Sidewalk Labs is building a smart city entirely of mass timber. What could go wrong?

North America is on the cusp of a mass timber revolution, and Sidewalk Labs’ Waterfront Toronto project is leading the way. But the smart material faces major obstacles.

A building made primarily of wood conjures public fear of fire, but for a growing number of developers, it evokes opportunity. From constructing towering wooden condominiums, to timber college dormitories, to an entire neighborhood built from trees, experts in “mass timber” are creating buildings of the future. 

Sidewalk Labs’ master plan for a futuristic smart city on the waterfront in Toronto includes an entire neighborhood made of wood, called Quayside, with 10 mixed-use building up to 35 stories. 

The plan is audacious, considering that in the U.S., there are only 221 mass timber buildings in the works or fully built, according to the American Wood Council​’s Kenneth Bland. 

In most U.S. cities, mass timber buildings, and specifically tall mass timber buildings, are a rarity, if they exist at all. 


But architects, city officials and timber advocates across North America are pushing conventional building codes and public perception because of the drastic impact these structures can have on reducing CO2 through carbon sequestration, compared to traditional concrete and steel.

“I think it’s a big opportunity for a lot of cities out there … The impact on reducing carbon emissions on earth could be dramatic,” Karim Khalifa, director of buildings innovation at Sidewalk Labs, told Smart Cities Dive. “And that gets me excited.”

What is mass timber?

One of the biggest obstacles for city officials is understanding the material. They are more than buildings made of wood — they’re defined by their structure. Steel or concrete buildings with wood accents don’t count, according to Andrew Tsay Jacobs from architecture firm Perkins and Will.

Mass timber buildings use solid wood panels to frame a building’s walls, floors and roofs, creating structures that can reach at least 18 stories, as is the case with the tallest mass timber building in the world in Norway. But these buildings aren’t just pure wood. Mass timber construction utilizes engineered wood, or panels glued together, and there are several types: cross-laminated (CLT), glue-laminated and dowel-laminated timber, with CLT being the most common. 

While shorter wood buildings have existed for centuries, CLT panel technology is relatively new. It was developed in Europe in the 1990s, the material was only added to the international building code in 2015. Even then, all-wood buildings were capped at six stories, though that will change to allow taller structures in 2021.

Why use mass timber?

A main argument for the use of mass timber is its power to mitigate climate change. The structures can have a lifespan of hundreds of years, and contain the unique ability of effectively sequestering or removing carbon from the atmosphere, which can reverse climate change effects at a large scale. 

“Now more than ever, the lens through which we view and imagine ways to redesign and build physical infrastructure, has to be based around sustainability,” said Portland, OR Mayor Ted Wheeler during a speech at the International Mass Timber Conference in March. 

According to The Climate Trust, a piece of land with no building on it has a higher carbon footprint than a piece of land with a CLT building. Karim Khalifa says he likes to think of his Quayside designs not as buildings, but as big timber [CO2] vaults.

The material is also renewable, says Ben Kaiser, owner and principle at Kaiser Group and Path Architecture, a design and development firm. “We grow our structural core in our forests. We don’t grow concrete and steel in our forests,” Kaiser told Smart Cities Dive.

Wooden buildings also weigh significantly less, and for buildings constructed on seismic plates, the lighter load performs better during an earthquake. The Carbon12 building in Portland weighs 75% less than it would if built with steel and concrete. “That is just a mindblowing statistic,” said Kaiser.

Wheeler echoed these benefits in his remarks at the timber conference. “[CLT is] also noted to be strong enough to withstand wind impacts during hurricanes and earthquakes,” he said. “When we think about preparing for our changing climate and the uptick in these types of natural disasters, a product like CLT becomes that much more appealing.”

How is the mass timber trend growing?

Design competitions are fueling growth in Oregon and California by financially incentivizing architects and developers to use the material. California is holding its first-ever “mass timber building competition” in 2019, administered by the nonprofit WoodWorks, to award one or several developers $500,000 in grants for their designs. 

“Demonstration projects are needed in California in order to promote mass timber usage and to increase familiarity at the local permitting and approval agencies,” said California’s GovOps’ website.

Sidewalk Labs held multiple public forums on Quayside for mass timber experts to offer feedback, encourage debate and learn about the material, as well as quell potential backlash.

We conducted, so far, two industrial forums with all the timber-interested parties in Canada,” said Khalifa. Concerns like fire safety, supply chain and the factory were brought up, and Khalifa cites the opportunity for feedback as extremely important and ongoing.

