Because toddlers, older children, and foolish adults fall off unprotected ledges, model building codes (and codes adopted by the various states, based on the model codes) require that guard rails be placed at such dangerous edges. The actual 2020 NYS Building Code language is as follows (Section 1015): “Guards shall be located along open-sided walking surfaces … that are located more than 30 inches (762 mm) measured vertically to the floor or grade below at any point within 36 inches (914 mm) horizontally to the edge of the open side.” In other words, if there is a vertical discontinuity at the edge of a walking surface of more than 30 inches (762 mm), even if that drop of 30 inches (762 mm) occurs up to three feet (914 mm) away from the edge of the walking surface, then a guard is required. Furthermore, the guard must be at least 42 inches (1067 mm) high and it must be configured such that a 4-inch-diameter (102 mm diameter) sphere cannot pass through. This latter requirement is intended to prevent children from sticking their heads through the guard and getting stuck (yes, this really happens!).

Now, I haven’t been able to track down the NYS Building Code in effect when the addition to Cornell’s Uris Library, designed by Gunnar Birkerts, was designed and built in 1980–1982, but the lack of a compliant guard seems consistent with the standards currently in place and, presumably, with the standards in place in the early 1980s (see Figure 1).

Figure 1. The addition to Uris Library at Cornell is altered using PhotoShop to show a more precipitous vertical drop from the walking surface (left); the addition is shown as it actually appears, still with a dangerous vertical drop from the walking surface (right). Photo and PhotoShop manipulation by Jonathan Ochshorn.

This is because, even though there is a vertical drop of much more than 30 inches (762 mm), this drop does not occur within 36 inches (914 mm) of the walking surface: there is a sloping ledge between the walking surface and the precipitous drop which appears to justify the lack of a code-compliant guard (the horizontal pipe rail at the edge of the walking surface does not comply with the requirement that a 4-inch-diameter (102 mm diameter) sphere, let alone a rambunctious toddler, cannot pass through. Yet, as can be seen in Figure 1, the condition is still quite dangerous, since a toddler or child (or spaced-out adult) could easily run through the open guard, slide down the inclined ledge, and fall to the ground below, possibly sustaining serious injuries.

Now, if the walking surface of the addition were at the top of a very tall building, as modeled in Figure 1, left, the architects may well have felt the need to make a safer guard rail, even though the building code would not have required that they do so! The as-built condition shown in Figure 1, right,  is also quite dangerous, and really should have a guard that meets the standards outlined in the building code.

It turns out that the International Code Council (ICC)—which writes the International Building Code (IBC), which, in turn, forms the basis of the New York State Building Code—has fixed this unsafe loophole in the 2024 IBC, not yet adopted in New York State (in fact, the older 2021 IBC has not even been adopted by New York State; as of this writing, New York State’s 2020 Building Code is actually based on the 2018 IBC!). The latest IBC adds “and at the perimeter of occupiable roofs” to the code section (1015.2) which describes where such guards are required. Since the walking surface at the top of the Uris Library addition is an “occupiable roof,” a safe guard rail would be required under that code.

Even though the current unsafe conditions are “grandfathered” under the older code, Cornell should modify the existing pipe rail and turn it into a real guard, as will eventually be required for new construction once the 2024 IBC is adopted.

I had created a free online calculator to determine allowable heights, number of stories, and floor area, based on various criteria in the International Building Code (IBC). This calculator, however, was getting old and out of date, so I finally revised it, based on the 2021 and 2024 IBC (the latest iterations currently available). It’s free and (relatively) easy to use, so try it out, here.

Generic site plan showing various parameters for the calculation of the area increase factor (for frontage).