OK, continuing on from Monday’s post, here’s a plan of the Monadnock’s northern two bays–the ones designed by Burnham and Root and built in quick succession between 1891 and 1893. What everyone notices, of course, is the thickness of the walls–this plan is from about the eighth floor, so the size of the brick piers actually gets much greater beneath this. Note, too, the cross-walls. There are two of them in the northern wing (to the right), but the southern wing relied more on internal, wrought-iron bracing girders and an elaborate network of diagonal rods buried within the floor plate.
Iron also played a big role in the bits of cladding between the piers. Most commentary on the Monadnock has focused on Root’s ability to detail the brick exterior to appear as a continuous, undulating surface, but even from the architectural plan you can see that the Monadnock was really two very different cladding systems in one. The brick piers served both as enclosure and as structure, while the oriel windows were much lighter, shedding any structural load (carried, instead, by cantilevering wrought iron beams) and serving exclusively as light- and air-gathering devices. (They also, of course, stole square footage from the air over the sidewalk).
The 1890 Pontiac Building, shown at left, was a contemporary of the Monadnock and one of the first (after the 1888 Tacoma, also by H&R) to use the oriel, or bay window, as an element in skyscraper skins. Usually seen in residential applications, these bays provided greater glass surface area and better opportunities for views and ventilation. But they were difficult to construct in masonry and cast iron structures, as the cantilevered floors within them required beams and girders that could take quite a bit of bending. As steel began to find regular use in skyscraper construction, these cantilevered bays were slightly easier to construct. The bays don’t show up on B&R’s 1885 scheme, but they practically dominate the structure as built; technology and materials had clearly changed between the project’s iterations.
Thus, while the Monadnock stands assuredly at the end of the city’s tradition of masonry skyscrapers, Root’s bay windows were far more progressive than the structure is generally give credit for. The Monadnock’s bay windows represented an early use of a device that had been well-tested, but that would also find far greater application on the other ‘veneered’ buildings of the early to mid-1890s. Rather than seeing the building as strictly a masonry structure, we ought to see the Monadnock as a steel building struggling to break out of a masonry cage, and that makes it, I think, even more interesting than the traditional histories have suggested.