February 5, 2010 § 1 Comment
One of the more bizarre skyscrapers in Chicago is the “pencil thin” Mather Tower on Wacker Drive. Alonzo Mather had made a fortune by designing a more humane rail car for livestock, and invested in a small lot at 320 N. Michigan in the early 1920s. In the overheating real estate market of the mid-decade, he purchased a similarly sized lot fronting on the new Wacker Drive, and announced plans for twin towers–one on each lot–to frame Alfred Alschuler’s London Guarantee Building (that’s it to the left in the photo). With newly relaxed height limits, Mather was limited only by volume and setbacks, and his architect, Herbert Hugh Riddle, was able to exploit the zoning code’s nuances and proposed a 521-foot tower on a site that measured only 65 x 100 feet.
The structural and logistical gymnastics required to achieve this height were formidable. Riddle, a residential architect who had never designed a tower before, did his best, but was left with a tapering profile that, at the top, provided less than 400 sq. ft. per floor after space for elevators and stairs were taken out. Worse, the constant setbacks required by the zoning code meant that structural columns needed to be offset multiple times, creating large shear stresses that needed deep, cantilevered beams. The tower was so thin, in fact, that calculations revealed a very real danger that the structure could topple over in a wind storm, meaning that the foundations had to be designed not only to carry the building’s gravity load, but also to hold it down against uplift caused by wind.
Not surprisingly, the second tower never got built. Mather Tower, finished in 1928, never earned its $2.6 million construction cost back for its owner, whose estate finally sold it in 1945 for a mere $600,000. Its tower was popular with artists, many of whom rented the small floor plates as studios with world-beating view. The lower block is now a hotel that looks out on the equally slender Trump Tower, across the Chicago River.