Wooden Skyscrapers: meet the future of cities skyline

written by Noemi Muratore

Photo credit: Sumitomo Forestry

Skyscrapers are often pictured in common imagination as huge buildings standing amidst others with their shiny glass windows and concrete walls. However, this stereotyped New York style vision is slowly but surely changing thanks to the advancement of technology and a renewed sensitivity to environmental issues. A Japanese company, Sumitomo Forestry, inspired by the rich forests that cover the rolling Japanese hills, is currently undergoing an ambitious project that will design the world's tallest wooden building – over 350 meters tall- set in Tokyo. The company  set the goal to make use of wood as their primary construction material: over 9 out of 10 parts will be made of wood, while the remaining will go to steel and other traditional construction materials.

Japan leading the innovation path 

Almost 70 floors full of fashion shops, offices, hotels and 8000 private homes, with trees and foliage on balconies at every level to give a better idea of what green architecture really means. These architects believe that trees and nature are a crucial driver to reach happiness.  That's why they are projecting environmentally-friendly, timber-utilizing cities that could look more like forests rather than like a mass of high-rise buildings.  Due to its critical exposure to earthquakes, Japanese architects and engineers have struggled over the years to find a way to build solid yet flexible constructions. To avoid catastrophes, the new wooden skyscraper will incorporate a structural system composed of braced tubes made of columns, beams and a diagonal steel vibration-control braces at the center of a 350m (1,150ft) wood and steel column, to prevent deformation of the building due to lateral forces such as earthquakes or wind. Although representing an important step towards the diffusion of technologically advanced and ecological buildings, this project is still far from easy to realize and incredibly expensive. With its 185,000 cubic meters of timber, the costs are expected to swell by up to around 600 billion Japanese yen ($ 5.6 billion). Twice the amount of a conventional high-rise building constructed with current technology.

Ambitious projects around the world 

The Japanese wooden skyscraper is just one of a handful of ambitious ideas that have popped up in the past couple of years. Designers have proposed a scheme for an equally tall wooden skyscraper in London called Oakwood Tower. In Stockholm, a company is planning to build a 436-foot to use as a residence, it will be the tallest in the city. And Zaha Hadid's firm recently won the commission to construct an undulating, all-timber soccer stadium in England. At the moment there are few timer towers in the world and the tallest one is an 18 floors dormitory for students at the University of British Colombia.

Reasons for switching to timber

Up until the late 19th century, timber was still the dominant building material. After a series of brutal city fires across major American cities, architects started considering the flammability of wood as an important disadvantaged and therefore began with the exploration of new materials like steel and concrete. The latest innovation is based on a cross-laminated timber, a kind of super-strong plywood, made by gluing together different levels of wood to form a layered composite that is as strong as steel, if not even more. This new material, paired with precision digital manufacturing processes like CNC milling, allows architects to build with timber at unimaginable heights just a century ago. Moreover, timber has nothing to do with polluting materials: it is both light and strong, which means it's well suited for tall towers that must hold their own weight. At the same time, it's not as stiff as steel and concrete, which limits the distance it can span while still retaining its strength. Timber is also very sensitive to moisture so fire is no longer a big.  Wood is one of the most innovative building materials coming straight from mother nature. Its production generates no waste products and it binds CO2, while concrete and steel buildings leave behind a carbon footprint and are thought to be responsible for about 8% and 5% of global emissions respectively. Wood has low weight but is a very strong load-bearing structure compared to its lightness. Wood is also more fire resistant than both steel and concrete. This is due to 15% of wood mass being water, which will evaporate before the wood actually burns. To conclude it makes easier to control the temperature inside a closed space and can be exposed without being covered with plaster or other costly materials.

Research has still a long way to go before the multiple implications and uses of wood can be explored, but of one thing we can be sure: in 20 or less years our cities’ skyline might look much different- and a lot greener!