The World's Most Advanced Building

THE WORLD’S MOST ADVANCED BUILDING MATERIAL IS... WOOD AND IT’S GOING TO REMAKE THE SKYLINE By Clay Risen Posted February 6, 2014 Dan Bracaglia A Wooden Skyline On a cloudy day in early October, the architect Andrew Waugh circles the base of a nondescript apartment tower in Shoreditch, a neighborhood in East London. Shoreditch suffered heavily during the blitz of World War II—“urban renewal, compliments of the Luftwaffe,” Waugh says—and then spent decades in neglected decay. Recently, though, the neighborhood has come roaring back. Nightclubs and tech start-ups arrived first on the promise of cheap rent, and residents followed. Along with them came architects, urban planners, and engineers, many of whom make a pilgrimage to the same tower that Waugh now circumambulates. From the outside, there is nothing particularly flashy about the nine- story building, called Stadthaus, that Waugh designed with his partner, Anthony Thistleton. Its gray and white facade blends almost seamlessly into the overcast London skies. It’s what’s inside that makes Stadthaus stand out. Instead of steel and concrete, the floors, ceilings, elevator shafts, and stairwells are made entirely of wood. But not just any wood. The tower’s strength and mass rely on a highly engineered material called cross-laminated timber (CLT). The enormous panels are up to half a foot thick. They’re made by placing layers of parallel beams atop one another perpendicularly, then gluing them together to create material with steel-like strength. “This construction has more in common with precast concrete than traditional timber frame design,” Thistleton says. Many engineers like to call it “plywood on steroids.” When it opened in 2009, Stadthaus was by far the world’s tallest modern timber building. Since then, CLT towers have sprouted up everywhere. Waugh Thistleton built a seven-story apartment tower near Stadthaus in 2011, and construction is under way on a 90-foot-tall wood building in Prince George, British Columbia. In 2012, Stadthaus lost the height record to a 10-story apartment building in Melbourne called Forté. Wood is both renewable and a carbon sink. There are plans to go even higher. Swedish authorities have approved a 34-story wood tower in Stockholm, while Michael Green, a Vancouver architect, is seeking approval for a 30-story tower in his city. And the Chicago architecture mega-firm Skidmore, Owings & Merrill recently published a feasibility study for a 42-story tower made predominantly of CLT. It’s become a competition among architects to see who can build the next tallest wood high-rise, says Frank Lam, a professor of wood building design and construction at the University of British Columbia. Why the sudden interest in wood? Compared with steel or concrete, CLT, also known as mass timber, is cheaper, easier to assemble, and more fire resistant, thanks to the way wood chars. It’s also more sustainable. Wood is renewable like any crop, and it’s a carbon sink, sequestering the carbon dioxide it absorbed during growth even after it’s been turned into lumber. Waugh Thistleton estimates that the wood in Stadthaus stores 186 tons of carbon while the steel and concrete for a similar, conventionally built tower would have generated 137 tons of carbon dioxide during production. Wood nets a savings of 323 tons. Demographers predict that the planet’s urban citizenry will double in 36 years, increasing the demand for ever-taller structures in ever-denser cities. Whether architects and construction firms build those towers from unsustainable materials like steel and concrete or employ new materials like CLT could make a huge difference in the Earth’s health. Put differently, the world’s urban future may just lie in its oldest building material. KLH UK Cut & Assemble Cross-laminated timber (CLT) panels are cut to spec in a factory and assembled at the construction site. When most people think of wood architecture, they imagine a balloon— or, rather, a balloon frame, the lightweight but sturdy residential- building system of thin wood beams introduced during the mid–19th century (so light, people said, that it might just float away). The frames, also known as “Chicago construction,” for the city where they first became popular, are cheap and easy to build. But while they are strong enough for a few floors of residential construction, balloon frames buckle quickly under more weight. That became a problem in the late 19th century, as cities began to grow up as well as out. Fortunately, at around the same time, engineers and architects discovered how to use steel and concrete to build high-rise structures that could climb far above the tallest balloon frames. Chicago’s 138-foot Home Insurance Building, which opened in 1885, was the first to employ a steel skeleton, and thousands followed in quick succession. It didn’t