SOM-designed The Ledge in Chicago cracks under visitors feet


The protective coating for the glass viewing deck on the Willis Tower in Chicago had cracked, leading to temporary closure.

Following the reports of a crack, the four box viewing areas of The Ledge attraction were temporarily closed for a morning routine.

A spokesperson for the building explained that there was no danger in the crack and that it was only a layer of protective coating over the structural glass designed to prevent the glass from damaging or scratching.


“This coating does not affect the structural integrity of The Ledge in any way. Occasionally, the coating will crack, as it is designed to in order to protect the surface of the glass,” said Brian Rehme, a spokesman from public relations firm FleishmanHillard.

The Ledge was designed by Skidmore, Owings & Merrill with structural glass designers Halcrow Yolles and opened in 2009 as an addition to the tower’s existing 1974 sky deck.

Made from three layers of 12mm thick tempered glass laminated together, each panel used in the boxes weighs over 680 kilos. The boxes can retract into the building for cleaning and maintenance.

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