THE FORMER TAMMANY HALL HEADQUARTERS has a lively history, housing not only the New York Democratic Party organization but also, later, the International Ladies’ Garment Workers’ Union, the Union Square Theatre, and the New York Film Academy. For a mere three-and-a-half-story structure, the 1929 building by Thompson, Holmes & Converse and Charles B. Meyers has carried substantial weight among the city’s institutions. Modeled loosely after Federal Hall, and landmarked in 2013, Tammany Hall underwent a gut rehabilitation to preserves the facade and adds a striking new domed roof, with a grid shell of 2-by-6-inch steel tubes supporting over 800 unique triangular glass units, extending the building’s usable space to six stories.
The parametric steel-and-glass structure atop the neo-Georgian shell’s brick, limestone, and terra-cotta tracery is a stylistic surprise but, to some observers, incongruously harmonious. Todd Poisson, partner at BKSK Architects, recalled the extensive historical research that led to the design after owners Reading International, a theater/real estate firm, invited architects to reimagine Tammany Hall. Recalling the competition brief, Poisson says, “They wanted to move away from the name Tammany, which referenced the Lenape chief Tamanend,” a clan leader of indigenous peoples from the northeastern woodlands. But he and his colleagues took a contrary approach— “Why don’t we re-embrace the name Tammany in a way that they wouldn’t expect and look at Tammany’s history?”—and won.
The architects consulted with the Lenape Center on questions of cultural authenticity and developed a parti that would replace the building’s “pretty tepid slate hip roof” with a dome evoking not only a turtle shell rising from the sea (an image from the Lenape narrative of the North American continent’s creation, and the icon of Tamenend’s clan) but also the domes that were common in Georgian and neo-Georgian design. The Tammany Society’s previous headquarters on 14th Street was domed, Poisson noted, and in England and the U.S., “there were some references we found that got their domes 100 years after they were built…. Using that as inspiration, and other classical domes throughout the history of architecture, we modeled our dome to honor Tamanend with a little organic source material,” commingling Lenape and English heritage. Only this dome would be executed in steel and glass.
A structure driven by such symbolism required exceptional precision in design and construction. Stefan Zimmerman, senior branch manager at the Würzburg, Germany, branch of Josef Gartner GmbH, a member of the Permasteelisa Group, pointed out that the roof is a true free-form design, not a pure dome based on fixed circular radii or ellipses. “This means that every single member is different in shaping and different in geometry, different in angles,” Zimmerman explains. “So the individual surfaces of the canopy have been broken down into triangles.” Such a geometry, he adds, “creates angles between the tubes, it creates angles between the nodes, it creates torsional twists for the tubes, which all need to be accommodated in the node points.” The tubes are relatively simple with a 90-degree end connection, and the complex node points are CNC-machined. Wrapping the dome frame above an arched pediment at the 17th Street entrance created particular geometric challenges. None of the glass is curved; the precise design and machining generates the appearance of curvature with large numbers of small straight steel members, joined at approximately 1,000 node points, supporting triangular double-pane insulated glazing units (IGUs), each combining SGG Cool-Lite Xtreme and Parsol Grey glass panels by Eckelt. “The upper dome glass on the fifth and sixth floors has a darker tint to address glare and thermal comfort, while the lower hipped roof zone glass is slightly clearer, as it is a clerestory glazing for the fourth floor, and is partially shaded by the terra-cotta sunshades,” says Poisson.
Because of fire-protection regulations, Zimmerman says, “the wall thicknesses of the steel are higher than they would have needed to be for structure and for deflection requirements.” The dome is fully self-supporting, and a new concrete liner wall at the perimeter takes the steel structure’s entire load, with no columns touching the steel structure and no internal loading onto the floor plates. The unique shapes of all components called for exceptional logistical control on the job site, along with caution in packing and handling.
Prefabrication of tubes and nodes at Gartner’s German factory included steel lettering to guide assembly. A system of offsite storage and regular shipments to “feed the site with the demand for the next two, three days” overcame storage limitations at the tight downtown Manhattan site.
Rayhaan Nagrath, project manager at Gartner’s New York office, points out that the dome includes areas with two roof types, designated RT1 for the dome and “bull nose” (a protruding segment atop the western facade toward Union Square) and RT2 for the lower perimeter glass. “The bull nose breaks up the two systems,” Nagrath notes, “and the frames for the RT1 and the RT2 are constructed differently.” The RT1 frames include a node system, connecting node to node with horizontal purlins, with a hole in each node as a modular design feature allowing optional mountings, while RT2 frames are composed of purlins without nodes. Purlins include bolts for sprinkler attachment. Support brackets separated from the steel allow the entire structure to move under wind loads, preventing bending and glass breakage. Steel fins placed strategically 11⁄2 inches above the glass articulate the form to help create a dynamic image from the street, and act as a net to disperse snow loads and prevent unexpected avalanches. A hip-roof segment below the dome uses terra-cotta sunshade panels in multiple shades of gray, helping control solar gain and providing visual variety.
“We really wanted to be harmonious with the landmark base building,” Poisson comments. The fins “serve as further articulation of the shell, to make it more harmonious with the scale of both the stonework of the base and the tracery of the window mullions and muntins, especially at the second floor. There’s a balcony with doors with beautiful tracery muntins above it, which we replaced in kind. So we were inspired by the details of the existing building for the scale and detailing of the dome. We wanted to have enough articulation so it did not appear alien.”
After factory pre-assembly of the RT2 frames, installation of both the dome and the terra-cotta panels proceeded from the top down. The total assembly uses approximately 50 frames and 300 purlins to support its 800 glazing units; “pretty much every aspect of this job is unique,” Nagrath says. With its custom components and a high degree of structural interdependence, plus limited space for shoring points during construction because scissor lifts needed room to move, tolerances throughout the frames had to be extraordinarily tight, meticulously checked, and adjusted at each step. The pace of construction, he reported, was “about a frame a day, plus some time for all the intermediate purlins,” plus the glazing, averaging 13 glass units per seven-hour workday.
This painstaking process has yielded a building that has begun garnering honors before even opening, winning an AIA-New York QUAD Design Award in 2017. Zimmerman notes that Tammany may be a difficult precedent to replicate elsewhere. “This is more like a piece of art than a real building envelope,” he says, and he knows of no comparable domes in New York. But the sentiment behind it is one that could inspire architecture the world over; it has restored one of New York’s long-neglected treasures to the public eye.