Tammany Rising: BKSK’s Turtle-Shell Dome and the Re-Making of 44 Union Square

A building is never just brick and steel - Its memory, identity and civic choreography that can sometimes be glorious, yet sometimes thorny. Tammany Hall at 44 Union square was once a crown jewel of the political scene, yet as it transitioned to modern day, it was seen as a worn building, and its historical past of the dominant Tammany political machine hub (known for its power brokerage, corruption and exploiting of immigrants) seemed to vanish. BKSK’s renovation of the rooftop dome turned history inside and out: It preserved the old famous facade and renovated the interior into a modern office and retail space, and added a freeform glazed dome inspired by the Lenape turtle myth,  a tribute to its political past. The project is equal parts preservation, engineering feat and cultural act — and the technical record and published interviews make that clear.

The old site — history and civic context

Tammany Hall building ( the site itself had a much longer past), was designed and renovated again by Thompson Holmes & Converse and Charles B. Meyers in 1928–29 and sat at the northeast corner of Union Square. In 2013, the city designated the building as a historical landmark, but the interior was functionally obsolete. The owner of the site sought to convert it into a commercial and retail space while preserving the famous facade, setting the stage for an adaptive reuse and historical preservation project. 

BKSK, the Lenape Center, and the design philosophy

The motto for the renovation, if you could call it a motto, was “restore the street presence, adapt the interior, and respect historical nature while making it a contemporary marker.” Rather than replace the building itself with a new imposing marker, BKSK sought an additive subtle yet elegant dome: making it both a modern rooftop yet echoing the classical domes that  Georgian buildings often acquired over time. Todd Poisson (BKSK partner) describes the intent plainly: the team “took inspiration from the image of a great turtle rising from the sea — Chief Tammanend’s clan symbol — to give this Neo-Georgian building the grand dome many Georgian and Neo-Georgian buildings originally had.” 

That cultural framing was not decorative tokenism. BKSK reached out to the Lenape Center, which advised the team and performed a blessing ceremony at the completed structure; Lenape leaders Joe Baker and Hadrien Coumans have publicly stated that the collaboration was thoughtful and restorative — an effort to recover indigenous presence and meaning in the city’s fabric. As Joe Baker put it, the dome “is a beacon for the future, calling the grandchildren home to Manhattan.” Hadrien Coumans praised the “thorough consultation” and the project as a rare local example of architects engaging Indigenous peoples through the design process.

How they did it — the technical story, step by step

1. Facade bracing and careful demolition
Since only the North and west faces of the building were considered the landmark icon, the team was able to remove most of the interior without tampering with the protected faces. They braced, shored and monitored everything and demolished everything else. They hired Howard Shapiro and his team to design the internal and external steel walers and towers to sandwich the structure to keep it stable during demolition and reconstruction. 

2. New reinforced concrete interior and foundations

BKSK and structural engineer Thornton Tomasteii created a new concrete frame of 11 inch floorslabs, 12 inch shear walls for lateral resistance and concrete pier casts around the existing steel columns where reinforcement was needed. On the eastern side of the project, the rock depth had significant variation, thus requiring the use of micropiles in order to avoid excavation. 

3. The dome: parametric geometry + prefabricated steel and glass

The dome is the project’s technical signature. BKSK modeled a free-form grid shell with parametric tools (Rhino, V-Ray, Maya, 3ds Max) to generate an organic, turtle-shell geometry that could nevertheless be rationalized into repeatable elements. The grid comprises roughly 2,000 steel tube purlins (≈2"×6") with customized node intersections; lower sections were welded, higher sections bolted to allow assembly tolerance. Fabricator Josef Gartner (Permasteelisa division) led a design-assist process to optimize panel sizes and steel shapes to minimize fabrication complexity. The dome contains about 800+ triangular insulated glass units covering ≈12,000 sq ft, and the whole glazed shell spans roughly 150 ft × 75 ft

Todd Poisson explains the glazing choices plainly: after visiting glazed roofs (from Foster’s covered courtyard at the British Museum to Jahn’s Mansueto Library), the team experimented with combinations of frit, film and tinted glass. They ultimately specified two insulated-glass assemblies (clear + tinted Planitherm/Parsol components) with laminated inner layers to reduce glare and solar gain while preserving the shell’s “shedding water” imagery. Terra-cotta sunshades occupy the same inclined plane as the original slate roof to recall the building’s past while helping solar control. 

