Fabrication and erection of the structural steel, metal decking and steel tube for glass penthouse bulkhead. Fabrication and installation of monumental stair with heavy plate stringers and railings. The staircase in this Manhattan duplex consists of milled-metal and glass treads and water-jet-cut, double-sided "sawtooth" plate stringers (1¾ inch). It also features a glass intermediate landing and top platform. The stair has cold-applied, metal-oxide, acid-wash finishes.