Building skyscrapers out of wood

Building skyscrapers out of wood: It sounds weird, unsafe, and maybe even a bit far-fetched. But it might actually be the future of construction.

“Every building material has its own strengths and weaknesses, and there’s no reason to exclude wood from mainstream building materials. While we can’t definitively say wood is better than steel or concrete, we should give it the space it deserves,” said Todd Snapp, an architect at Perkins + Will.

Todd Snapp is the design lead for the firm's River Beech Tower project, an 800-foot residential skyscraper constructed almost entirely of engineered wood. The tower is part of the firm's master plan for a downtown Chicago district. The Natural Material Innovation Project at the University of Cambridge approached Perkin Wills with the wooden skyscraper concept. They sought to demonstrate the wooden skyscraper's potential in a real-world building. This project helped the Cambridge team further refine the project's structural form, construction methods, and other aspects.

River Beech Tower architectural rendering

Of course, the River Beech Tower is still purely conceptual, with no plans for it to be built, but the project aims to prove that the idea of ​​a wooden skyscraper is feasible.

Perkin Wills isn't the only firm experimenting with this approach. Cities like London and Stockholm are also pursuing similar projects. UBC in Vancouver, Canada, and Minneapolis in the United States have already built 18-story timber structures, while buildings over 10 stories tall have already been erected in Norway and New Zealand.

Perkins + Will was founded in Chicago in 1935. The city survived the Great Fire of 1871, but this fire also led to the replacement of wood with steel and concrete as the primary building materials. A prime example is the iconic Wrigley Building. A concrete building was only a stone's throw away from the River Beech Tower project. Therefore, there is a long way to go to restore wood's importance in the construction industry.

So what are the advantages of using wood to build buildings?

Well, there are several reasons.

For one thing, wood is lighter and more flexible than steel or concrete. For example, a wooden skyscraper would be subject to less seismic forces during an earthquake. The lower weight also saves on transportation and installation costs throughout the construction process. Wood itself is an excellent conductor of heat, saving building owners and residents on heating and cooling costs.

On the other hand, wood's lightness can lead to building sway in high-wind areas-particularly for tall buildings. For the River Beech Tower project, Snapp and his colleagues addressed this issue by utilizing triangles and diamonds throughout the building. Triangles are more stable than rectangles, so the wooden triangular structure can withstand stress from all directions. This intriguing shape also creates a "honeycomb" architectural aesthetic. Key load-bearing joints in the building will be reinforced with reinforced concrete. Beyond this, the entire skyscraper is constructed entirely of engineered wood.

Artist's rendering of the River Beech Tower project

Resolving the trade-off between architectural flexibility and rigidity led to an interesting breakthrough. Perkins + Will's computer models showed that if the entire bottom third of the building were constructed from large-scale glulam members, the structure would be sufficiently stable. To achieve this, they designed the building as two skyscrapers connected by an atrium. This allowed them to expand the building's base and achieve the necessary substructure stability. It also provided a large open space in the building's core, offering greater possibilities for the structural and interior design of the upper structure.

Artist's rendering of the River Beech Tower project

Another interesting aspect of wood is that it's much easier to work with than steel or concrete. The problem with concrete is that it has to be poured, and curing takes time, often days or even weeks. Steel structures are very complex and expensive to create intricate shapes. Wood, however, can be simply cut. Computers and modern technology now allow wooden structures to be fabricated with great precision and ease in factories.

Wood's highly prefabricated and workable nature allowed the River Beech Tower team to be creative with the construction process and design. They proposed a plan where the building would be constructed from standardized wooden modules, all prefabricated in a nearby factory and then transported to the construction site. This modular approach is not unheard of in standard construction. Prefabrication saves significant time while providing greater control over quality.

Of course, any talk of building skyscrapers out of wood raises concerns about fire. In reality, engineered wood materials manufactured using modern processes are so fire-resistant that it actually takes extremely high temperatures to catch fire. Even in these intense heats, glulam beams maintain their structural integrity for the time required by fire codes due to their surface carbonization. Steel structures, on the other hand, are not fire-resistant because, when they reach a certain temperature, they begin to melt and even fracture. (Think of the Twin Towers during 9/11.)

Finally, it's worth mentioning that building more skyscrapers out of wood would make the world a cleaner place. Of course, no matter what material you use, it generates CO2 emissions. Steel and concrete are well-known carbon-intensive materials: for example, 60% of concrete emissions come from the chemical reactions involved in making it. Replacing large amounts of steel and concrete structures with wood could save us a significant amount of CO2 emissions.

Most importantly, wood is a natural material, just like corn or potatoes, it's renewable. If demand for it increases, so too will the economic incentive to plant more trees. The key is to ensure that wood used in wooden buildings comes from legal, sustainably managed forests. Planting more trees and using wood is an excellent option for combating climate change.

Advances in engineering technology are now making more and more architects and engineers aware of the potential for bringing wood back into the mainstream construction market. There's still a long way to go, including changes to building codes. While wooden skyscrapers are still a nascent field, like the trees they rely on, they could become a mainstream form of construction in the future.