HL23

New York City
Height
1
To Tip:

Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the highest point of the building, irrespective of material or function of the highest element (i.e., including antennae, flagpoles, signage and other functional-technical equipment).

54.9 m / 180 ft
2
Architectural:

Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the architectural top of the building, including spires, but not including antennae, signage, flag poles or other functional-technical equipment. This measurement is the most widely utilized and is employed to define the Council on Tall Buildings and Urban Habitat (CTBUH) rankings of the "World's Tallest Buildings."

53.7 m / 176 ft
3
Occupied:

Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the highest occupied floor within the building.

47.9 m / 157 ft
1 2 3 HL23 Outline
Floors
Above Ground

The number of floors above ground should include the ground floor level and be the number of main floors above ground, including any significant mezzanine floors and major mechanical plant floors. Mechanical mezzanines should not be included if they have a significantly smaller floor area than the major floors below. Similarly, mechanical penthouses or plant rooms protruding above the general roof area should not be counted. Note: CTBUH floor counts may differ from published accounts, as it is common in some regions of the world for certain floor levels not to be included (e.g., the level 4, 14, 24, etc. in Hong Kong).

14
Below Ground

The number of floors below ground should include all major floors located below the ground floor level.

1
Height 53.7 m / 176 ft
Floors 14
Official Name
The current legal building name.

HL23

Type
CTBUH collects data on two major types of tall structures: 'Buildings' and 'Telecommunications / Observation Towers.' A 'Building' is a structure where at least 50% of the height is occupied by usable floor area. A 'Telecommunications / Observation Tower' is a structure where less than 50% of the structure's height is occupied by usable floor area. Only 'Buildings' are eligible for the CTBUH 'Tallest Buildings' lists.

Building

Status
Completed
Architecturally Topped Out
Structurally Topped Out
Under Construction
Proposed
On Hold
Never Completed
Vision
Competition Entry
Canceled
Proposed Renovation
Under Renovation
Renovated
Under Demolition
Demolished

Completed

Completion

2011

Country
The CTBUH follows the United Nations's definition of Country, and thus uses the lists and codes established by that organization.

United States

City
The CTBUH follows the United Nations's definition of City, and thus uses the lists and codes established by that organization.

New York City

Address

515 West 23rd Street

Function
A single-function tall building is defined as one where 85% or more of its usable floor area is dedicated to a single usage. Thus a building with 90% office floor area would be said to be an "office" building, irrespective of other minor functions it may also contain.

A mixed-use tall building contains two or more functions (or uses), where each of the functions occupy a significant proportion of the tower's total space. Support areas such as car parks and mechanical plant space do not constitute mixed-use functions. Functions are denoted on CTBUH "Tallest Building" lists in descending order, e.g., "hotel/office" indicates hotel function above office function.

residential

Structural Material
Steel
Both the main vertical/lateral structural elements and the floor spanning systems are constructed from steel. Note that a building of steel construction with a floor system of concrete planks or concrete slab on top of steel beams is still considered a “steel” structure as the concrete elements are not acting as the primary structure.

Reinforced Concrete
Both the main vertical/lateral structural elements and the floor spanning systems are constructed from concrete which has been cast in place and utilizes steel reinforcement bars.

Precast Concrete
Both the main vertical/lateral structural elements and the floor spanning system are constructed from steel reinforced concrete which has been precast as individual components and assembled together on-site.

Mixed-Structure
Utilizes distinct systems (e.g. steel, concrete, timber), one on top of the other. For example, a steel/concrete indicates a steel structural system located on top of a concrete structural system, with the opposite true of concrete/steel.

Composite
A combination of materials (e.g. steel, concrete, timber) are used together in the main structural elements. Examples include buildings which utilize: steel columns with a floor system of reinforced concrete beams; a steel frame system with a concrete core; concrete-encased steel columns; concrete-filled steel tubes; etc. Where known, the CTBUH database breaks out the materials used in a composite building’s core, columns, and floor spanning separately.

steel

Official Website

HL23

Height
Architectural
Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the architectural top of the building, including spires, but not including antennae, signage, flag poles or other functional-technical equipment. This measurement is the most widely utilized and is employed to define the Council on Tall Buildings and Urban Habitat (CTBUH) rankings of the "World's Tallest Buildings."

