Just who deserves the credit for initially suggesting that the Rookery’s lightcourt’s detailing be used on the exterior of the Tacoma Building has never been resolved. I tend to favor the building’s contractor, George Fuller, who, not so coincidentally, was the contractor of the Rookery. The timing would seem to confirm my suspicions as it would have been very cost-effective for Fuller to simply move his now experienced crews from where they were wrapping up the job on the Rookery two blocks north to begin construction on the Tacoma.
Root had modeled the Rookery’s courtyard from George Post’s pioneering use of iron framing in the lightcourts of New York’s Equitable Building (1867) and the New York Produce Exchange (1881). Quite frankly, as I review the dates of George Fuller’s early career, it is plausible that he may also have played a role in transferring Post’s technology to Chicago. I have already shown that Root always kept abreast (and would continue throughout his short career) of the latest developments in New York construction. For instance, before he moved to Chicago in 1872, he was practicing in New York during the construction of the Equitable Building. Meanwhile, Fuller was in New York erecting the Untied Bank Building during the same period Post’s Produce Exchange was under construction. Historically, George Post should be recognized as the first American architect to employ the iron skeleton frame in the exterior of a tall building. Root’s achievement was the first use of such technology in a Chicago building. (I repeat, and will continue to do so, throughout this blog, New York, and not Chicago, was the birthplace of the iron skeleton frame.)
Sooner or later, some architect would be the first to put Root’s Rookery lightcourt’s iron frame and curtainwall on the outside of a building. I have surmised that Root, himself, may have been the first to do so in the Midland Hotel in Kansas City. The first confirmed application on the exterior appears to have been Holabird & Roche in the Tacoma Building. For this reason, as the topic of what building was the first “skyscraper” became a subject of continuous debate among architectural historians in the 1920s, while many historians favored Jenney’s Home Insurance Building, other early histories of Chicago’s architecture argued that this honor belonged to the Tacoma Building, Some historians who championed the Home Insurance Building, attempted to trace Holabird & Roche’s structural detailing back to the Home Insurance Building, if for no other reason than they believed that the two partners were employed in Jenney’s office during the design and construction of the Home Insurance Building. Later research has proven not only that they both had left Jenney’s office prior to the commission for the Home Insurance Building, but also as I will review, their detailing followed not Jenney’s, but Root’s structure in the Rookery. Jenney’s detailing had elicited little professional interest during its construction (as we have already seen, no one copied his details) and its conventional construction generated no public interest. Quite the contrary happened once construction of the Tacoma began; police had to called to the northeast corner of La Salle and Madison to control the throng of “sidewalk gawkers.”
Root’s detailing in the Rookery was a logical first step toward the use of iron skeleton framing in skyscrapers (as was George Post’s in the Produce Exchange) because the Rookery’s massive masonry exterior walls would more than adequately brace the building against the city’s significant wind loads. This meant that he did not have to impart a significant amount of lateral rigidity to the iron framing in the lightcourt. We have already examined Bradford Gilbert’s solution to the wind loads in the thin sliver of the 11-story Tower Building in the diagonal bracing that he had detailed in each bay. Trying to erect a much larger footprint, to a height even greater than eleven floors would pose a greater challenge, and one that demanded of its builders the ultimate level of respect for the nature of this challenge. Only a fool would try to “do everything at once” in constructing a large 12-story building with an untested, experimental structural system. And so, builders of the iron frame would slowly, and carefully, shed those heavy, rigid, masonry bearing walls, one wall at a time, as buildings grew taller and taller.
Bruegmann’s research had uncovered Roche’s diary in which he jotted brief summaries of the day’s events. After Walker had stopped excavation upon having succeeded in buying the adjacent lot to the north and had sent Holabird & Roche literally back to the drawing board to design a larger building for the expanded site, Roche recorded in his diary on March 8, 1888, that elevator manufacturer William E. Hale had suggested that the planned building should consist of a conventional masonry bearing exterior with a double-loaded corridor plan that wrapped around the corner, leaving the northeast corner of the site open as a light court. The architects, along with Fuller and their consulting engineers, Charles G. Wade and Corydon T. Purdy, had compared the cost of this scheme against that of a much thinner, Rookery-like iron frame and curtain wall exterior, calculating that the extra rental floor area gained with the thinner curtain wall would generate $4500 a year more that would quickly offset its $10,000 higher construction cost. (We will hear about Purdy’s importance in later buildings. Corydon Tyler Purdy [1859-1944] was born in Grand Rapids, WI, studied Civil Engineering at the University of Wisconsin, and after having worked for a number of bridge design and construction firms, moved to Chicago in 1888, forming a partnership with Charles G. Wade.)