4. Offsite prefabrication and tight on-site logistics

The dome’s sections were prefabricated offsite — the steel grid, nodes, and glazing units were manufactured and trial-assembled in Europe then shipped for erection. Given Union Square’s congestion and limited laydown, offsite work was essential: pieces were craned and bolted together like a kit-of-parts on a tight Manhattan footprint. Buro Happold provided façade engineering and co-ordination; Thorntons handled structural integration; Dagher Engineering handled MEP integration. 

5. Heritage restoration and visible continuity

While new concrete piers and slab systems provided the building’s technical backbone, the team worked hard to re-attach the preserved façades to the new frame with steel clip angles and epoxy anchors — reclaiming bricks where possible, and replacing parapets, balustrades and stonework using a combination of salvaged and new masonry. Higgins Quasebarth & Partners guided the historic preservation approach.

Todd Poisson (BKSK partner) on intent and craft: “We took inspiration from the image of a great turtle rising from the sea — Chief Tammanend’s clan symbol — … Along the way, we consulted the Lenape Center to ensure appropriate use of cultural symbolism.” He also described the dome’s technical anatomy: “The dome is comprised of over 2,000 2”×6” steel tube purlins … and 850 triangular insulated glass units … we studied combinations of frit, film, and tinted glass and eventually chose two insulated glass unit assemblies.”

Marco Coco (Thornton Tomasetti) on tricky geotechnics and support: the team used micropiles where rock depth varied so “we didn’t have to keep digging and potentially undermine the neighboring buildings,” and relied on reinforced-concrete shear walls and monolithic pours to tie new piers into the old façade footings.

Joe Baker (Lenape Center) on meaning: “Our history is complex… The turtle dome of Tammany Hall is a beacon for the future, calling the grandchildren home to Manhattan.” (Metropolis coverage quoting Baker.)

Hadrien Coumans (Lenape Center) on collaboration: he called BKSK’s consultation “thoughtful” and said the dome is “rare to have an example in the city of thorough consultation that resulted in something that is really a new landmark.” (Urban Omnibus / BKSK repost.)

Key risks and how they were managed

  1. Losing the façades during demolition: mitigated with heavy external and internal bracing and live monitoring for vibration/cracking. 

  2. Foundations near shallow rock and adjacent buildings: mitigated by selective use of micropiles and monitored excavation.

  3. Glare and neighbour reflections from a convex glazed shell: addressed through glass selection (tinted + coated IGUs), placement of stainless fins, and terracotta sunshades respecting the original roofline. 

On-site assembly in dense urban setting: handled by extensive prefabrication and design-assist with Josef Gartner to limit assembly time and improve quality control.

Reception, impact and continuing questions

The completed 44 Union Square reopened the corner as Class-A commercial space with restored storefronts and a dramatic new rooftop. The project won attention for the technical courage (free-form dome) and for the cultural outreach (Lenape consultation and blessing). It received awards for restoration/safety and generated civic discussion about how to reinterpret contested histories in the city’s physical fabric. As BKSK’s Poisson said at the opening, they “hope the dome makes people pause and become curious about the Lenape influence that surrounds us here in Manhattan.” 

At the same time, the project raises longer questions that often accompany high-profile adaptive reuse: Who gets to rebrand and retell civic memory? Does a single iconic move (a shiny dome) adequately address the deeper social legacies of a place whose name is inseparable from machine politics? BKSK made a technical and symbolic attempt to answer “yes” — by involving the Lenape Center, preserving tangible historic fabric, and crafting a dome that is both engineered sculpture and usable space. Critics and admirers will continue to debate whether the gesture fully resolves the building’s complex past — but technically and formally it is a clear demonstration of how advanced parametric design, careful preservation practice, and cross-disciplinary engineering can combine to produce something new out of an old civic artifact. 

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