spandrel walls and the 1950 Chicago code

I’ve been sitting on this one for just a bit, but having shown off the latest in archival crate-digging to South Dakota State students earlier this week, I think I can roll this out now. (Shout-out to Jessica Garcia-Fritz and Federico Garcia-Lammers, who invited me to speak to their class. They’ve been studying the role of less-celebrated documents–specifications in particular–in the design and construction process–a brilliant piece of pedagogy and a research agenda that’s already paid dividends in terms of understanding how firms like the Guastavino Family actually did business…)

Two years ago I gave a short paper on the difficult passage of Chicago’s 1950 building code, one of the first ‘performance codes’ in the country. It replaced a traditional ‘prescriptive’ code that specified exactly what materials and configuration had to be deployed to meet various fireproofing requirements–so, instead of simply requiring a ‘one-hour’ wall, which modern codes do today, older codes would tell architects and builders to provide, say, a four-inch thick plaster-on-lath wall, or a single-wyth brick wall, etc., etc. Developers of single-family homes and skyscrapers both lobbied for the new approach, since the older code philosophy made it difficult to keep up with innovation–any new material had to pass not only technical advisors, but the entire city council, and many in Chicago (and Washington, which after WWII was working feverishly to address a growing crisis in housing) worked hard to pass more progressive codes that put the burden of approval on independent labs and manufacturers, rather than on political bodies like city councils.

The story of gypsum drywall in all this has been the most illustrative–and I’m happy to say that story (which involves aldermanic corruption and a fistfight on the floor of Chicago’s City Council) will be presented at an upcoming Construction History Congress (fingers crossed). But another aspect of the code change sheds important light on the development of the glass curtain wall in the city, and is of interest for the timing of its implementation–and the construction of one of Chicago’s most iconic high-rises.

Above are excerpts from the 1941 edition of the Chicago Building Code–the final major publication before the change that was approved in 1950. These passages refer to commercial buildings in the central business district, and you can see that they’re textbook ‘prescriptive’ provisions–you have to build the frame out of metal, concrete, or masonry, for instance, and you have a pretty limited palette of materials and configurations that you’re allowed to use where certain fire resistances are required. It’s that last passage, though, that I’m interested in–the requirement for a ‘spandrel wall’ of two-hour fire-resistive construction extending for three feet or more from window to window in any ‘non-combustible’ wall. Two hours is a serious level of fire resistance, met only with brick or concrete. The purpose was to prevent fire from spreading, floor-to-floor, through windows, a legitimate concern but one that was proving less and less valid as a growing body of knowledge about fire spread and suppression led to better and better sprinkler and alarm systems and exiting strategies.

Field Building, Chicago. Graham, Anderson, Probst, and White, 1934.

If you were designing a solid-skinned curtain wall like, say, the Palmolive (1929) or Field Building (1934), this provision made perfect sense–above each floor, you’d simply build a short brick wall that matched the sill height, which you were probably going to do anyway since the formula for building skins at the time was, typically, solid panels with intermittent windows–the code, like many codes, simply followed general practice.

Lever House, NYC. Gordon Bunshaft/SOM, 1951. Digital reconstruction by Saranya Panchaseelan, Paolo Orlando, Shawn Barron, and Nate McKewon

This provision was one that an ace team of grad students and I noticed when we put together the “Deep Plan, Thin Skin” article that appeared in the Journal of the Society of Architectural Historians a couple of years ago–you can see it most clearly, perhaps, in the ‘fictitious’ glass skin of Lever House. Here, dark green spandrels cover a three-foot upstand and a three-foot downstand spandrel wall of brick, which met a similar code requirement in New York’s prescriptive code at the time.

Chicago’s new code, passed in late 1949 and taking effect on Jan. 1, 1950, was authored by a committee led by John Merrill, of Skidmore, Owings, and Merrill fame, and while most of his efforts went toward liberalizing the code for homebuilding (including the contentious provision for drywall that set off the city’s Plasterers’ union…), the new code did include a much more relaxed approach to exterior walls, referring designers to charts with requirements that now allowed exterior, non-bearing walls to be of just one-hour fire resistance if they faced a ‘street or public way’:

Chicago Building Code, 1951 Revision

Crucially, elsewhere in the provisions, one-hour construction could be relaxed further through the provision of windows of unlimited size–again, if the wall faced a public way or street. Quietly, Merrill’s committee had not only eliminated the requirement for the spandrel wall, it had made the floor-to-ceiling glass curtain wall entirely legal as well.

Reporting on the floor-to-ceiling glass of Mies’ largely unheralded 2933 Sheridan Road block, the Tribune noted that it was the “second” tall building to take advantage of this provision, the first being, of course, Mies’ 860-880 Lake Shore Drive. I’ve made that point before, but with some new archival information I think I can suggest that Mies and his office knew about the code provisions (as would most architects in the city at the time).

Building Permit Record Card, 860-880 Lake Shore Drive, Chicago. UIC Libraries/Microfilm.

The code went into effect on Jan. 1, 1950. Above is the building permit card for 860-880 Lake Shore Drive, first filed on Jan. 20, 1950. In other words, nineteen days after the code took effect. That first filing was for a basement permit only–probably about right for three weeks of engineering and drafting. The permit for the actual superstructure came in August–again, matching an eight-month design and documentation period. In other words, once the code was passed and took effect, Mies’ office seems to have rushed out as succinct and compact a set of drawings as they could to get a permit and get work on the site started, and then settling in to design the remainder of the building.

Promontory Apartments (MvdR, 1949) and 860-880 Lake Shore Drive (MvdR, 1952)

The difference this made architecturally was profound, of course. 860-880 was only built three years after Promontory, and it was the change from spandrel to glass wall that made the biggest difference in terms of appearance. Historians often talk about the switch from concrete to steel in the structure, but in reality 860-880 has so much concrete poured around the frame for fireproofing that this made (I think) far less of a difference than the elimination of that upstand brick wall.

Construction Views, Promontory Apts. (L) and 860-880 Lake Shore Drive (R). Architectural Forum.

But to developers–Herbert Greenwald in the case of the Mies buildings, but others throughout Chicago–would have been just as interested in the different construction methods the new code allowed. “Dry” aluminum installation, of factory-assembled units replaced the time- and labor-intensive “wet” brickwork, saving time, weight, man-hours (union man-hours, not to put too fine a point on it) and cleanup.

Jessica and Federico’s class makes the point that hidden documents like specifications or building codes offer all sorts of alternative histories that connect architecture and building to rich networks of industrial, economic, and labor history, among others. There’s lots more to dig into in both the code story and the building permit archives (note, for example, that the permit was applied for by PACE Architects, not Mies…), but this tidbit seems worth getting out there as a small, index-card sized document that reveals far more than its modest size might suggest…

860-880 Lake Shore Drive. Construction Image. Chicago History Museum. Image forms part of the Hedrich Blessing Collection, 1991.0505. All Rights Reserved. Scan from 8×10 BW negative