CLT offers variety of approaches to strucural systems
Two developments are both breaking ground this year and, although they have completely different structural systems, have one key material in common: cross-laminated timber.
The two new projects that are helping move the needle for mass timber design in the U.S., structurally and aesthetically, are the Eastside Office and the First Tech Federal Credit Union headquarters in Hillsboro, which broke ground in August. Eastside Office's groundbreaking is slated for early 2018, and both are designed by Portland-based Hacker Architects.
The Eastside Office is a six-story building with glulam (glue laminated) columns and beams and cross-laminated timber floors, fully visible throughout the interior. It's a nod to the timber-heavy past of the neighborhood, and is planned to be 90,400 square feet.
The half-block site is located at Southeast Stark Street and Martin Luther King Jr. Boulevard, adjacent to the Portland Music Company in the Buckman neighborhood. The development team is a collaboration between Beam Development and Urban Development Partners.
The First Tech headquarters, located in Hillsboro, clocks in at 150,000 square feet — one of the largest CLT buildings in the nation in terms of square footage. The wood structure also uses glulam.
The Business Tribune checked in with two architects from Hacker, a firm with an environmentally progressive focus over the past 30 years, who are working on the projects.
David Keltner is the lead designer for Eastside Office and Corey Martin is the lead designer for First Tech.
"What's interesting about them is that they actually represent two totally different ways you can use that structural system, so the Eastside Office building is pairing that glulam and cross-laminated timber structure with a concrete elevator and stair core, and also concrete poured over the top of the cross-laminated timber floors," Keltner told the Business Tribune. "Whereas the First Tech building doesn't use concrete — instead it uses a steel frame in the center of the building and then uses steel strapping in the floor system."
More specifically, the buildings also represent two different ways to handle shear loads, which are important in case of an earthquake.
"It's a weight versus capacity thing: they're both doing the same thing," Martin said. "The steel one is lighter and can ostensibly go up quicker than the concrete can because you've got to pour more. It's not clearly better, it's just a different approach."
The Eastside Office has exposed concrete, to show off the concrete and the wood. Martin said it was "a bit of a premium."
Hacker has three — and soon four — large office buildings under construction in Portland, each with a different structural system. The Field Office at the top of the Pearl District is all steel, and Station Place Lot 5 in the Pearl District is all concrete.
"Then we started First Tech, which is the first all timber one with the steel frame, and now the East Side office is timber with concrete cores," Keltner said. "There isn't a clear structural system that's the go-to system that solves everything — they're all in play, for all kinds of different systems are getting considered. Typically, there will be one way based on a region or specialty, but because of the advent and advances in wood frame technology, that's gotten pretty competitive with the steel and concrete."
How CLT pencils out
The cost comparison of CLT is difficult because although it can be expensive itself, it can make other pieces of the project cheaper — or unnecessary.
"If you just compare that structural system against another structural system, the wood is more expensive significantly," Keltner said. "You do save some time in the schedule with wood versus steel, so that's a saving. Depending on how you use it, the way that you route all the different systems through the two different systems can be different."
In the end, as a whole building system, it's competitive even though it is a challenge to give-and-take on other parts of the system.
"Most of the projects we're talking about are being built by people who really are about long-term impact and long-term value to them," Martin said. "They're committed to figuring out how to make it work."
CLT is marketed as decreasing a development's construction timeline because it's pre-fabricated off-site.
"The interesting thing we've learned is that while some people might hope that would realize a shorter construction schedule, you do get a little improvement, but the structure goes up so quickly the other systems that follow the structure — like all your windows and walls — can't go that fast, so you can still only build as fast as the next slowest thing," Keltner said. "Until we figure out how to build all the parts off-site and have them all show up, that system isn't going to realize the kind of schedule benefits that people who sell the system might promote."
There has already been movement toward unitizing the systems in Portland, although it hasn't been completely solved yet.
"While there is some, no one has really realized that kind of schedule advantage of the CLT because of not having modularized components — although there are some projects that are starting to," Keltner said.
CLT for Oregon's economy
"This kind of tech is really important to the state and to our economic future as a state because our timber lands are more and more challenging and expensive to harvest, and you have to be more careful about harvesting and more thoughtful," Keltner said. "That means all the trees that do come out, you want to add value to those. We, as a state, are moving from an extraction economy — cutting a tree down and shipping it out — more to what is the value you add to that tree after you take it out of the forest."
Keltner serves on the board of Oregon State University's research on forest lands and timber tech, with the goal of making sure Oregon has a strong, sustainable economy.
"We've been known over the years for being really innovative in the use of wood in the region and finding ways of using it more and more, not only as a finish or cladding, but making the structure of buildings out of it," Martin said. "The result is beautiful, the kind of space you'd want to be in, and extremely humane."
Another big reason to use it is the pure beauty of the system.
"It also has incredible benefits in terms of sustainability — that was hugely important for the developers of the product in the beginning, that it's obvious a renewable resource, it's a carbon sink," Keltner said. "And in particular for us in the Northwest, I've always felt the Northwest is the place for this kind of tech to get developed because — especially in Portland where we have the urban growth boundary — we need to get, in terms of development, a way of applying a rapidly renewable, local resource that is also a carbon sink to improve our city's ability to live more densely by building higher buildings out of it."
The future of CLT
"The U.S. in terms of building tech always seems to be late adopters — we're really late to the game," Martin said. "An architect in our office, Alex Zelaya, took two months and basically did a trip around the world looking at how high-tech wood is being implemented around the world."
Keltner himself saw all-wood buildings going up in Germany, Austria and New Zealand upwards of 10 years ago, and was inspired to figure out how to do it here — over the past five years, he's been gaining knowledge on it as it became a possibility.
"It's instrumental in these projects in helping us understand what the possibilities are, and helping us understand how to push our suppliers to think about what's possible," Martin said. "When (Zelaya) got back from that trip it was abundantly clear we are way behind what's happening in the rest of the world around this tech: it's already done."
Part of the lag is due to policy and stringent building codes — in particular in the Northwest, seismic requirements.
"It hasn't been for lack of the system being around — it's been in the world a long time — it's what our legal code review and requirements are that are needing to change in order to get up to speed with tech that's been around awhile," Keltner said.
Hacker wants to do more CLT buildings, and has two other projects in the office with CLT that are still under wraps.
"There are buildings back a long time ago in other places where they built purely wood buildings, didn't even add extra insulation, making them more passive and using wood as thermal mass," Martin said. "As sustainability becomes a more and more highly adopted as a rule everywhere, this system will become more and more valued."
The Eastside Office is slated for completion June 2019, and the First Tech building is slated for spring 2018.
By Jules Rogers
Reporter, The Business Tribune
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