Architectural renderings have been released for an ambitious expansion and residential transformation of 809 Madison Avenue, a 12-story building located on Manhattan's prestigious Upper East Side. The comprehensive redevelopment project, designed by the renowned Robert A. M. Stern Architects and developed by Harry Macklowe of Macklowe Properties in partnership with SK Development, will add three additional floors above the existing roofline and completely renovate the interior spaces into luxury single-floor condominium units averaging 4,000 square feet each.

The expansion plans call for significant structural modifications to the 159-foot-tall building, including horizontal expansion on the eastern elevation and the installation of new, larger windows throughout the facade. The most striking addition will be a sprawling penthouse unit situated on the roof level, featuring an expansive 1,500-square-foot private terrace. SLCE Architects serves as the architect of record for the property, which occupies a prime corner location at Madison Avenue and East 68th Street.

The newly released renderings provide detailed comparisons between the current 12-story structure and the proposed 15-story configuration upon completion. Street-level perspectives looking north and west showcase the planned renovations to the brick facade on the southern elevation, designed to match the existing street-facing cladding. The eastern horizontal expansion will rise from the building's existing two-story base, while the three-story roof addition features a distinctive tiered configuration complemented by elegant stone cornices and railings.

Detailed elevation diagrams reveal the transformation of the building's northern face, which will require the removal of two water towers and a mechanical bulkhead to accommodate the three new floors. The eastern expansion incorporates a vertical stack of balconies lined with sleek dark metal railings, while the main western profile displays the stepped arrangement of the new stories alongside an enlarged window grid running down the center of the building. Notably, the ground-floor retail frontage will remain unchanged.

The developers acquired the building, which had been sitting vacant for approximately three years, in a $49 million transaction from Churchill Real Estate. The deal was brokered by Avison Young's team of Alexandra Marolda, Brent Glodowski, and Eric Karmitz representing the seller. The previous owner had purchased 809 Madison Avenue in 2019 for $55 million and separately sold the retail portion of the property to the Jackson Group for $9 million in 2024.

Financing for the project involves multiple prominent real estate investment firms. A construction loan is being provided through a partnership between Infinite Global Partners, led by former Silverstein Properties CEO Marty Burger, and Related Funds. Additional preferred equity funding comes from Sculptor Capital Management and Circle Property Partners, with Michael Campbell of the Carlton Group arranging the comprehensive financing package.

The proposed exterior modifications and expansion have received approval from the Landmarks Preservation Commission, a crucial regulatory step given the property's location within the Upper East Side Historic District. Harry Macklowe plans to utilize available air rights to facilitate the structural expansion. Individual condominium units are expected to be priced at more than $20 million each, reflecting the luxury market positioning of the development.

The building's location offers convenient access to public transportation, with the closest subway station being the 6 train at 68th Street-Hunter College, situated two avenues east of the property. However, specific details regarding the construction timeline and total unit count for the 809 Madison Avenue project have not yet been announced by the development team.