53.7 m / 176 ft

To Tip
Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the highest point of the building, irrespective of material or function of the highest element (i.e., including antennae, flagpoles, signage and other functional-technical equipment).
54.9 m / 180 ft
Occupied
Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the highest occupied floor within the building.
47.9 m / 157 ft
Floors Above Ground
The number of floors above ground should include the ground floor level and be the number of main floors above ground, including any significant mezzanine floors and major mechanical plant floors. Mechanical mezzanines should not be included if they have a significantly smaller floor area than the major floors below. Similarly, mechanical penthouses or plant rooms protruding above the general roof area should not be counted. Note: CTBUH floor counts may differ from published accounts, as it is common in some regions of the world for certain floor levels not to be included (e.g., the level 4, 14, 24, etc. in Hong Kong).

14

Floors Below Ground
The number of floors below ground should include all major floors located below the ground floor level.

1

# of Apartments
Number of Apartments refers to the total number of residential units (including both rental units and condominiums) contained within a particular building.

11

# of Elevators
Number of Elevators refers to the total number of elevator cars (not shafts) contained within a particular building (including public, private and freight elevators).

1

Tower GFA
Tower GFA refers to the total gross floor area within the tower footprint, not including adjoining podiums, connected buildings or other towers within the development.

3,600 m² / 38,750 ft²

Construction Schedule
2005

Proposed

2008

Construction Start

2011

Completed

Structural Engineer
Design

The Design Engineer is usually involved in the front end design, typically taking the leadership role in the Schematic Design and Design Development, and then a monitoring role through the CD and CA phases.
DeSimone Consulting Engineers
Other Consultant

Other Consultant refers to other organizations which provided significant consultation services for a building project (e.g. wind consultants, environmental consultants, fire and life safety consultants, etc).
Façade

These are firms that consult on the design of a building's façade. May often be referred to as "Cladding," "Envelope," "Exterior Wall," or "Curtain Wall" Consultant, however, for consistency CTBUH uses the term "Façade Consultant" exclusively.
Front Inc.
Owner
23 Highline LLC
Developer
Alf Naman Developers
Architect
Design

Usually involved in the front end design, with a "typical" condition being that of a leadership role through either Schematic Design or Design Development, and then a monitoring role through the CD and CA phases.
Neil M. Denari Architects
Structural Engineer
Design

The Design Engineer is usually involved in the front end design, typically taking the leadership role in the Schematic Design and Design Development, and then a monitoring role through the CD and CA phases.
DeSimone Consulting Engineers
MEP Engineer
Design

The Design Engineer is usually involved in the front end design, typically taking the leadership role in the Schematic Design and Design Development, and then a monitoring role through the CD and CA phases.
ads ENGINEERS
Contractor
Main Contractor

The main contractor is the supervisory contractor of all construction work on a project, management of sub-contractors and vendors, etc. May be referred to as "Construction Manager," however, for consistency CTBUH uses the term "Main Contractor" exclusively.
T.G. Nickel and Associates
Other Consultant

Other Consultant refers to other organizations which provided significant consultation services for a building project (e.g. wind consultants, environmental consultants, fire and life safety consultants, etc).
Façade

These are firms that consult on the design of a building's façade. May often be referred to as "Cladding," "Envelope," "Exterior Wall," or "Curtain Wall" Consultant, however, for consistency CTBUH uses the term "Façade Consultant" exclusively.
Front Inc.

CTBUH Awards & Distinctions

Best Tall Building Americas 2011 Award of Excellence

2011 CTBUH Awards

CTBUH Initiatives

HL23 Chosen as Featured Building

1 March 2012 - Featured Building

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 Awards & Distinctions

Best Tall Building Americas 2011 Award of Excellence

2011 CTBUH Awards

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