GMS was selected as design consultant for the assessment and repair of the Guastavino timbrel dome on top of the Dime Savings Bank building at 9 Dekalb Avenue in Brooklyn, New York. The bank building was opened in 1908, and the dome was added in 1932. The Dime site is under redevelopment as part of the Brooklyn Tower project, a newly built 1035 foot tall tower, completed in 2023, by SHoP Architects and WSP. As part of the redevelopment, the roof over the bank building is set to become an accessible terrace hosting a fitness center, swimming pools and other amenity spaces for residents.
Photo by GMS
Our scope of work included structural analysis and proposing repairs for the structural dome, assessment and repair recommendations for the dome water management system and providing waterproofing for the dome, walls and slabs, assessing the stability of the walls, repairing the high roof slab at the cornice level, and stabilization of the ornamental terracotta cornices. All these elements showed cracks and signs of movement and water infiltration.
The dome showed signs of movement in the terracotta cladding, and water infiltration in the inner Guastavino dome. GMS investigated the structural stability of the dome and the tension ring steel angle at its base. Sixteen probes were performed along the perimeter showing only moderate section loss in the tension ring. These areas are to remain open to allow for periodic inspections. Several methods of structural analysis confirmed that the capacity of the tension ring and the terracotta tiles themselves were well above the stresses calculated by Guastavino Jr.
The issues affecting the structure could be traced back to the damage caused by water infiltration and the associated corrosion. Thus, improving the roofing and waterproofing of the dome, walls and slabs was essential. The existing gutter at the base of the dome was completely unfunctional. GMS proposed installing a new membrane underneath the terracotta cladding to intercept the water above the existing gutter. This strategy allows minimizing the impact on the dome as only the lower course of terracotta cladding needs to be removed and reinstalled. New roofing at the high-slab level was also installed, and damaged or missing terracotta pieces have been repaired or replaced.
The high-roof slab was assessed through visual inspection and sounding. GMS concluded some areas required patching or full replacement. The existing steel beams showed significant corrosion, requiring reinforcement plates at several locations.
Photo by GMS and section of dome identifying different areas.
The ornamental cornice is composed of terracotta supported on a brick wall. Cracked terracotta was observed at the base. Moreover, a 3D scan had shown that the cornice had displaced and rotated outwards. The original steel outriggers were corroded, calling for urgent stabilization. GMS designed a stabilization solution using Cintec anchors through the terracotta pieces connecting to new steel posts, bringing the loads to the existing steel beams below the high-roof slab. This approach allowed for salvaging most of the original terracotta.
The ultimate goal of the work of GMS has been to bring the dome and walls to a safe condition, avoiding full demolition and replacement. This approach means that re-inspections are required every few years to monitor the conditions and ensure the preservation of this historical building. Our recommendations were approved by the Landmarks Preservation Commission and were peer reviewed by John Ochsendorf, a professor in MIT and leading expert in the study of Guastavino structures. The Dome repair was presented at the SEAoNY Annual Conference by Vicente Galvan and Ramon Gilsanz in February and at the Annual Symposium of the International Association for Shell and Spatial Structures IASS-IWSS in Turin, Italy, by Javier Canada on September 15, 2026.
Section of new anchorage repair by GMS