This open timber pavilion with an overhanging roof was named the winning design of the Lakefront Kiosk Competition in 2015. Completed last October in Grant Park for the Chicago Architecture Biennial, Chicago Horizon has a square, flat canopy measuring 56 feet on each side—the maximum length of timber that can be legally carried by a truck.
The roof is the first point-supported, two-way slab structure to be built with timber, according to the design team members, Ultramoderne co-principals Aaron Forrest, AIA, and Yasmin Vobis, who are based in Providence, R.I., and structural engineer Brett Schneider, a senior associate at Guy Nordenson and Associates in New York.
The canopy consists of two plies of cross-laminated timber (CLT) panels laid crosswise to each other. The 14 panels, each 8 feet wide and 4.125 inches thick, are topped by a rubber waterproofing membrane and gravel ballast. Overall, the roof weighs around 135,000 pounds, nearly half of which is the CLT itself. The load of the roof slab is carried in perpendicular directions and bears directly on 13 glulam columns distributed in a radial pattern, as opposed to the typical beam-and-column grid. “The builders said, ‘Why didn’t you just do a frame?’” Schneider says. “We see two-way slabs in concrete everywhere, but in timber it’s very unusual.”
“They’re leveraging this material to its fullest potential,” juror Doug Stockman, AIA, said, “and then creating the forms, the space, and the shapes out of that.” Juror Elizabeth Whittaker, AIA, added, “This project masters an economy of means and material that is precisely and exquisitely detailed.”
The crucial pavilion details, according to the designers, are the column-to-ground connections, column-to-roof connections, roof perimeter, viewing aperture edges, and the chain link surrounding the stairs and kiosk. The team specified the configuration and angles of fasteners to maximize the roof span and to resist the shear forces of winds from Lake Michigan.
Visual intrigue was as much of a goal as technical prowess. Visitors can poke their heads through a portal in the roof by climbing the freestanding dual staircase-and-seating area, which terminates in a landing beneath the roof level. “When you go up the stairs, the roof becomes a plane to frame your vision of the horizon and the city,” Vobis says. On grade, the long side of each rectangular column is rotated to point in a different direction, guiding visitors’ gaze into the heart of the pavilion and back out to the horizon.
Juror Mic Patterson said, “This is a classic minimalist construction. The more you contemplate it, the more its subtle sensibilities draw you in.”
Project: Ultramoderne, Chicago
Client: Chicago Architecture Biennial, Chicago Park District
Design Firm: Ultramoderne, Providence, R.I. · Yasmin Vobis, Aaron Forrest, AIA, Emily Yen, Assoc. AIA, Tida Osotsapa, Will Gant, Hua Gao, Ronak Hingarh (project team)
Design Structural Engineer: Guy Nordenson and Associates · Brett Schneider
Structural Engineer of Record: Thornton Tomasetti
Architect of Record: Animate Architecture · Joe Lambke
Fabricator: Nordic Structures
Funding: BP; Chicago Park District; Chicago Architecture Biennial; Rhode Island School of Design; ReThink Wood; Nordic Structures
Photography: Naho Kubota
Special Thanks: Laura Briggs