help wood’s case that in the late-19th and early-20th centuries a series of horrible urban fires swept through square mile after square mile of wooden houses and apartment blocks in cities such as Baltimore, Chicago, and San Francisco. These disasters led to strict local construction codes that limited the height of residential wood buildings to as low as five floors. The rest is architectural history. The great forests of skyscrapers that grew across the world’s cities in the 20th century were made almost entirely of steel and concrete. “There was a long period where people forgot how to use wood,” says Alex de Rijke, a partner in the London architecture firm of dRMM, which has worked extensively with mass- timber design. But over the last two decades, architects and engineers have begun to rethink the possibilities of wood as a structural building material. First came the technology itself. In the mid-1990s, the Austrian government funded a joint industry-academic research program to develop new, stronger forms of “engineered” wood to soak up the country’s oversupply of timber. The result was CLT—a lightweight, extremely robust material that could be prefabricated and custom cut. The simple beauty of CLT is its orthotropic quality. Normal wood is strong in the direction of the grain but weak in the cross direction. CLT’s perpendicular layers make it strong in two directions. And because it relies on layers of smaller beams, it can reduce waste by using odd- shaped, knotty timber that lumber mills would otherwise reject. CLT came about just as architecture was going through its own technological revolution. In the past, an architect would draft schematics by hand and send them to an engineer, who would convert the documents into specifications for each wood beam or steel plate. The components would then be cut at a mill and assembled, piece by piece, on-site—an expensive, time-consuming and often imprecise process. Today, that’s all done by computer. An architect designs a building using 3-D AutoCAD software, and the program generates the material specs and sends them to robotic wood or steel routers, which shape panels with millimeter precision. The result is a set of building blocks that a small crew of workers can screw together in a matter of weeks. It took just 27 days for four men, working three days a week, to erect the timber portion of Stadthaus, about 30 percent faster than a comparable steel-and-concrete structure. Instead of building the tower from scratch on-site, Waugh said, it was more like assembling a piece of furniture. “The instructions are like Ikea but a little more straightforward, and the names are more pleasant,” he says. Courtesy SOM Redesign For all its benefits, CLT has been a tough sell until recently. After employing the material to build a small arts club in 2003, Waugh and Thistleton spent years trying—and failing—to convince more clients to use it. “Whatever client came in, timber came on the table,” says Waugh, “and after an hour, timber all too often came off.” The resistance arose from assumptions about wood as a material: Clients believed that any wood structure would behave like a balloon frame, with its structural weaknesses and vulnerability to fire. “We found the journey at times frustrating,” Thistleton says. “One thing we found was the inability of anyone to distinguish between mass timber and a timber frame.” Fire is, of course, the first concern that comes to mind with wood construction. And yet, mass timber is actually safer in a fire than steel. A thick plank of wood will char on the outside, sealing the wood inside from damage. Metal, on the other hand, begins to melt. “Steel, when it burns, it’s like spaghetti,” says B.J. Yeh, the technical services director for APA—the Engineered Wood Association. Slowly, though, developers are coming around, particularly those that grasp the economic benefits of building with CLT. When the Australian arm of Lend Lease, a global project management and construction company, began to design Forté, a 10-story apartment building in the docklands neighborhood of Melbourne, its engineers were not considering mass timber. “We originally looked for a lightweight construction solution that could work on relatively poor soil conditions,” says Andrew Nieland, who oversees timber construction projects for the company. CLT, they found, made the most sense financially. “We did our due diligence and came across engineered timber,” Neiland says. Generally speaking, CLT construction is about 15 percent cheaper than conventional steel and concrete, according to research by Waugh Thistleton. Tenants are getting on board too. Despite fears that some may be turned off by safety concerns surrounding life in a wood tower, Forté proved to be a huge commercial success, with all the units sold out.

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