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The city of Springfield is proceeding with a project likely to produce the country’s first multistory parking structure made of cross-laminated timber (CLT).

鈥淭his is pretty unusual,鈥� said Kent Duffy, SRG Partnership principal in charge of the project. 鈥淲e are aware of one that is being designed in Switzerland, and others are being talked about.鈥�

Plans call for the structure, dubbed the Glenwood Garage, to stand four stories and hold as many as 360 motor vehicles. City officials hope that the high-profile structure will boost the image of CLT as a viable alternative to traditional building materials. That could boost the economies of Oregon communities where substantial timber is grown and harvested.

鈥淪pringfield is fundamentally a timber town,鈥� said Courtney Griesel, economic development manager for the city. 鈥淔or us, speaking about what timber can do on a large scale made a lot of sense.鈥�

The project is expected to complement 50 acres of planned development, including a hotel, retail space and a mix of affordable and market-rate housing. The garage would serve as an example of CLT’s potential, Griesel said.

鈥淲hat better way to show what timber can do than in a garage?鈥� she said. 鈥淭he other piece is we could see how timber reacted in an exposed structure. We may start to open up a broader market for CLT. That seemed like an opportunity worth exploring.鈥�

Use of CLT for the Glenwood Garage presented some challenges, primarily those tied to the elements. Wind and rain are two of the biggest foes of wooden structures. Cars traveling inside can track water, which can then soak into wood. Also, strong winds combined with rain can pummel structural columns.

To combat those effects, designers plan to put a concrete slab over the driving surface. Research is in the works to determine which kind of breathable membrane or coating material should be used to make sure water doesn’t seep through future cracks in the concrete.

Walkways are planned to both help pedestrians navigate the garage and protect the columns from rain.

鈥淭he biggest challenge is making sure the wood doesn’t get damaged by water,鈥� Duffy said. 鈥淲e went through research at the University of Oregon and college of Forestry at Oregon State (University) to deal with those issues.鈥�

Supporting the weight of 360 motor vehicles in a wooden structure is relatively easy. Building codes that govern parking structures require only that they be able to support 40 pounds per square foot of load. Office buildings, by contrast must be able to support 100 pounds per square foot of load. Though vehicles are heavier than people or office furniture, the load is dispersed over a larger area, putting less pressure on any one spot.

鈥淕enerally speaking, cars are not as heavy as some might think when we are talking about building codes,鈥� said Aaron Burkhardt, an associate engineer at KPFF, which is helping engineer the structure. 鈥淧rotecting the material and durability are the two biggest issues.鈥�

Designers are also looking at the possibility of using rocking shear walls in the structure. Such walls rely on a variety of methods to dissipate energy from an earthquake by moving with it instead of trying to resist it. The walls then spring back into place, minimizing damage and preserving use of the structure shortly after a quake.

Rocking shear walls are relatively new and not covered by current building codes. That means additional testing must be conducted to prove they are safe for use.

鈥淲e expect to use it,鈥� Duffy said. 鈥淚t is not a system that is anticipated by the building code. It will be on a shake table probably in July.鈥�

Currently, the Glenwood Garage project is in the design phase. Planners hope to break ground in 2018 or 2019. Officials hope that CLT will be used elsewhere in the 50 acres of development, Griesel said.

鈥淲e absolutely want other parts to be CLT, but we’re not in a position to demand it,鈥� she said. 鈥淚 don’t imagine it will just be the garage that uses CLT, but it still has to pencil out.鈥