In 2018 SL Green, the property manager of One Madison Ave announced plans to redevelop the property. This required demolishing the 13 stories down to the top of the 9th floor to accommodate the rehab and addition to the building. The new addition will have 27 floors and will have a glass tower façade with terraces on the 10th, 11th, and the 27th floors and add 530,000 sq. feet to the building. This will accommodate more retail and office space in the Flatiron District.

Kohn Peterson & Fox has enjoyed working with SL Green over the years, recently on One Vanderbilt Avenue and now on One Madison Avenue, which is very different from its taller cousin in Midtown, but we think will have an equally dramatic and positive impact on the city,” said Doug Hocking, AIA, KPF design principal. “We wanted to preserve the character of the original building but also open it up so we could extend the nature of the adjacent park through the tower. When completed, we’re confident that One Madison will be a dynamic, inspiring workplace for the 21st century.”

The One Madison Avenue project cost was around 1.2 billion financed by National Pension Service of Korea and Hines. Banker Steel Company completed the structural steel for the One Madison project in New York, NY in November of 2023. The steel used in One Madison was fabricated in the Virginia, New Jersey, and Florida plants of Banker Steel Company. The new building stands at 27 stories. The top floors of the One Madison is where you will find the galvanized steel members. The top floors is where the steel members are exposed to the environment. Hot-dip galvanizing was chosen for the corrosion performance and the longevity of the coating. Over the course of time this will minimize preventative maintenance and allow the steel framing to last for decades to come to house mechanical equipment to provide energy to the building.