Site, Materials, and Form Flow Together in Studio Gang’s Aqua Tower

by Zach Mortice
Associate Editor

How do you . . . design a skyscraper through a contextually mediated process that still manages to be expressive architecture?

Summary: Though aesthetically vivid and sculptural, Aqua Tower’s form was created through a structured, systematic process of addressing site constraints. Its composition method expresses architect Jeanne Gang’s nuanced interpretations of material honesty and construction methodologies.

Jeanne Gang, AIA, began the design of Aqua Tower in Chicago with a simple question of Miesian material honesty: How best to express outwardly the building’s internal structural skeleton—a conventional system of columns and slabs of reinforced concrete?

“I always start with materials,” she says. “What is this going to be made of?”

But by reveling in the individual personalities of her materials and rigorously working through site constraints and design goals, she and her firm Studio Gang Architects arrived at a form that delicately balances austere, Modernist expression with freehand form-giving. Her glass and concrete terraced tower promises to be one of the most eye-catching skyscrapers in recent memory in Chicago, the city that gave birth to the form. The 82-story, residential and hotel tower should be no less memorable for Gang herself. It’s the first time she’s worked with commercial real-estate developers, her first high rise, and likely the first skyscraper to be authored so completely by a woman.

Liquid stone
Gang’s tower, currently under construction and expected to be completed in early 2010, sits on a two-story base. Its massing is largely rectilinear and by-the-book: straight floor-to-ceiling glass curtain walls with an underlying concrete structure. But each floor slab extends up to 12 feet beyond the façade of the building to form terraced balconies on each floor that reach out and recede in waves and ripples of poured-in-place concrete—hence the marketing moniker “Aqua.”

The tower is owned by Magellan Development, and Gang’s firm is working with Lowenberg Associates, the architect of record. The 1.9 million-square-foot tower will have 228,000 square feet of hotel rooms at its base, 485,000 square feet of rental residence units on the middle floors, and 390,000 square feet of for-sale condominiums at the top. The skyscraper’s base is clad in handmade cementitious plaster, and its ground level contains retail space, a hotel ballroom, and a restaurant. Its second floor will be used for commercial office space, topped by a green roof complete with lounge space, pool, and running track. The tower’s main entrance sits under a curved and cantilevered upturned lip, all modeled after the smaller terraced balconies that hang above the base.

Site by site, constraint by constraint
The shape of the building’s balconies, its signature feature, comes primarily from contextual responses rather than aesthetic impulses. Gang started the design of the glass-walled building in downtown Chicago a few blocks from Lake Michigan and the Chicago River with a decision to extend the volume of the building outward in a handful of places to provide better views—to “bump out,” as she says, areas across several floors to see through the thicket of high rises in the city.

As with much of Chicago-based Studio Gang Architects’ body of work, sustainability is a primary design focus, so Gang and her team refined the terrace extensions to maximize solar shading. Sustainable features also will include rainwater collection systems and energy-efficient lighting. The green roof on top of the tower base will be the biggest in Chicago, Gang says. The tower will seek LEED certification.

Next, Studio Gang adjusted the floor slab extensions to accommodate individual unit floor plans. The most aesthetically driven part of the process came last: blending the terraces together to form smooth liquid transitions between and across floors. In the end, each floor has a unique set of terraces.

Long on contextual restraints
For a building with such a strong sculptural presence, Gang’s method is short on auteurship and longer on externally mediated contextual constraints, but she says this is an apt example of how she works.

“For me, that is design,” Gang says. “It’s not about drawing a cartoon icon. It’s about the coordination and choreography of taking all these restraints and criteria and orchestrating a form from that.

“I was interested in making a topographic, specific high-rise, as opposed to a universal, iconic high-rise. It’s interesting how this building related specifically to this site. If you did it again somewhere else, it would be different because there would be different things to relate to.”

Gang isn’t talking about general platitudes of adjacent building stock, history, demographics, and economy. Aqua Tower’s every arc and curve of its terraces is an explicit reaction to the forms that surround it.

Each terrace is an extension of the 9-inch concrete floor slabs, which taper to 6 inches at the balconies’ edge. They were all poured in place on top of a table system and shaped by a flexible steel edge that can be reused to make different shapes. Gang and the tower’s builders are using a robotic survey tool that is able to load construction drawings and lay them out almost instantly. “At first, we were thinking they were going to come within a tolerance of 4-5 inches, but it’s really dead on,” she says. “We’ve found that there’s no variation between what was drawn and what gets laid out.”

Gang says this digital efficiency helped her stay on budget with the project’s developer, saving time and money for extra materials. The tower’s unique design brought Gang and her team another money-saving bonus. They found that they could save over a million dollars by forgoing the building’s sway dampening system, because the parallel terraces diffused horizontal wind loads.

Mineral construction
Though it began with a question of material honesty, the concrete slabs of Aqua Tower subtly evoke another rock: richly stratified bands of coastal limestone outcroppings that shape the rural Great Lake region. Gang says she sees a shared set of natural forces that have formed both her concrete and native limestone formations: pressure, water, erosion.

“It’s the same with the Aqua Tower. It’s an organic process,” she says—revealing a deep understanding of the material composition and construction that binds manmade and natural materials in their most irreducible elements.