Like many American cities, Tacoma, Wash., has a complicated relationship with its parking garages. In the early 1970s, a suburban mall had lured retail anchor tenants away from the downtown area. In response, the city—hoping that ample parking would reverse the trend, encourage new development, and reactivate the urban core—cleared away entire blocks to make way for two imposing parking garages. Unfortunately, the tactic didn’t work as planned and the garages remained mostly vacant until downtown office space began filling up a decade later. The years of underutilization had taken their toll on the concrete monoliths; in the mid-2000s, the city discovered that the seismic post-tensioned cables in the Park Plaza South parking garage were rusting.
Projected revenue from the garages, which had become profitable for the city over time as commercial tenants began returning downtown, was used to underwrite the construction of the convention center one block away. As a result, the revenue stream had to continue regardless of whether it came from the garages in their existing location or from a new facility at another site. A development team comprising partners from local firms BLRB Architects and PCS Structural Solutions along with Puyallup, Wash.–based Absher Construction came up with a plan that would not only improve the urban landscape but also retain the existing south garage and leave half of the parking stalls available to continue generating revenue throughout construction.
“Although the seismic loads were compromised, the structural capacity of vertical loads was left intact,” says Ben Ferguson, project manager at BLRB and LEED administrator on the project. “We leveraged that to build three lightweight floors on top of the garage. Having a structural engineer on the development team inspired a lot of innovation.”
The project team’s plan would convert the parking garage into what would become the $35 million Pacific Plaza, a 250,000-square-foot mixed-use facility with 32,000 square feet of refurbished storefront office and retail space on the ground floor, four stories of parking, and 68,800 square feet of Class A office space.
To limit the amount of dead load that the new floors would add, as well as heighten visual interest to the building, the architects turned to metal. Castellated steel composed of fabricated beams with weight-reducing holes provide the lightweight structure for the upper stories while metal panels help form a new façade.
To reinforce the building seismically, the design team strategically located a new elevator and stair core through the center of the building and cast 5 inches of concrete on the exterior vertical surfaces along the garage's longitudinal elevations. They then removed 15 feet of the building from three of its four corners to release the tension in the failing post-tensioned cables.
The upgrades redefined the look of the building. Originally, the 300-foot-long structure contained eight columns 50 feet on center, making it look remarkably similar to an oversized, three-dimensional air grille. “Cutting the corners let us change the massing, and we added a second set of columns on 25-foot spacing to alter the rhythm of the building,” Ferguson says. “The new concrete exterior covered up the worn, serrated concrete finish, and we painted the texture a warm off-white to brighten it up.”
The mix of materials and architectural details strengthened the project’s presence and modernized Pacific Plaza. A “glass tower” through the building’s center creates daylit conference rooms on office levels, Ferguson says. On the elevation facing a major arterial road, limestone cladding rises up on the faÇade 30 feet above street level to create a high-end experience for pedestrians.
While the ends of the building's lower levels are clad with cement-composite rainscreen panels, the architects chose to clad the length of the top three levels—one new floor of parking and two stories of conditioned office space—in insulated metal panels to change the proportion of the building. Finished in a weathered-zinc paint color, the panels create the visual effect that the upper floors are suspended above the structure. And because the panels are capable of single-mitered corners, the potential for bulky connections at building corners was eliminated, creating a clean, flat façade.
Metal panels not only gave the mixed-use building a polished look, but also improved its energy efficiency. “The metal panel does a lot of work for us because it has an architectural-grade finish, but it’s also an industrial insulated panel at a very competitive price point,” Ferguson says. “We put a peel-and-stick air-and-vapor barrier on the building first, and then the insulated metal panel. This let us eliminate the dew point [from falling within the walls] … so no moisture and mold [would infiltrate or grow] … inside and created a very high-performance building envelope.”
A thermal study of the building showed that after two years of operation, the combination of the air-and-vapor barrier and the insulated metal panels, which are rated at R-23, is allowing the building to exceed its predicted 35 percent energy savings over baseline. For Pacific Plaza’s owners, the building’s performance translates to savings in anticipated expenses.
From a tenant perspective, the metal panels contribute to interior build-out flexibility. If tenants want to add power or data lines, for example, they don’t have to work around bulky wall insulation because it is installed on the building exterior.
Attention to Detail
Seattle-based Kenco Construction installed the more than 26,000 square feet of insulated metal panels, seamlessly interfacing them with the glass tower, cement-composite cladding, and rainscreen systems. Kenco president Ken MacDonald says that because the foam and metal panels arrive ready to install without requiring much field fabrication, much of his work takes place before the products made it to the jobsite.
“We create very detailed construction drawings to work out all the sizes and shapes, verify the dimensions, and make sure the systems’ details will mesh together before the panels get shipped,” he explains. “This means we need to clarify and confirm information with all the players—the designer, owner, and general contractor—in order for things to go smoothly in the field. This process also gives our field crew an accurate picture of what will happen on site.”
The 3-inch-thick panels arrived on site in 24-inch, 30-inch, and 36-inch widths. Because the project is located in a tight urban environment, workers had to sequence construction carefully. Because the panels were installed beginning at the fourth floor level, 28 feet high, and go up to 105 feet high, there was a limit to what workers could do by hand. The crew found creative ways to access the right locations through a combination of a boom, crane, lightweight hoists, and scaffolding.
Although the panels provide weatherproofing, thermal capacity, and durability once installed, the lightweight, fragile sandwiched foam assemblies had to be handled delicately beforehand. The crew took care not to drop them or drop anything on them during the installation process. An interlocking tongue and groove assembly connects the individual panels, which have a sealant strip and gasket inside their joints, and a clip assembly with a thermal break on the attachment.
“The joint assembly is really well tested and the panels are very reliable,” MacDonald says. “I’ve never had anyone call me back about a problem. They go up efficiently and with all the different characteristics from the smooth finish to thermal performance, you accomplish a lot with one product.”
Despite the current state of the economy, Pacific Plaza—Washington’s only LEED Platinum–certified core-and-shell project to date—is fully leased. “We’ve got a broad-range tenant mix and a full-service grocery store on the ground level, which is a critical amenity to encourage people to move downtown and fill up vacant condos,” Ferguson says. “The owners in this project are local and really want to make their city a great place to live. Pacific Plaza’s sustainable features—and the way the development is revitalizing this area of town—are making that happen.”
KJ Fields writes about architecture and sustainability from Portland, Ore.