Ever since the Sears Tower was eclipsed as the tallest building in the world, from time to time somebody in Chicago would float the idea of reclaiming the title, but the talk never went anywhere because of the impracticalities of building very tall structures. Besides, tall buildings are terrorist bait. Now all of the sudden Chicago has three so-called supertall buildings under construction. Blair Kamin has an excellent primer explaining why very tall buildings have become feasible--structurally, if not economically.
All three supertalls under construction in Chicago--the Trump Tower, Waterview Tower (say that three times quickly without saying "Water Tower Place"), and the Chicago Spire--are all located on impossibly small lots. Trump has crammed himself between Mies' elegant IBM building and the iconic Wrigley Building, while the Spire lot is about the size of a dog park. (In fact, I think that's what it was before they started building on it.) I walked by the Waterview Tower site the other day and I thought they were constructing a health club or something like that. I can't believe they're going to drop a 1,047-foot building in there. The new building technologies make taller, thinner buildings possible by using a technique resembling the old portal frame method of constructing skyscrapers, in which structural elements interlock across the building, rather than buttressing it from the outside, like the John Hancock Building.
The new supertalls are built around a central core, with arms extending out to columns on the perimeter of the building. This means everybody gets a window office, at least theoretically. It also means the elevators are snug and safe within the massive core of the building should anyone get any ideas. The core and outrigger method, as the new technology is known, allows engineers and architects to stack floors up until the money runs out.
Which brings me to the Chicago Spire. As I write the caissons are being drilled into the ground for Santiago Calatrava's 2,000-foot tower (photo above). However, just because the construction crew is drilling massive caissons into the muck doesn't mean the building will reach its intended height. The developer Garrett Kelleher won't start selling units in earnest until September. Considering the current glut of condos in the Chicago market--currently there are over 2,000 two- and three-bedroom condo units for sale in the city priced between $350K and $500K--it seems inconceivable that Kelleher will find buyers for another 1,200 units. Add to that the units for sale in the other two supertalls and it's a buyer's market for luxury condo units, to say the least.
While the technology behind the Chicago Spire will allow for a slender building, economic forces may leave us with a stump spire. Earlier designs messed with the building's central design motif: a very tall building with the small footprint, and Calatrava eventually restored the sculptural grace of the original design. Calatrava's avian aesthetic won't work with a conventionally proportioned building. Unless the Dublin-based developer can pull off a marketing miracle, Calatrava will have to redesign the building, and we may end up with just another ordinary skyline hog.