Right now, experts say the most growth in the industry will come in the form of shorter tall mass timber buildings, as Oregon and Washington are the only states to permit mass timber buildings in this height range. Building in the 7-12 story range, as opposed to 12-18, is more realistic for now, experts say.

“There’s going to be certain heights of buildings that are the sweet spot, if you will, for mass timber … That sweet spot is going to vary from state to state,” said Bland. 

Atlanta’s new T3 (tall, timber, technology) building made of heavy timber fits into this range, and it required “lots of coordination with city planners,” according to the Atlanta Journal Constitution (AJC).

“Before the city signed off on T3, inspectors and the building’s architecture and construction teams held numerous meetings on structural integrity and reviewed load calculations, floor systems and fire resistance,” said Gregory Pace, interim director of the office buildings within the city of Atlanta’s planning department, to AJC.

What’s stopping mass timber?

Even vocal mass timber advocates admit that every step toward constructing CLT buildings of the future poses a different demand, proving to be much more time intensive than constructing a steel or concrete building. Timber supply, building codes and investments have been obstacles to the growth of mass timber.

Supply and demand

The Architect’s Newspaper explores the state of mass timber — the schools, organizations and production facilities across the U.S. — through a series of interactive maps. As compared to steel and concrete sources, of which there are thousands throughout the country, the sources are limited.

Quayside’s proposal specifically necessitates the construction of an $80 million CLT production facility in Ontario, to supply the material, which could also ease the process of future CLT buildings in that area.

Building codes

Tall mass timber’s absence from the International Building Code means construction with this material currently involves years of research, development and testing to make special state and city exceptions, on top of the already intensive construction process. In 2021, it will still be up to individual jurisdictions to adopt the mass timber code. Washington and Oregon have been proactive in adopting the code through a state amendment and California is in the process of doing so. 

“For four decades, [building code] has been a pretty hard barrier to get through,” David Weihing, principal at engineering consulting firm Thornton Tomasetti, told Smart Cities Dive.

Investments and backlash

The research, testing and development needed to construct with mass timber requires more time and money than traditional building structures.

“There needs to be more research,” Mark Rudnicki, professor at Michigan Tech University’s School of Forest Resources and Environmental Science, told Smart Cities Dive. “We’re moving forward with that, but there needs to be more resources in here.”

Even if private developers can secure the funding and change the code, public projects like Quayside are getting backlash from citizens who are afraid the material is more susceptible to fire. While mass timber buildings’ columns and beams chars from the outside-in, in a way that slows combustion, public opinion and fear is hard to sway — and rightfully so, said Khalifa. 

“In San Francisco and Chicago where timber wood buildings burned, it put a real scar in our psyche about how timber wood buildings will perform in the future,” said Khalifa.

City officials also have to consider backlash from the concrete and steel industry when changing building codes. As the market for CLT is expected a CAGR of 9.1% over the next five years, according to MarketWatch, “there are sectors that don’t want wood to succeed, because it would take a bite out of their market,” said Rudnicki.

What does the future look like for tall mass timber?

Cities and states across the U.S. are adapting building codes to permit tall mass timber buildings. Weihing points out that Chicago recently updated a building code that hasn’t changed for 70 years, and allowed their first CLT building in 2018: a flagship McDonald’s restaurant. 

Minneapolis and Milwaukee have also taken the lead in granting building code exceptions or changing regulations to allow tall mass timber buildings, and large cities like New York City have made moves toward allowing tall wood construction, according to Construction Dive.

WoodWorks tracks CLT projects in design, construction and fully built. While not every building in design reaches completion, the numbers at every phase are growing.

Kaiser’s original appeal for his Carbon12 CLT building in Portland received doubt at every turn, he said, but now, two-and-a-half years later, “the whole tenor has changed.”

“The question now, from the city’s perspective, is not whether these tall wood buildings are possible, but rather, how can we assist you in getting this done as quickly as possible,” said Kaiser.

Whether Quayside comes to fruition depends on: budget, the creation of entire CLT production facility in Ontario, public backlash over data governance and local city government.

“It’s almost like rewriting the codes to be specific to a development of this scale and the material that people are not accustomed to,” said Weihing. “So it will take a buy-in.”

However, Khalifa says that the project is already paving the way for something similar in the U.S. City governments just need more experience and training with the material for it to take off.

“I think we could see cities could empower people to try and do pilots and study them carefully and safely. [But] they need also to help their city officials be able to review those projects,” said Khalifa. “They need training and education.

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