Behind the Scenes with The Astor at The Washington Building

In our Q&A series, we take a candid look at projects, hearing from the engineers who bring them to life. In the latest round, Senior Structural Project Manager, Rebecca Hix Collins, shares insights from The Astor at The Washington Building. A recently completed historical renovation, The Astor honors its legacy while providing modern, boutique-style apartments in the heart of Tacoma.

Tell us a bit about the project.

The Astor is a seventeen-story, landmarked structure located next to the busiest part of downtown Tacoma. Formerly known as the Washington Building and constructed as a bank with offices above, we had the privilege of converting the building into apartments. The main building system consists of steel frames, and while not unusual for early 1900s East Coast skyscrapers, The Astor utilizes a floor-framing system not usually seen on the West Coast. Flat, hollow clay tile floors with concrete topping span between the building’s steel beams. Originally fireproofing technology for building partitions, hollow clay tile is a structural block made of open-cell terra cotta molded to encase steel columns or beams. We knew we were in for an adventure when we discovered that framing system!

What made this project different?

It was the hollow clay tile floors – they were so unusual! East Coast engineers have experience with them, but no other local engineering firms we asked have ever seen them here. These tiles presented challenges when designing anything that touched this floor system, compelling us to craft atypical details and posing unique puzzles for the contractor.

What are some unique features, and how did we support them?  

One of the most unique features is the almost column-free floor on Level Two. When we first saw it on the plans, we didn’t believe it. We decided it had to be a mistake and they didn’t bother drawing the columns. Then we saw a historic photograph of a five-foot-tall steel beam with someone standing on top of it and realized the plans were correct. The builders placed this giant, five-foot-deep steel beam across the width of the building to create a column-free floor and stacked the rest of the columns on top. While this large beam gave them a column-free floor, it also meant that most of the lateral system we would use for earthquake safety stopped above Level Two, without connecting to the foundations.

Our solution to provide the missing link was to install new perimeter braced frames at the lower levels to strengthen and connect the systems.

Do you have a favorite feature? Any engineering standouts?

I had a good time figuring out what to do with our giant beam. Seeing the iron work and what they accomplished in the early 1900s was amazing. Being able to use a lot of it in our renovation was very special. Unfortunately, the steel was covered during fireproofing, but I snapped a few photos beforehand (see bottom left).

Another standout was choosing to utilize viscous dampers (see bottom right). We found that the building had a system of riveted steel moment frames distributed throughout that were originally designed only for wind forces. While those moment frames didn’t meet the unique requirements of the City of Tacoma’s building code, they still had many positive features that we didn’t want to overlook.

By choosing a system of fluid viscous dampers, which are essentially giant shock absorbers, we were able to tune the response of the building to match the capacity of the historic moment frames. Utilizing this approach aligned with our philosophy of finding the positive features that already exist in a structure and tailoring our retrofits to fix only what is deficient in those systems. This avoids expensive retrofits, like shear walls or braced frames, that ignore the building’s latent capacity.

What was the biggest challenge the team faced?

One of the biggest challenges was the number of unknowns. At the beginning, we had only five sheets of incomplete drawings to determine if this building could 1) transition to apartments and 2) be upgraded for 21st century use.

When most of the original drawings are missing, you use every available means to explain how the building was constructed. Our team searched for photographs from local historical societies, the City of Tacoma, UW Archives, MOHAI, and the Tacoma Historical Society to understand the structure. The contractor also removed finishes to expose the steel framing connections.

Partial drawings provided valuable dimensions and enough certainty to understand the basic framing layout, but we were still missing a lot of details. This is where digging into historical photographs and records paid off.

For example, the photo featured to the left allowed us to see the column orientation, where the rivets were, and some of the foundation. Another showed that a portion of the steel moment frame system at the top of the building stopped just above Level Two.

It sounds like a treasure hunt! What did the team do with these finds?

Historic renovations are treasure hunts! One by one, documents and images fit together like a puzzle, producing answers for the team.

For example, when determining how to reinforce the cornice, a small drawing depicted steel in it, and a photograph of the ironworkers on the roof confirmed it. The photo showed layers of steel, hanging rods, and bolts. When calculations were submitted to the building department, we included that image as proof. A field investigation of the terra cotta performed by an envelope consultant also exposed a few bolts to confirm location and condition.

Tell us a bit about due diligence. Why did it serve this project well?

An evaluation conducted during the due diligence period determined the condition of the building for the owner. Following the preliminary seismic analysis, we chose braced frames and dampers for the seismic system. Once selected, our approach didn’t change. The due diligence process allowed us to preemptively gather enough information to hit the ground running when design kicked off. And as design progressed, we further refined our analysis to reduce the number of dampers.

The due diligence period also allowed us time to target what information was really needed. We reduced the number of surprises later by filling in those information gaps early. Discovering the hollow clay tile floor system early was huge.

We became historians in our own right, helping the owner, architect, contractor, and building department understand challenges associated with the infrastructure and solutions that would make the transformation successful.

What was one thing you learned during this process?

I learned a lot about older floor systems and more about riveted framing than I ever knew before. We collected a lot of historical documents about hollow clay tile floor systems that we’d be happy to share.

Anything else worth noting? 

We attached our foundations to the original bank vault still prominently featured in the building’s basement Lock & Key Lounge. The vault was converted into a speakeasy resident lounge, complete with a tasting room and dedicated wine storage. Not something you see every day!

Why did you like working on this project?

It’s a really beautiful building in a great location, and to see it repurposed as apartments is amazing. We also had such a great team to work with: Venture General Contracting, Parker Mackay Architects, and Unico Properties were excellent.

I liked working with _____ because…

Parker Mackay Architects. They were so friendly, and Don Mackay was even willing to be onsite to help expose finishes and determine options. And Venture General Contracting too, as they really worked hard to make sure everything was built correctly.

How does this project impact the city or its community?

The City of Tacoma is working to bring more after-hours life into their downtown core and preserve their history. Residences like The Astor are exactly what the city needs to attract people to the area.

What is it like to see the finished product?

It’s amazing to see a structure that retained so many historic elements being used in a modern fashion. There’s no better feeling than knowing we helped make a building and neighborhood better.

A few quick-fires:

  • One word to describe the project: Rewarding.
  • Project team member who needs a free lunch: Quinn Zorich at Venture General Contracting. He did such a great job getting all the information we needed and integrating a complicated design.
  • When visiting, the first thing I check out is: Before they were covered up, it was the construction around the giant beams. Finally seeing them exposed and connected to our braced frames was always something I looked forward to.
  • This project has the best: Views of downtown Tacoma, Commencement Bay, and Mt. Rainier.
  • Next up, I can’t wait to design: Inspired by The Astor, I’d love to convert a building in Downtown Seattle’s Historic District to residences.

The Astor at the Washington Park Building was recently awarded NAIOP’s 2022 Historic Renovation of the Year.

Go behind the scenes with some of our other favorite projects: WWU Interdisciplinary Sciences Building, The Lodge at Saint Edward State ParkThe Little School Rivers Building, and Mount Si High School.

Project Team: Owner: Unico Properties / Architect: Parker Mackay Architects  / General Contractor: Venture General Contracting / Civil Engineer: AHBL / Geotechnical Engineer: GeoEngineers / Mechanical Engineer: Emerald Aire / Electrical Engineer: Tres West Engineers /  Acoustic Consultant: The Greenbusch Group / Historic Preservation Consultant: Northwest Vernacular

Images © WILL GOOD / J2G Creative

Historic Images © Northwest Room at The Tacoma Public Library, BU10759, BU10758, BU10756, BU10752