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Portland developer Kevin Cavenaugh has a knack for capturing attention with eye-catching projects. His firm’s latest is certainly no exception.

With 54 steel tree planters embedded in the sides of a six-story, 41,000-square-foot building, Guerrilla Development‘s Tree Farm, at Southeast Third Avenue and Morrison Street in Portland, is aptly named. It follows the firm’s colorful Fair-Haired Dumbbell near the east end of the Burnside Bridge.

鈥淜evin literally did a napkin sketch of this idea, which was a six-story building with essentially a cube in massing,鈥� said Ben Carr, project architect for Brett Schulz Architect PC. 鈥淎nd he handed it to me and said, 鈥楲et’s figure this out and get it done.’鈥�

From that initial drawing, the concept of a building adorned with living trees quickly came to life. Now general contractor Pro Teck Construction is building Tree Farm on a quarter-block parcel. It’s a constricted site, with only a few feet separating the new building from adjacent structures and the Morrison Bridge. This ruled out use of a tower crane, Pro Teck superintendent Michael Griffy said.

鈥淚t’s a great design, but it’s been a challenge, and it’s a unique challenge,鈥� he said. 鈥淚 would really like to be able to put a crane on the Morrison Bridge and stock the sixth floor from there.鈥�

The project is noteworthy in a number of ways, beginning with the work done below grade. There, deep soil mixing was employed to compensate for the soft fill soil found near the banks of the Willamette River. Columns 45 feet deep were placed in a grid pattern underneath the foundation. These are separate from bearing piles and are intended to stabilize the soil rather than the building itself.

鈥淚t’s basically a concrete slurry to stabilize the soil to prevent liquefaction in case of an earthquake,鈥� Carr said.

However, the biggest challenge was creating a design for load-bearing exterior walls. Architects worked with WDY Structural & Civil Engineers to devise a solution involving what Carr describes as a 鈥渟ort of exoskeleton of tube steel.鈥�

鈥淭he first thing they told me is you’re taking all of this weight, and each of those tree planters is going to weigh between (2,000 and) 3,000 pounds,鈥� Carr said. 鈥淎nd you’re putting all that weight on the outside of the building, which is a terrible seismic idea.鈥�

This exoskeleton, however, is designed so that it does not bear the weight of the surrounding wood-framed building itself. Instead, it will only support a series of steel knife plates welded into the columns. Those plates will then be the mounts upon which the steel planters will be placed.

鈥淚t’s essentially a separate column,鈥� Carr said. 鈥淭he tube steel carries the weight of the trees back into the building.鈥�

And because structural steel is already in place for the exterior walls, it was no stretch to include steel load-bearing columns on the first four stories. Exposed wood columns are featured on the top two floors, and glu-lam beams throughout so that a woodsy aesthetic is evident inside and out.

Cross-laminated timber panels were considered, Carr added, but rejected on cost and logistical grounds.

The building itself has a slab-on-grade foundation and five stories of wood framing. It will hold office space above ground-floor retail space.

One more challenge was ensuring the strawberry trees destined for the planters will receive enough water. Rainfall alone is not enough to support the small, evergreen trees, which are native to Western Europe and the Mediterranean region. So, designers worked with Cistus Nursery to devise a network of irrigation piping to be built into the wood-framed walls and plumbed to provide water to each individual planter.

Each of the building’s four exposures is controlled by separate valves. Each story is similarly controlled, all the way down to individual planters, which will have separate irrigation lines attached to a moisture sensor to measure the amount of water received from all sources.

鈥淲e even have the ability to fertilize and water each tree remotely without actually getting up on the building,鈥� Carr said.

Crews have nearly roughed in the building. Drywall is being installed drywall throughout. MEP contractors, meanwhile, are busy building mechanical systems. Project delivery is scheduled for this fall.

Editor’s Note: This story has been updated to reflect both the correct number of tree planters on the building and the anticipated time of project delivery.