The Rise And Rise Of Wooden Skyscrapers
W350 Project, Sumitomo Forestry, Tokyo. Photograph courtesy of Sumitomo Forestry & Nikken Sekki
Natural materials are making the concrete jungle more sustainable.
A new skyscraper is taking shape on the outskirts of Vienna. Nothing unusual about that, of course. But this building is unlike its neighbours. Instead of bricks and mortar, it is to being constructed from wood. The Holz Hochhaus (“wood skyscraper” in German), or HoHo, is, appropriately enough, surrounded by forest. When completed next year, its 24 storeys will house apartments, offices and a luxury hotel. The HoHo is a taste of the future, and may just revolutionise our cities’ skylines. With architects constructing wooden towers everywhere from Canada to Norway, you may not be able to see the trees for the wood.
There’s the 11-storey Framework apartment building going up in Portland, Oregon, and Forte, a 10-storey block of flats in Melbourne. Both have pushed the boundaries of current technology in terms of size. Just outside Oslo in the small town of Brumunddal, the Mjøstårnet, an 18-storey wooden skyscraper, is rising above the crystal-clear waters of Lake Mjøsa. An 80-storey skyscraper, the River Beech Tower, has been proposed for Chicago’s waterside, and in Tokyo, the Sumitomo Forestry Co has published detailed plans for a vast, 70-storey tower made of wood, with only the stairs and lift shafts being constructed out of concrete and steel. The W350 tower, as it is known, is due to open in 2041 to coincide with the company’s 350th anniversary.
Wood is one of the most ancient building materials. Temples in Japan, including Honju-ji from the late 1500s, and 12th-century churches in Scandinavia made from trees have stood for centuries. Wood was the go-to, but over the past 200 years, it has been superseded by iron, steel and concrete. However, these new towers are disrupting that. Wooden skyscrapers are not just changing cityscapes; they are also turning conventional architectural thinking on its head. Wood has not been used to its full capacity until now, according to Mjøstårnet architect Mr Øystein Elgsaas. “Mjøstårnet is our first building where we really exploit the tree’s properties to the fullest as a construction material,” he says.
Framework, Portland. Photograph courtesy of LEVER Architecture
“Wood has an enormous load-bearing capacity at low dead weight,” says Ms Caroline Palfy, who is in charge of building the HoHo. In other words, it is great at doing the very basic and important job of making a building stand up. In fact, wood’s strength-to-weight ratio is 20 per cent higher than that of steel and often better even than concrete. “Wood is stable and elastic at the same time,” says Ms Palfy. “It is also versatile and has a positive influence on the indoor climate as it absorbs and releases a lot of moisture. In Austria, we are surrounded by forests.” Wood is also better at insulating, and therefore keeping heat in – 15 times better than concrete, 400 times better than steel and 1,770 times better than aluminium.
It makes you wonder why we left wood by the roadside in the 19th and 20th centuries. This was, in no small part, because inexpensive energy made concrete and steel cheap to produce. Architects chose those materials because they allowed for enormous stylistic creativity. You couldn’t make a breathlessly bonkers Ms Zaha Hadid masterpiece out of wood and you probably never will be able to. You’ll always need concrete and steel for curves and crazy shapes. But curves and crazy shapes are not everything.
When it comes to timber buildings, architects and engineers are learning from each other, just as they did during the first skyscraper boom at the start of the 20th century. And where architects are pushing for bigger, more elaborate designs, the engineers are rising to the task.
Mjøstårnet, Norway. Photograph courtesy of Voll Arkitekter AS
The world’s current tallest wooden building is Brock Commons Tallwood House, an 18-storey hybrid mass-timber student halls at the University of British Columbia in Canada. It uses cross laminated timber (CLT) beams. CLT is the part of the puzzle that has allowed wooden buildings to go from two storeys to 20. CLT involves sandwiching wood together to make it thicker and stronger. It also makes it less tasty to termites and even more resistant to fire, therefore perfect for building upwards.
Wooden buildings actually perform well in fires, contrary to popular belief. Wood burns in a very specific way. It’s subject to pyrolysis. Gasses in the wood burst into flames, but the outer part of the burnt wood becomes charred and this in turn protects the inner layers. Flame-retardant paint can also be used to further mitigate fires spreading.
Brock Commons is in Vancouver, which is also home to Mr Michael Green, the architect who has done perhaps the most to promote wooden buildings. He’s had a busy year. Mr Green has just sold his eponymous architecture firm to Katerra, the tech company founded by former Tesla CEO Mr Michael Marks. Katerra has made waves with its plans to disrupt the construction industry – wooden buildings are a key part of that. It has raised staggering amounts of capital, and aims to be one of the dominant construction firms of the future by bringing Silicon Valley thinking to construction.
Stockholm HSB plyscraper. Photograph courtesy of C.F. Møller Architects and Dinellohansson
Central to this is Katerra taking a punt on wood being the natural future of architecture. In 100 years’ time, wooden skyscrapers may well become the norm, maybe even the only way of building up. There’s one huge reason for this: energy. The enormous amounts of energy (and, by association, cash) needed to make concrete and steel are mind-blowing. Both need heat, water and raw materials. Everything has to be mixed and manufactured, then delivered. You need to burn a lot of fuel to create a finished skyscraper. Wood uses far less energy and is a natural material. It even absorbs carbon rather than creating it. Coniferous trees can be grown quickly, some of them in just a couple of years. Once you’ve harvested one batch, you simply replant. Another advantage with wooden buildings is that they’re quick to put up. Some can be constructed in weeks rather than the years that regular skyscrapers require.
Visualisations for plyscrapers with cladding look like Billy bookcases on steroids. So these majestic timber buildings are often covered in all kinds of strange coatings. Waugh Thistleton has been creating magnificent and innovative all-wood towers in east London. Its nine-storey block at Murray Grove in Hackney was the world’s tallest completely wooden building for a time, and its new housing development in Dalston is the world’s biggest (by area) CLT building. Yet the Murray Grove block is covered in panels and the Dalston flats are coated in bricks to fit in with a conservation area. Wouldn’t it be great to see the wood in all its glory?
Not necessarily, says Mr Lloyd Alter, an architect and design editor of treehugger.com. “These tall timber towers can be too much of a wood thing,” he says. “Architects who really understand the material are designing buildings that take advantage of the true attributes of the material. So, for example, Waugh Thistleton’s Dalston housing is almost Victorian in its design – relatively low and broad and built around courtyards. It is relatively simple to engineer and construct. In successful cities around the world, the great need is housing, not fancy towers. Wood construction, either in cross-laminated timber like Dalston or in panellised construction like they do in Scandinavia, can deliver it in wood quickly and affordably.”
Brock Commons Tallwood House, Vancouver. Photograph by Michael Elkan, courtesy of Acton Ostry Architects & University of British Columbia
A building is characteristically a boast; a tall one, especially so. But a building made of wood possesses better manners and better morals. By going back to nature we’re atoning for our past building sins, for the eco-unfriendly swagger of concrete and the American Psycho bolshiness of glass and steel. “These plyscrapers will be the most beautiful buildings we’ll have,” says Mr Green. “I love to say that Mother Nature holds the greatest patents.”