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Cass Gilbert's Woolworth Building

Cassions and the Foundation of the Woolworth Building

Engineering the foundations for the site chosen for the Woolworth Building would prove to be difficult. Barr states that “the first skyscrapers were constructed in perhaps the geologically worst places for a skyscraper—along the bedrock valley itself—in particular with the Woolworth Building and the Municipal Building around City Hall.”[1] Yet, this did not detract from the success of the building. For the area around the Woolworth Building, bedrock averaged 115 feet below the surface with a range of 100 to 120 feet, and the mean water level was 35 feet below the surface, making pneumatic caissons necessary.[2] Nearly 80% of the workers who applied to work in these caissons were turned away due to being unfit for the work, and a full time physician and nurse were present to ensure safety.[3] In total, 69 caissons were sunk to support the Woolworth Building.[4] Foundation costs ended up being roughly $1 million, with the building costing $7 million, and land costing $5 million; this puts the foundation at 12.5% of construction costs or 7.7% of total costs, well within the expected range calculated by Barr despite the large number of caissons and excessively deep bedrock.[5]



More problems were faced when scope changes were necessary. Gunvald Aus entered a formal contract with Gilbert as structural engineer on September 23, 1910.[6] By November 4, workers had begun excavating Broadway and Park Place with pneumatic caissons (Figure 5) and on November 21, the Bureau of Buildings of the Borough of Manhattan issued the first construction permit for the project.[7] At this point in time, however, the working design was not quite what is currently standing. On January 19, 1911 Gilbert had to order the Foundation Company to stop work on the concrete pier footings due to an expansion and redesign once the Barclay Street corner had been acquired.[8] Woolworth had always wanted that corner but had encountered difficulties in purchasing it for a price that fit his master plan. The Hamilton family that owned the corner parcel finally conceded it to Woolworth as they feared losing the income producing value of their property to the shadow of the Woolworth Building.[9] After this purchase, the tower was moved from the corner of the site to the center so columns were moved accordingly. This resulted in new caissons being rearranged, and in some places, two caissons were used instead of one large caisson with heavy triple girders spanning both caissons to support the redesigned columns that no longer aligned exactly with the caissons.[10]
 
Along with the redesign, due to laws governing property lines, the caissons along Barclay and Broadway had to be narrower so they did not enter property Woolworth did not own despite being underground; this required very expensive and heavy girders to distribute the load.[11]
 
[1] Jason Barr, Building the Skyline (New York: Oxford University Press, 2016), 224.
[2] Sarah Landau and Carl Condit, Rise of the New York Skyscraper 1865-1913 (New Haven and London: Yale University Press, 1996), 384.
[3] Gail Fenske, The Skyscraper and the City: The Woolworth Building and the Making of Modern New York (Chicago: The University of Chicago Press, 2008), 191.
[4] Landau and Condit, Rise of the New York Skyscraper, 384.
[5] Barr, Building the Skyline, 221.
[6] Fenske, The Skyscraper and the City, 144.
[7] Ibid, 149.
[8] Ibid, 152.
[9] Ibid.
[10] “Frame and Windbracing of Woolworth Building,” Engineering News-Record 72, no. 5 (1914): 233.
[11] Gunvald Aus, “Engineering Design of the Woolworth Building Cass Gilbert, F.A.I.A., Archictect,” The American Architect 103, no. 1944 (1913): 164.

Kenneth Frye

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