An articulated dome of glass and steel now rises from historic Tammany Hall, honoring the building’s namesake on the northeast corner of Union Square in Manhattan. The iconic rooftop addition is the visible top of a new 6-story building rising from within the restored century-old street walls of the New York City landmark. The undulating, turtle-shell-like dome honors the source of Tammany Hall’s name, the legendary Native American Lenape Chief Tammanend. Known for supporting peaceful coexistence with 17th century European settlers, Tammanend inspired pre- and post-revolutionary political clubs to listen to all voices while they debated what a new republic could be.
Dozens of populist Tammany societies dotted the young U.S., but only New York’s Tammany Hall survived into the 20th century. By then, the name Tammany had become synonymous with corruption and greed because of various scandals, including those during the infamous “Boss” Tweed era; Tweed is notorious for stealing money from New York City taxpayers. BKSK Architects LLP’s team believed this project presented an opportunity to provide an overdue correction to Tammany’s legacy.
To refocus public awareness on Tam- many Hall’s namesake, BKSK Architects went back to the building’s roots. Our design team took inspiration from the image of a great turtle rising from the sea—Chief Tammanend’s clan symbol and a scene from the Lenape creation story—to give the Neo-Georgian building the grand dome many Georgian and Neo-Georgian buildings originally had or acquired over time. Along the way, we consulted with the Lenape Center to ensure an appropriate use of cultural symbolism.
A Brief History
The Tammany Hall building on Union Square was not the organization’s first building; however, it was the last. It was designed in 1928 by the Philadelphia architectural firm of Thompson, Holmes and Converse. At the time, the design of the new building was an opportunity to move away from scandal and to rebrand the organization with quasi-governmental cred- ibility by cloaking itself in an architectural language familiar to the founding fathers. The Neo-Georgian design of the building was inspired directly by the original Federal Hall on Wall Street, where George Washington was inaugurated.
The Tammany Hall organization occupied the building from 1929-43, when
it sold the building to the local chapter of the International Ladies’ Garment Workers’ Union. ILGWU started renting the Tammany auditorium to off-Broadway theater companies in the 1980s. One of these, Liberty Theaters, bought the building outright in 1998. Liberty Theaters’ parent company, Reading International RDI, decided to rebrand the building as a commercial retail and office property in 2012 and invited BKSK Architects to a limited design competition, organized by Edifice Realty Services. The overall goals of the project were clear: Reimagine the landmark for commercial use and increase the square footage as much as possible through a vertical expansion (taboo territory for New York City individual landmarks). BKSK Architects’ design won the competition and, in 2015, was approved unanimously by the city’s Landmarks Preservation Commission.
Juxtaposing a classically proportioned yet contemporary glass and steel form above Tammany Hall’s Neo-Georgian masonry base allows the dome to complement the landmark building below, yet provide a showcase for the technology of today. To create a parametric mesh evoking an amphibious shell breaking through the surface of water, our team used various cross-discipline computer modeling and image-rendering software used in automotive, industrial, architectural and video- game design.
Our design team then brought the mathematical representation of the curving 3-dimensional form to life by deploying a self-supporting free-form grid structural system, a system well suited to undulate effortlessly and enclose a great volume of space. Collaborating with engineers at Thornton Tomasetti and Buro Happold, our design team produced an early construction document package that was bid on by 10 European fabricators familiar with free-form grid shells. Ultimately, construction manager CNY awarded a design-assist contract to Josef Gartner, a division of Permasteelisa. Working with BKSK, the engineering team optimized the dome’s geometry to achieve the most efficient use of repeated glass sizes and steel shapes.
The Right Glass
To maximize flexibility of tenable uses under a glass dome, the specification of the right glass became crucial to address occupants’ needs for a low-glare and thermally comfortable environment. Our design team also was challenged with mitigating sunlight reflecting off the convex form onto neighboring buildings while maintaining the imagery of a rising shell shedding water. With those issues in mind, the design team visited glass-roofed buildings near and far.
Of the many local and foreign glass roofs visited, the most informative were Norman Foster’s groundbreaking covered courtyard of the British Museum, completed in 2000, and his 2007 encore covering the courtyard of the Smithsonian Portrait Gallery in Washington, D.C., as well as Helmut Jahn’s freestanding glass egg-shaped Mansueto Library, completed in 2011, emerging from the grounds of the University of Chicago.
Coincidentally, the Mansueto Library’s form and use closely resembled our intentions to create a glass-domed workspace. We noted how the fritted glass of Mansueto Library’s dome performs exceptionally well and was virtually invisible, creating a very low-glare environment with the illusion of clear glass. Our team was inspired to use a similar strategy but quickly learned through sample and mock-up iterations, the effect achieved at Mansueto Library is because of the height of the fritted glass above the occupants; the higher the better.
We learned when frit is closer to one’s eyes, direct sunlight can be perceived between fritted patches, reaching occupants’ eyes, rendering even very closely placed frit useless. We moved on to study combinations of frit, film and tinted glass and eventually chose two insulated-glass-unit assemblies using a combination of clear and tinted glass.
The slightly clearer of the two assemblies encloses the lower areas of the dome where Tammany’s small hipped roof once stood. Terra-cotta sunshades protect portions of this lower tier in the same inclined plane as slate tiles once sat. Strategic placement of projecting painted stainless-steel fins on the exterior of the upper dome offer articulation to the shell and also provide rain and snow control. The most rewarding aspect of the finished project was maintaining a legible image of a rising turtle throughout design and construction using cutting-edge technology and practical everyday elements.
The glass-domed vertical enlargement encloses an additional 30,000 square feet of rentable space over three floors on the top of the historic building with dynamic views of Union Square and beyond. The dome is comprised of more than 2,000 2- by 6-inch steel tube purlins with customized node intersections and varying wall thickness depending on location.
The glass product is a structurally glazed insulated glass unit comprised of a clear float glass panel with a high-performance sputter coat solar coating on surface two, an air space and two layers of laminated glass: a tinted gray panel and a clear glass panel facing the interior.
The solar coating on surface two is an extremely high selectivity solar control with advanced thermal insulation properties for commercial glazing. It is applied by cathodic sputtering under vacuum conditions. The coating creates a low solar factor to reduce air-conditioning load and has a U-value of 1.0W/m2K, encouraging energy savings and improved thermal insulation. Neither too green nor too blue in appearance, the insulated glass units at Tammany Hall’s dome retain a neutral appearance.
A central challenge during the construction phase involved decoupling the historic 100-year-old street walls from the internal structure of the building, bracing them externally, restoring them and then securing them back to a newly poured concrete structure behind. Unexpectedly, it proved more efficient for CNY to remove the lot-line walls against the adjacent neighbors, as well, during demolition of the internal structure, leaving only the historic street walls as original fabric from 1928. The resulting building is truly a new Class A commercial mixed-use building referencing the past and ready for tomorrow. The building received a core and shell temporary certificate of occupancy in 2020 and is being actively marketed by ownership.