Seattle’s new convention center is unusually tall

The six-story building’s novel approach was as much about utilizing a rare and compact downtown site as staying competitive. “Seattle turned away millions of dollars of convention business every year because they didn’t have enough space,” says Mark Reddington, a partner at LMN Architects. “Finding available space to expand in the traditional convention center format, meaning a big horizontal building, just didn’t work. It was impossible.”

Adapting the convention center model to fit the site resulted in a number of unique design opportunities.

The expansion, called the Summit building, is also a mixed-use development, with a 540,000-square-foot office building currently under construction on site, space for a planned 400-unit residential tower, 36,000 square feet of street-level retail, and 16,000 square feet of public open space.

Part of the project’s site juts over Interstate 5, which slices through downtown Seattle. With every square foot of space needed, the building had to use its full footprint. “We had to design a building that is partly cantilevering over the interstate lanes there, which just adds to the complexity of building a stacked convention center,” says Leonardo da Costa, a principal at LMN Architects.

One signature element of the design is the large staircase that steps up one side of the building. The architects call it a “hill climb,” and it creates an internal connection to every floor in the building as well as gathering and seating spaces on its window-lined edge. Due to an odd quirk of the property line realignment required by the construction of the interstate, the property line actually goes not just to the edge of the sidewalk but to the edge of the curb, meaning the building could technically take over the sidewalk. The architects chose not to sacrifice the ground level street life. “Pedestrian continuity is really important, ” Reddington says. At higher levels the hill climb does hang over the sidewalk below. Mirrored treatment on its underside creates a surreal connection between the street level and the building towering directly overhead.

The building was intended to line up with the streets, alleys, and landmarks of the neighborhood, including a roof terrace overlooking the historic Paramount Theater across the street. This is most striking at the top of the stairs, which peers out along 9th Avenue, with the Pike Place Market sign and Elliott Bay in the background. “You have this framed view that looks all the way down through the heart of downtown,” says Reddington.

Reclaimed wood is used throughout the project, including more than 10,000 comblike teeth on the ceiling of the lobby. The wood for other parts of the project came from a Honda dealership that once stood on the convention center’s site.

Reclaimed wood was also used on the ceiling treatment in the publicly accessible street level lounge space, which has an elaborate 180-foot-long wooden chandelier. Interspersed in this display are shade-like pieces that have been laser cut to shine the cell structure of Pacific Northwest trees onto the carpet below.

Even more reclaimed wood fills the ceiling space in the large ballroom on the convention center’s sixth floor. Made of decommissioned log booms used by the logging industry to corral timber floated in the region’s waterways, the planks show the tunneled paths where mollusks ate through the wood during its many years in the water. The room itself is also a feat, covering more than 58,000 square feet, or more than the size of a football field. “We’ve joked about playing a flag football game with the contractor there,” says Reddington.