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In Portland’s Goose Hollow neighborhood, crews are already in deep working on what will be a 21-story mixed-use building.

Andersen Construction is building the Alta Art Tower for developer Wood Partners on a half-block site at 1516 S.W. Alder St., adjacent to the Artists Repertory Theatre. Ankrom Moisan Architects designed the building to hold 314 apartment units over ground-floor commercial space. Four stories of below-grade parking will be included as well.

A unique lobby space will include a performance stage and art gallery. Other amenities will include a rooftop club room with two outdoor terraces, co-working and meeting space, and a fitness studio. The apartments will feature quartz kitchen countertops, stainless-steel Energy Star appliances, gas ranges, vinyl-wood flooring, master bathrooms en suite and more.

The Portland Design Commission approved plans in December 2018 and ground was broken in July 2019.

鈥淭he existing lot contained an L-shaped building 鈥� a portion was demolished to make room for the Art Tower apartment building,鈥� said Eric Sprague, a senior project manager with Andersen Construction. 鈥淎nd now we’re in the process of excavation activities, going down four stories before we’ll get back up to grade, and then we’ll go 21 levels up.鈥�

In many respects the Alta Art Tower will be a fairly conventional high-rise structure. Above grade, the building will have post-tensioned concrete decks and columns. Pile drivers and operating engineers with Pacific Foundation are drilling tiebacks and building lagging walls for the below-grade parking, while excavation work is being done by Westech Construction.

Plans call for use of prefabricated wall panels with brick masonry cladding manufactured by subcontractor Western Partitions Inc. It’s an arrangement similar to the one being used by Andersen Construction for a high-rise at Southwest First Avenue and Columbia Street.

鈥淎ndersen is the regional pioneer in fully prefabricated exterior systems,鈥� Sprague said. 鈥淎rt Tower is another example of leveraging multiple prefabricated systems to create an efficiency, both in the shop and in the field, and to minimize costs for our clients. There is a substantial dollar savings to not having any type of exterior scaffolding, as well as eliminating a separate trade to install the brick cladding.鈥�

The prefabricated panels will be set from the inside of the building by a team of Western Partitions Inc. carpenters.

鈥淭he panels will be staged and set from the floor, utilizing a small crane from the floor above to lift and swing them into place,鈥� Sprague said. 鈥淭his process allows the tower crane to remain focused on the structure, and yet the exterior progress will follow right behind the shoring removal. We have been working closely with the subcontractors and design team to detail connections and transitions for a watertight assembly that omits sealants being placed from the exterior, as we wanted to come up with a way where everything could be set from the inside.鈥�

Another unique aspect of this project is not actually on-site: A full two-story mockup is being used to test the exterior wall panels to ensure quality and fit. Much effort is being invested in quality control and assurance prior to the first panel being shipped to the jobsite.

鈥淭he panels have to be fabricated correctly, because we have very limited options if they show up on site and something isn’t correct,鈥� Andersen Construction project superintendent Glenn Whitefield said. 鈥淭his is why we focus so much attention to the pre-planning and the mock-up process.鈥�

Sprague added: 鈥淪pecific to Art Tower exterior, we are approaching near a thousand framed panels for this project and can’t afford to have them built incorrectly, or be unsure of how the transition between the framed panels and window wall system will tie together.鈥�

This includes WRB (weather resistive barrier) membranes, metal flashings, attachments to post-tensioned concrete decks and more. The full-scale mock-up provides the team an opportunity to review, test and make adjustments as needed 鈥� prior to the start of full production.

鈥淚n addition to an exterior mock-up, we’ll be doing a full interior mock-up in the basement for a few purposes,鈥� Sprague said. 鈥淚t will ensure that the sequencing and fit and finish of the materials will work, to provide owner and the design team an opportunity to make any adjustments to the product selection and to establish the expected level of quality that can be replicated in the field. There’s a heavy emphasis here on making sure that this is a great plan.鈥�

Once the project is completed, Andersen Construction plans to explore the possibility of converting the mock-up into a full tiny home for donation to the Kenton Women’s Village in North Portland.

鈥淲hatever we can salvage to use or don’t have to throw away we’re good with,鈥� Whitefield said.