In 2009, construction was completed on the Stadthaus, a nine-story, 29-apartment building in the rapidly gentrifying Shoreditch neighborhood of London. From a distance, the structure would have seemed to be a rather unremarkable postmodern addition to the neighborhood. Defin 2009, construction was completed on the Stadthaus, a nine-story, 29-apartment building in the rapidly gentrifying Shoreditch neighborhood of London. From nitively rectangular and rendered in pixelated shades of grey, the building would make for an entirely convincing urban dorm building.
Today, looking at Stadthaus, one wouldn’t imagine it was a prize-winning building, let alone an influential one. However, to understand its importance one must know the secret hidden within the building’s walls. Because from its frame to its elevator shafts to its exterior paneling, Stadthaus is built almost entirely of wood.
Long regarded as a limited and dangerous [historic city-wide fires tend to have a pretty awful effect on your reputation] material, wood may be making a major comeback. Thanks to a confluence of technological advances and ecological concerns, wood is developing a buzz as a kind of 21st-century wonder material. This shift in thinking is thanks, in part, to the success of the unassuming, grey Stadthaus building.
Designed by Waugh Thistleton Architects in London, the building is as much of a marvel of manufacturing as it is of design. The material used in the project, cross-laminated timber—or CLT—is a far cry from conventional lumber. With much of the world’s stock of old-growth lumber logged centuries ago, building massive projects with wood requires some technological enhancement.
Developed by KLH of Austria [a lumber-rich country no doubt thrilled to see wood make a comeback], CLT [also called massive timber] is produced by stacking strips of spruce crosswise and gluing them together under high pressure—essentially creating giant panels of super-plywood. The angled layering of CLT is the key to providing immense structural integrity, allowing the pre-cut panels to bear loads. Customizable in size and thickness, CLT behaves more like concrete slabs than lumber beams—and some of Stadthaus’s panels reach up to a foot thick. Whereas a conventional tall building may rely on a steel skeletal frame with beams and columns, CLT panels distribute the weight of the entire structure evenly, fitting together like a massive piece of Ikea furniture—albeit far sturdier.
The construction of Stadthaus proceeded in an Ikea-like manner as well. Thanks to the modular pre-assembly of the CLT panels, the completion of Stadthaus was remarkably speedy. Four workmen finished the project in just seven weeks, cutting the labor cost by approximately 30% against conventional steel and concrete construction. And so, while CLT is more expensive than traditional materials, its price was largely recouped in saved labor.
Technological advancements have quelled the single largest concern with wood as a primary material: fire. In a blaze, CLT’s outer layers char and seal the interior, keeping the building up longer. In testing, CLT has outperformed steel, which melts at high temperatures.
Perhaps wood’s greatest appeal, however, is its role as a sustainable resource. Wood is, of course, entirely renewable. It’s also nearly unbeatable when it comes to its carbon footprint. While producing steel and concrete requires the production of massive amounts of carbon, trees capture and store it. And so, timber represents locked carbon, or “embodied energy.” With 186 tons of carbon locked in its timber panels, Stadthaus is actually a carbon-negative building, offsetting its cooling and heating costs for the first twenty years of its existence.
While CLT and its ilk are promising advancements in reconsidering wood, we must be careful when we sing wood’s praises. In the United States, we still rely on cheap fast-growth lumber in framing most of our houses and end up paying dearly for it down the line. Wood stud framing is susceptible to rot, termites, and fire—and performs poorly in natural disasters.
Until CLT becomes more commonplace and less expensive, we’re in dire need of residential building code reform. What we may see is a cross-pollination of building materials, with taller buildings using wood and houses incorporating concrete, masonry, steel, and eventually CLT. It may also take a wide, international revision of building codes, as Stadthaus was able to proceed mainly because it wasn’t expressly prohibited in European building codes. To reap the benefits of more environmentally friendly applications, our codes have to keep up.
What is clear is that it’s time for a reassessment of our prejudices and assumptions about materials. Today there are plans for ever-taller wooden buildings around the world. The HoHo project in Vienna, currently underway, will stretch to 24 floors and 276 feet. It will save 2,800 tons of carbon dioxide emission in total and just might usher in the age of the wooden skyscraper—or the “plyscaper,” as some have begun to call it.
Perhaps in the future, we’ll be looking at entire cities of wood, remembering the short and strange age of concrete and steel.
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