Two weeks later, March 23, Roche recorded that Walker himself had approved this alternative, that is, the building’s final configuration should consist of two masonry u-shaped shafts aligned at a right angle to each other with the two exterior streetfronts made with the Rookery’s lightcourt detailing of iron framing that supported the glass and terra cotta exterior enclosure. This scheme did not eliminate the heavy exterior masonry walls, it simply had rotated them 90° so they were perpendicular to the street. In other words, his plan had not eliminated any of the conventional masonry, it had simply relocated it from the exterior to the interior. In essence, this plan had simply turned the Rookery inside out. Walker, meanwhile, had added another floor to the ever-growing project, making it 13 stories tall, (probably as a response to Minneapolis’ Northwest Guaranty Building and Owing’s proposal to build his 13-story tower).
The increase in height demanded added caution with regards to the building’s ability to resist the increased wind loads because wind loads increase exponentially and not just linearly in relation to height. Not only does the amount of wind increase with the extra surface, but also the point at which the accumulated windload is applied, the length of the lever arm, grows farther from the ground, twice increasing the rotational force the building has to resist. I have used some basic numbers to illustrate the effect of increasing the height of a building below:
Fuller recommended that rivets be used wherever possible to connect the cast iron columns with the wrought iron and steel beams for speed of construction as well as for the extra rigidity to be gained in the connections. The wind-resisting structure was conceived, therefore, as a hybrid system that reinforced the riveted iron frame with the massive lateral masonry walls. One thing to remember, however, is that while Walker’s idea had opened up the exterior for a maximum of glass, it had not removed any of the heavy masonry. While this was good for the wind loads, Holabird & Roche would still have to design a foundation for a building that was going to be three floors higher (heavier) than the traditional soil strength limit of ten floors. Fuller responded with a relatively new technique. Soil borings had indicated the presence of a number of pockets of soft clay or water within the bearing strata. These were replaced with concrete that was pumped under pressure into these locations. (Despite these precautions, when the building was demolished in 1929, the building was found to be leaning 11 ¾” to the east.
Conceptually, the architects and engineers had turned the Rookery inside out. Nevertheless, for the first time, the iron frame was to be seen on the streets of Chicago (for the construction of the Rookery’s lightcourt had been hidden from the public by its massive masonry exterior), and the Inter-Ocean immediately had appreciated the revolutionary nature of the Tacoma’s exterior cladding: “its skeleton as it were – fireproofing tile will be used with such completeness that not a vestige of iron will be seen anywhere. A new order of architecture [my emphasis] is evidently here, and coming to stay – iron and fireproofing.” As early as 1888, the reporter from the Inter-Ocean had identified the Chicago School language.
The Tacoma Building was not just “a new order of architecture,” but was also revolutionary in its construction process. So much so that a company of policemen had to be assigned to the construction site for crowd control, as people were flocking to the site to see for themselves what rumor had called “floating brick.” Floating brick was a result of Fuller’s realization that as the masonry curtain wall was no longer a continuous brick wall from the ground up, but a series of brick partitions that were constructed on the iron frame. Therefore, it would be faster and less expensive, that if instead of having his bricklaying crew start the brick exterior at the ground and proceed upwards, he had three separate teams that would start laying brick at three different floors at the same time. In order for this to proceed, Fuller had to have erected all thirteen stories of iron framing around the building’s exterior perimeter, in conjunction with the four masonry bearing walls, before letting his three crews of masons start placing the exterior’s brick and terra cotta. By all rights, this should have been the first time this was done in Chicago, if not the country, (i.e., the entire iron frame erected on a building’s exterior before it was clothed) and would have added to the public’s perception of the radical nature of this building.
In fact, as we will examine in the next section, Holabird & Roche had taken advantage of this system to completely open up the ground floor: there was only glass and what little metal needed to frame it along the sidewalk. The result of these decisions was that the three crews were laying brick on three different upper floors (second, sixth, and tenth) that had no contact with the ground, hence, to eyes that had become accustomed to seeing brick walls grow from the ground up, the brick in the upper floors did, indeed, appear to “float.”
Not everybody was convinced, however, that such a radical departure from conventional construction would generate a safe building. So much concern was raised, in fact, that the Inter-Ocean took the unusual step of interviewing Building Commissioner W. J. Edbrooke about concerns that people had raised about the Tacoma’s overall strength:
“Reporter: On the score of strength and height you made no objections?
“Edbrooke: No, none whatever. The inside and alley walls – or the principal supports – are very heavy and very strong. Then the foundation, the shape of the building on the ground makes it self-supporting to a great extent, while the floors are essentially iron and steel. The floors are so braced laterally as to make the structure simply a tower of iron… Every connecting part is riveted and bolted and braced together in a manner unknown in mere masonry. While externally it looks to be all brick and terra cotta, all this is in reality mere sheathing of an iron tower. Inside, every steel pier, between the windows, are massed, vertically and horizontally, these iron and steel supporters, braced and riveted together in all directions… Certainly there can be nothing stronger than such an iron constructed building.”
FURTHER READING:
Bruegmann, Robert. The Architects and the City: Holabird and Roche of Chicago, 1880-1918. Chicago: University of Chicago Press, 1997.
(If you have any questions or suggestions, please feel free to eMail me at: thearchitectureprofessor@gmail.com)
The Architecture Professor 