It is impossible to forget that these churches were erected after the great fire of 1666 which reduced much of central London to smoking rubble, one of many conflagrations of the past 500 years which make the dangers of wood construction. One of the first things authorities in London did after this disaster was to insist that buildings be clad in brick and stone, measures that were later replicated in cities around the world.
While a handful of projects in the UK have grabbed the headlines – another practice named DRMM has built well-regarded CLT apartment buildings at Elephant and Castle and a CLT sports hall at King’s Cross by Bennetts Associates which has opened last January to applause – developers and architects here have been reluctant to embrace a material still seen as experimental, even risky. The contrast with the enthusiasm observed in other countries is striking.
One obvious reason is the shadow cast by the Grenfell Tower fire five years ago. While it was the aluminum-polyethylene cladding, not the wood, that made this fire so catastrophic, critics say it illustrates the dangers of involving flammable materials in high-rise construction. In 2018 the government banned the use of combustible materials (including CLT) in the exterior facades of buildings over 18m high in England, and although the rules were changed in June, the Mayor of London , Sadiq Khan, has pushed for even stricter regulations.
The mayor’s office tells me that while Khan is a proponent of sustainability, safety remains a concern. “Sadiq is helping the industry further test the safety of CLT and other wood products to see if they can be used on exterior walls without risk,” a spokesperson said. But a new London-based fire safety plan is currently in consultation and appears to have a low opinion of wood.
Does it really make sense to build massive all-wood structures in dense urban centers, I ask Waugh, especially when summer temperatures now regularly exceed 40°C in many parts of the world and wildfires have become frighteningly familiar, even in the UK?
He insists that the risks are exaggerated. Large blocks of wood char rather than burn. “If you put a log on a fire at night, when you wake up in the morning, it will still be there. Charring protects it. If you see these devastating images of large forest fires, all the trees are still standing because they are charred.
Others are much less optimistic. When I talk to Rory Hadden, a lecturer in fire investigation at the University of Edinburgh, he points out that “charring always burns: wood is a combustible material”. Steel and concrete also have their weaknesses during fires, Hadden adds. No structure is indestructible and securing a building depends on many factors. “But the problem is that we don’t really know how these engineered wood products burn. A solid piece of wood is one thing, but a material like CLT, made up of different layers glued together, supports all these loads? We don’t understand enough yet.
Context is everything, Hadden says. “Do I want to make it a 20-storey skyscraper in central London? Well, I have some concerns. But if I want to build a low-rise community center somewhere in CLT, I think that’s a great idea.
So he wouldn’t want to work in a hardwood office building? He’s laughing. “I’ll give you the same answer I give to architects who ask me that: I just don’t know.”
Other countries are racing ahead. Deeply forested Germany and Austria produce around 80% of the CLT used worldwide. The Nordic countries were pioneers. In the United States, New York, Utah and Idaho recently updated building codes to approve solid wood. In France, the government of Emmanuel Macron has required that all new public buildings contain 50% wood or other bio-based “organic materials”, such as cork or mycelium, a high-tech material derived from fungi. “But mushrooms aren’t going to solve the housing crisis,” Waugh says, pointedly.
Whatever happens in the UK, says Green, the era of offices and other buildings being built without considering their impact on the climate is over. Apart from anything else, the people who work there are more demanding than ever. “That building model where you don’t consider the carbon, where you don’t think about the health and well-being of the people inside?” he says. “It’s not our future.”
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