Skidmore, Owings & Merrill

Chicago, Illinois

After the Ledge at Skydeck Chicago at the Willis Tower opened in 2009, attendance rose from 1.09 million in 2008 to a projected 1.4 million for 2011.

Before you go to the Ledge at Skydeck Chicago at the Willis Tower (formerly the Sears Tower), you may want to get in the mood by seeing Vertigo (1958), Alfred Hitchcock’s famous thriller. Or maybe not. The thrill, panic, and fear so memorably portrayed in the film is present in real life at the Ledge. Skidmore, Owings & Merrill (SOM), which designed the tower in 1973, came up with these subtle additions to a renovated Skydeck when the new owner wanted to revamp its image after the tower’s name change. SOM and engineer Halcrow Yolles created four five-sided glass balconies about 4 feet deep, 10 feet high, and 10 feet wide. They are formed by laminating three layers of 1⁄2-inch clear, no-iron, specially coated glass panels and mounting them on steel frames. The assembly slides on rails so the outdoor glass rooms can be retracted into the building for maintenance. The frames’ hollow tubes bring conditioned air to the ledges and provide air flow to mitigate condensation. Needless to say, the scheme has been wildly popular. The renovation of Skydeck and the addition of the Ledge have upped attendance from just over from 1.09 million in 2008 (before its completion in 2009) to a projected 1.4 million by the end of 2011. While the 3,500-square-foot multimillion-dollar renovation is not cheap, the building owner, U.S. Equities Realty, expects income and attendance to keep soaring. 

Skidmore, Owings & Merrill LLP
224 South Michigan Ave., Suite 1000
Chicago, IL 60604
P: 312.554.9090
F: 312.244.3056

Chicago, Illinois

Completion Date:
July 2009

Gross square footage:
3,500 sq.ft.


Owner: US Equities Realty, Randy Stancik, 312.875.2423

Skidmore, Owings & Merrill LLP
224 South Michigan Ave., Suite 1000
Chicago, IL 60604
P: 312.554.9090
F: 312.244.3056

Personnel in architect's firm who should receive specialcredit:
Thomas Kerwin, FAIA, Managing Partner
Ross Wimer, FAIA, Design Partner
William Baker, Structural Partner
Charles Hasbrouck, AIA, Project Manager
Darren McKinnon, Project Manger
Aaron Jensen, AIA, Senior Design Architect
Peter Freiberg, AIA, Senior Technical Coordinator
Dane Rankin, Senior Structural Engineer
Sonja Janecek, Design Architect
Weiqi Wang, Design Architect  
Gabe Wong, AIA, Technical Coordinator
Henry Lee, Technical Coordinator
Juan Carrion, Structural Engineer

Architect of record: Skidmore, Owings & Merrill LLP, Ross Wimer, 312.360.4038

Structural Engineer(s)
For Fixed Interior Elements
Skidmore, Owings & Merrill LLP, Dane Rankin, 312.360.4102

For Observation Box
Halcrow Yolles, Terry McDonnell, 312.212.4205

Environmental Systems Design, James Johnson, 312.456.2319

Schuler Shook, Inc., 312.944.8230

Glass/Architectural Metal Contractor:
MTH Industries, 708.498.1100

General contractor
Berglund Construction Company, Tom Brooks, 771.374.1000

Contact: Randy Stancik/Skydeck Chicago, 312.875.2423
Credits: © Skydeck Chicago

Credits: ©SOM or SOM | ©ImageFiction

CAD system, project management, or other software used:
AutoCAD and 3D Studio Max



Structural system
Structural steel wide flange beams for the fixed interior elements, structural steel tubes for the observation box.

Structural glass walls and roof: Laminated (3 layer), fully tempered with PVB interlayers.

Structural glass floor:  Laminated (3 layer), fully tempered with Sentryglass Plus interlayers.