Swinerton Builders self-install CLT
The five-story First Tech Federal Credit Union office currently under construction in Hillsboro will be the largest cross-laminated timber (CLT) structure in the U.S. by square footage.
"We think the record will stand for at least another six months," said William Silva. "I'd say the CLT mass timber industry is more mature in Europe since the late '90s, and in Canada for the last 10 years, and so in those markets contracting is different. In the U.S., we're one of the few (general contractors) that has done self-installation."
Silva is a preconstruction manager at Swinerton Builders, the general contractor on the First Tech project.
Because wood buildings are back in style now that technology has facilitated its efficiency, it's common for a subcontrator to install the new material — but Swinerton is one of the few GCs currently self-installing CLT in Oregon.
"One of the keys we found is that everybody, when it comes to mass timber and CLT, is enamored both with the aesthetic and potential of speed of erection, but really what we found is it's 90 percent pre-planning and prefab, and 10 percent about execution," Silva said. "If you take the right steps, you can employ lean construction principles and really be a lot smarter, so you can install it quicker in the field."
Pre-fabbing shorter construction times
At the First Tech site, CLT is an element of the mass timber frame used for the decking construction. Glulam columns and beams form the supporting structure.
"Almost like industrial furniture, (timber) has an aesthetic, but one of the things helping it be more cost-effective is the evolution of the connections," Silva said. "If you go around the half-dozen (mass timber) projects complete here in the Portland metro area, you see an evolution of the connection details and a better understanding of how the prefabrication takes advantage of the tolerance: there's a 1/16th of an inch tolerance in the material — that's unheard of in construction."
Steel and concrete are able to be measured to 3/4 of an inch, and Silva said it's like a different level of resolution in the finish.
"Our goal was to focus on the whole building as a prefab, so not just the structural steel and timber packages being prefabricated off site and just assembled on-site, also the MEP (mechanical-electrical-plumbing trades) in prior sprinkler systems," said Chris Evans, Swinerton operations manager. "We wanted to have our MEP train design those so all the pieces could be pre-fabbed off-site, and on-site be just about assembly."
Evans said the industry is already moving toward offsite
prefab in general with other types of building materials, but mass timber lends itself to the movement of prefab construction because of the way it's manufactured in a plant.
"We do a high level of coordinating with the BIM model, which is typically done so people know where they can (run wires or pipes) in the building and have routes," Evans said. "We took it one step further: we do BIM for fabrication, for all our structural trades in the MEP trades, all designing virtually so they could pre-fab off-site and install on-site. That saves a lot of time."
Silva estimated CLT efficiencies achieved a 20 percent faster project schedule, which is especially important during a time of taxed labor supply.
As for the number of workers, CLT can also cut costs there: Swinerton's team to install a mass timber CLT structure is between eight to 10 people; installing steel metal backing construction common for this type of office building takes them 20 workers; and concrete work reinforcement could be 30.
Installation as assembly
It is based in Penticton, British Columbia, Canada. Structurlam Products supplied the whole mass timber system, including CLT for the diaphragms and floor deck and glulam components.
"CLT is a material that works in the Pacific Northwest because we're comfortable building with wood here, but it also opens up a whole new type of construction around prefabrication," said Erica Spiritos, mass timber specialist at Structurlam. "We're not delivering to the site commodity products that get cut to size in the field; we're delivering building components that are already customized for the building, every piece is manufactured to a really tight tolerance, and installation is more an assembly."
Previously, the light conventionally-framed wood could only be built up to five or six stories.
"CLT really shines as an alternative to concrete and steel," Spiritos said. "I would say the primary product type we're noticing in the Pacific Northwest are office buildings, other types of commercial owners, institutional buildings, some academic building. Increasingly, there's an opportunity to build mid-rise multi-family construction with mass timber."
Tech allows CLT to be competitive today.
"CLT has inherent structural benefits: it's strong in two directions, it has a very high strength-to-weight ratio, it's dimensionally stable — those are the properties independent to the level of prefab," Spiritos said. "Tech takes CLT to a whole other level. That's what gives you schedule savings and a safer, cleaner, quicker build site."
Swinerton is also putting up a mass timber building in Colorado and has four other projects in pre-construction phases. The upcoming projects go beyond office use.
Zach Brehm, Swinerton project manager, was involved at First Tech months ahead of time coordinating different trade disciplines including electrical, mechanical, plumbing, structural steel and structural concrete.
"We still have steel and concrete as elements of the structure that are different trades, so coordinating all those different trades and virtual reality ahead of time allows it to be more successful once the materials and boots hit the ground," Brehm said. "That's really the biggest takeaway for us: perfecting pre-planning and coordination upfront so that when we manufacture these components everything fits together and we're able to put it together quickly once it arrives."
More than 1,600 prefabbed pieces of CLT were unloaded at the First Tech site.
"That's many, many truckloads that have to come...once you really hit the Go button and start the procurement chain, some of the wood is probably manufactured only a week ahead of the time it's actually on site," Evans said. "It's a very coordinated effort between the supplier and the contractor to ensure that the timing of delivery meets the speed of construction, and you have to have a very good first guess of what that's going to be."
That's most of Brehm's job, and he uses Primavera project management software to help keep different fabricators' schedules organized.
"Each piece of the building is unique to its location," Brehm said. "All those pieces, each one has a tag on it and is tracked from the whole process of running through the factory, putting it on a truck, where it is on a truck, where it gets to the site, which face goes up, which face goes down, to the point it gets installed."
Evans said his team detailed that they wanted 4,500 holes pre-drilled in all the glulam and CLT for the mechanical and electrical fittings, matched with the concrete.
"That's only really possible if you have a vertically integrated team and delivery method that allows the contractor to be involved early in the design process to make key decisions, so that you can fully take advantage of the possibilities," Evans said.
By Jules Rogers
Reporter, The Business Tribune
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First Tech Federal Credit Union
Contractor: Swinerton Builders
Designer: Hacker Architects
Mass timber manufacturing: Structurlam