Building skyscrapers with wood

Building skyscrapers with wood: it sounds bizarre, unsafe, and perhaps even a bit far-fetched. But it may actually be the future of the construction industry.

“Every building material has its own advantages and disadvantages, and there is no reason to exclude wood from mainstream building materials. While we cannot definitively say that wood is better than steel or concrete, we should give wood its rightful place,” said Todd Snapp, an architect at the architecture firm Perkins + Will.

Todd Snapp is the design lead for the company's River Beech Tower project, an 800-foot residential skyscraper constructed almost entirely of engineered timber. The company is responsible for the planning and design of an area in downtown Chicago, and the building is part of that plan. A project at Cambridge University called the Natural Material Innovation Project contacted Perkin Wills and recommended the concept of a wooden skyscraper. They hoped to realize a real-world architectural project with a wooden skyscraper. This project would help the Cambridge University project team further refine the project's structural form, construction methods, and other relevant information.

River Beech Tower architectural rendering

Of course, the River Beech Tower is currently still a purely conceptual project, with no actual construction or development plans yet. However, the project aims to prove that the idea of ​​a wooden skyscraper is feasible.

Perkin Wills isn't the only firm experimenting in this area. Many cities, like London and Stockholm, are undertaking similar projects. UBC in Vancouver, Canada, and Minneapolis, USA, have already built 18-story timber-framed buildings, while timber-framed buildings exceeding 10 stories have sprung up in Norway and New Zealand.

Perkins + Will was founded in Chicago in 1935. The city survived the devastating Great Chicago Fire of 1871, which led to steel and concrete replacing wood as the primary building materials. The most iconic example is Chicago's iconic Wrigley Building. A concrete building was just a stone's throw from the River Beech Tower project. Therefore, restoring wood to its former status in the construction industry remains a long and arduous task.

What are the advantages of using wood to build structures?

Okay, there are a few reasons.

On the one hand, wood is lighter and more flexible than steel or concrete. For example, a wooden skyscraper will experience less seismic force during an earthquake. The lighter weight also saves on transportation and installation costs throughout the construction process. Wood itself is an excellent poor conductor of heat, which can save heating and cooling costs for building owners and residents.

On the other hand, because wood is so light, it poses a swaying problem in windy areas – especially for high-rise buildings. For the River Beech Tower project, Snapp and his colleagues actually addressed this issue by using triangular and diamond shapes to construct the entire building. Triangles are a more stable structure than rectangles, so this triangular wooden structure can withstand stresses from all directions. This interesting shape also presents a "honeycomb" architectural aesthetic. Key load-bearing connections within the building will be reinforced with reinforced concrete. Furthermore, the entire skyscraper is primarily constructed using 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 using large-scale glued laminated timber (GLLT) members for the entire bottom third of a building could provide sufficient structural stability. To achieve this, they designed the building as two skyscrapers connected by an atrium. This allowed them to extend the building's base and achieve the necessary substructure stability. It also provided a large open space for the building's core, opening up more possibilities for the structural and interior design of the superstructure.

Artist's rendering of the River Beech Tower project

Another interesting aspect of wood is its ease of use compared to steel or concrete. The problem with concrete is that you have to pour it, and it requires a curing time, often several days or even weeks. Steel components, on the other hand, are very complex and expensive if you want to create intricate shapes. Wood, however, can simply be cut. Now, computers and modern technology allow wooden components to be precisely and easily processed in factories.

The highly prefabricated and workable nature of wood allowed the River Beech Tower team to be creative in both the construction process and design. They devised a plan for the building to be constructed from standardized timber modules, all prefabricated in a nearby factory and then transported to the construction site. This modular approach is not unheard of in standard structures. Prefabrication saves significant time while allowing for better quality control.

Of course, any conversation about building skyscrapers with wood raises fire concerns. In fact, engineered wood materials manufactured using modern techniques are extremely fire-resistant; they actually require extremely high temperatures to ignite – even under intense heat, glued laminated beams maintain their structural integrity for a certain period (the fire resistance time required by fire codes) due to their surface carbonization. Steel structures, on the other hand, are not actually fire-resistant because when steel reaches a certain temperature, it begins to melt and even crack. (Think of the Twin Towers in the 9/11 attacks.)

Finally, it's worth mentioning that building more skyscrapers with wood will make the world a lower-carbon and cleaner place. Of course, regardless of the materials used, carbon dioxide emissions will occur. Steel and concrete are recognized as carbon-intensive materials: for example, 60% of concrete emissions come from the chemical reactions involved in its manufacture. Replacing large amounts of steel and concrete structures with wood could save us a significant amount of carbon dioxide emissions.

Most importantly, wood is a natural material, like corn or potatoes; it is renewable. Increased demand for it will increase the economic incentive to plant more trees. What we need to do is ensure that the timber used to build wooden structures comes from legally managed, sustainably managed forests. Planting more trees and using wood is an excellent option for addressing climate change.

Advances in engineering technology have led more and more architects and engineers to realize the possibility of bringing timber back into the mainstream construction market. There is a long way to go, including changes in building codes. While wooden skyscrapers are still an emerging field, like the trees they depend on, they may grow into a mainstream form of construction in the future.