Seattle Sets the Trend for Mass Timber Building

As buildings have gotten larger over the years, wood structures have mostly fallen by the wayside. This is especially true in cities which need buildings with a significant maximum occupancy. For years, it was impossible to imagine a wood or timber building in such a city.

But that is slowly changing. The Builtt Center is the first mass timber building in Seattle since the 1920s. It’s 6 stories, made almost entirely out of mass timber, is up to code and conforms to the “Living Building Challenge.”

It is likely that buildings such as this will become the norm. So, let’s take a closer look at what makes the Builtt Center, and similar mass timber projects, worth the investment.

Safety

While the first reaction to a multistory mass timber building may be concern, wood is actually a much safer building material than steel or concrete if used properly. For example, in a fire steel can melt and become unstable in under an hour – the typical test to ensure that people will have time to safely evacuate. Mass timber, however, burns more slowly and can last longer than one hour.

So for the Builtt Center, the designers settled on larger, stronger mass timber beams that would perform better in case of fire, and maintain structural integrity for a longer period of time. Sizes range from 5-1/8” x 15”, up to 12-1/4” x 21 inches. Additionally, the steel connectors used at the joints of the building were installed with fail safes that ensure they would not fail if exposed to intense fire.

Also, to avoid shrinking, a glulam wood columns system with vertical grain orientation was implemented. There are also steel tubes set in each joint.

Environmental Factors

Using mass timber may also seem environmentally dubious. But just like with safety, the opposite is true. If you source wood from a responsibly managed forest, it is actually better environmentally than steel and concrete.

Mass timber leaves less of a carbon footprint, as it will store carbon for the entire 250 year lifespan of the building. In the case of the Builtt Center, the wood was acquired from certified mills within 600 miles of its location. This wood had to be free of over 360 toxic materials – including adhesives and finishes -- in order to be in line with the Living Building Challenge. These standards are even more rigorous than building code.

Architect Brian Court said of these efforts, “A lot of people were surprised to learn that a wood structural system was possible here, but this project helped them learn about wood’s environmental advantages in terms of embodied energy and life cycle assessment. Wood really outperforms steel and concrete in the right applications. With this project, we think perceptions about wood are going to change.”

Additionally, the Builtt Center is run on 100% on-site renewable energy and all the water is harvested rainwater. There is also on-site waste management.

Cost

The Builtt Center cost considerably more than comparable buildings. At $32.5 million and $577 per square foot, it cost 23% more than other buildings of its size.

However, construction costs alone were only $50 more per square foot. And with a life expectancy of 250 years – at least 5x the average of comparable structures – it seems to be worth the cost. The designers also believe many of the costs of such buildings will be mitigated as this becomes more normalized.

Court describes this as an investment, noting that, “This building has essentially prepaid utility bills.”

And Seattle’s Built Center is not the last mass timber building to be designed and built. Across North America, designers are drafting plans for buildings at least twice its size. And so, just like trends in the past, Seattle is ahead of the curve with environmental, safe mass timber.

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