With a design complementing its landmarked neighbor, the transformation of One Madison Avenue brings flexible, Class-A office space to Manhattan’s Flatiron District.

---

Revamping a Historic Icon

Bounded by Park and Madison Avenues between East 23rd and 24th Streets, One Madison transforms the block it shares with the historic Five Madison clock tower. A site shaped by centuries of civic life, its redevelopment brought together the Madison Square Park Conservancy, the New York Landmarks Conservancy, the local community board, and public officials to ensure the project remained deeply rooted in its context.

The existing building has a strong history of adaptive reuse. Starting in 1983, the building designed by Napoleon Le Brun & Sons expanded with the Metropolitan Life Insurance Company and has continued to adapt to the evolving needs of corporate offices.

Bringing the Context Closer

Madison Square Park rests across the street from One Madison and has been a center of civic life since it opened in 1836. It anchors some of the city’s most vibrant neighborhoods—Chelsea, Gramercy, NoMad, and the Flatiron District—with Michelin-star dining, unique shopping, and cultural resources on every corner. Our design draws this energy directly into the building. Over an acre of landscaped terraces and rooftop gardens pull the park’s greenery inward and extend it vertically through the tower.

Doubling the Useable Space

The 1960s office building preceding One Madison did not have the capacity to meet the demand for its coveted Midtown location but gave the project a substantial foundation from which to build. Current zoning regulations and the landmarked clock tower would have greatly restricted the possibility of One Madison’s design if it had been demolished and rebuilt. Instead, the KPF team leveraged the existing building’s full-block footprint, underutilized floor area allowed by outdated zoning regulations, and historic relationship to the clock tower to maximize the available square footage of the site.

The complex adaptive reuse strategy densified the site through selective demolition of the setback floors and their replacement with a new, highly efficient 550,000-square-foot tower. Creative design and construction solutions allowed One Madison to retain 67% of its existing structure and achieve an estimated embodied carbon reduction of 20,000 tons of CO₂ compared to an entirely new building. The project’s simultaneous selective demolition and reconstruction process, all while keeping the clock tower’s hotel fully operational, posed significant engineering challenges that required extraordinary coordination.

Crafting Continuity

The material choice allows for a delicate transition between the retained podium and the modern jewel box above. At the podium, the original Alabama limestone façade is preserved and restored—requiring significant construction coordination, design ingenuity, and devotion to the site’s history and context.

Balanced on a series of trusses, the new 14-story tower is clad in a glass curtainwall façade with projecting aluminum fins and an expressed side-core wrapped in Jet Mist granite. Blackened steel envelopes the transfer trusses at the garden floors and a dark wood introduces warmth in the shared spaces throughout. The tower rises and sets itself apart as a distinctly modern addition to the complex—deliberately set back from the clock tower to integrate the project into the neighborhood while highlighting its landmarked neighbor.

Creating the Workplace of the Future

One Madison provides a successful example of how development can meet the demands of an evolving market, add value to existing buildings, preserve embodied energy, and improve operational performance. Inside, the renovation introduced large, open floor plates designed for a contemporary workplace. A dedicated outdoor air system provides 100% outdoor air, increases available ceiling heights through reduced duct sizes, improves indoor air quality through better filtration and individual controls, and contributes to lower operational and lifecycle costs.

One Madison Avenue has achieved extraordinary market acceptance, with 100% of its office space leased within its first year to a diverse mix of global technology, financial, and professional service firms. The innovative side-core layout enabled flexible, efficient floorplates and improved energy performance, with glazing maximized to reflect modern tenant needs.

A Model for Sustainable Reuse

The project is designed to comply today with the 2030 building emission targets determined by NYC’s Local Law 97. By retaining 67% of the building’s original structure, a significant amount of embodied energy was reused and saved—equivalent to the total operational carbon produced over 20 years of the new building’s operation.

---