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Height: Occupied
47.9 m / 157 ft
Height: To Tip
54.9 m / 180 ft
Height: Architectural
53.7 m / 176 ft
HL23 Outline
Floors Above Ground
Floors Below Ground
# of Elevators
Tower GFA
3,600 m² / 38,750 ft²
# of Apartments


Official Name HL23
Structure Type Building
Status Completed
Country United States
City New York City
Street Address & Map 515 West 23rd Street
Postal Code 10011
Building Function residential
Structural Material steel
Proposed 2005
Construction Start 2008
Completion 2011
Official Website HL23

Companies Involved

Owner 23 Highline LLC
Developer Alf Naman Developers
Design Neil M. Denari Architects
Structural Engineer
Design DeSimone Consulting Engineers
MEP Engineer
Design ads ENGINEERS
Main Contractor T.G. Nickel and Associates
Other Consultant
Façade Front Inc.

About HL23

Situated on 23rd Street in New York’s Chelsea Arts District, directly adjacent to the High Line (a defunct elevated rail line that has been converted into a 20 block long linear park), HL23 was constructed on a very compact 12x30 m (40x100 ft) site. The volume of the condominium building increases as it rises up. This expanding profile was a direct response to the client demand for more sellable square footage, but it was driven by the particular conditions of the site, not least of which was the High Line itself.

With a captive audience in mind, the building is designed as a complex prism whose proportions, angles, and profiles continue to shift as one walks past on the elevated park. In this sense, although HL23 is a private program, the building participates in the public experience of the park. HL23 thus oscillates between urban infill and object building, mediating the context of near and far views, which reaffirms its optically-complex characteristics. Materially and structurally, the building strives to reflect its prismatic geometry though exposed steel pipe columns and diagonals, and an undulating east façade clad in stamped stainless steel panels.

Except for the cast concrete substructure and some interior finishes and surfaces, all components of HL23 were fabricated off site. With more work done off site, tolerances in most areas were reduced to a minimum, challenging each fabricator to work as close as possible to physical limits. Although prefabrication is a long standing ambition of the industry, here the efforts to raise the level of precision of the building’s components allowed otherwise complex conditions to be resolved more simply. In particular, the north and south curtain walls (produced in Dongguan Province, China) were shipped in mega-panel assemblies allowing for rapid erection and a uniform appearance across the folded surfaces.

CTBUH Initiatives

HL23 Chosen as Featured Building
Mar 2012 – Featured Tall Building

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