171 Duane is a cast-iron facade loft building built in 1803 located in the Tribeca West Historic District The building was converted to artists-in-residence lofts in 1970. In 1999, in the context of a routine roofing investigation, our team observed that the building was leaning and the parapet was separating from the roof. Subsequent investigations determined that the east wall along Staple Street was leaning out of plumb position by more than 24″, was undergoing continued movement and had the potential for collapse. With our  structural engineering team we confirmed that the wall had to be removed and the building structurally stabilized. Restoration called for removal of the entire east wall and the installation of a permanent structural steel frame within the building to support the building. The building was fully occupied during this construction. Ultimately a new steel structure was installed supporting all of the floors, roof, and walls of the building,