5085
Global
Height rank

United Nations Secretariat Building

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).

154.3 m / 506 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."

154.3 m / 506 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.

140.8 m / 462 ft
1 2 3 United Nations Secretariat Building 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).

39
Below Ground

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

3
Height 154.3 m / 506 ft
Floors 39
Official Name
The current legal building name.

United Nations Secretariat Building

Other Names
Other names the building has commonly been known as, including former names, common informal names, local names, etc.

UN Headquarters, U.N. Building

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

1953

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

750 1st Avenue

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.

office

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

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."

154.3 m / 506 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).
154.3 m / 506 ft
Occupied
Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to the highest occupied floor within the building.
140.8 m / 462 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).

39

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

3

# 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).

20

Top Elevator Speed
Top Elevator Speed refers to the top speed capable of being achieved by an elevator within a particular building, measured in meters per second.

6.1 m/s

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.

82,272 m² / 885,568 ft²

Rankings
#
5085
Tallest in the World
#
2043
Tallest Office Building in the World
#
472
Tallest Office Building in North America
#
426
Tallest Steel Building in the World
#
267
Tallest Steel Building in North America
Construction Schedule
1947

Construction Start

1953

Completed

2010

Retrofit Start

2013

Retrofit End

Owner
Current
United Nations
Developer
William Zeckendorf
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.

Le Corbusier; Oscar Niemeyer; Wallace K. Harrison

Retrofit Companies Involved

Owner
Current
United Nations
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.

Heintges & Associates; HLW International
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.

HLW International
Project Manager

The CTBUH lists a project manager when a specific firm has been commissioned to oversee this aspect of a tall building’s design/construction. When the project management efforts are handled by the developer, main contract, or architect, this field will be omitted.

Gardiner & Theobald
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.

Skanska
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).

Acoustics
Shen Milsom Wilke, Inc.
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.

Interiors
HLW International
Landscape
di Domenico + Partners, LLP
Lighting
HLW International
Security
Sustainability
HLW International; Viridian Energy & Environmental, LLC

CTBUH Awards & Distinctions

Best Tall Building Americas 2014 Award of Excellence

2014 CTBUH Awards

CTBUH Initiatives

Videos

26 October 2015 | New York City

United Nations Secretariat: Renovation of a Modernist Icon

Michael Adlerstein shares his insights into how the United Nations Secretariat Building, an aging icon of Mid-century Modernism, was renovated to meet the security, efficiency...

Research

26 October 2015

United Nations Secretariat: Renovation of a Modernist Icon

Michael Alderstein, United Nations

Michael Adlerstein shares his insights into how the United Nations Secretariat Building, an aging icon of Mid-century Modernism, was renovated to meet the security, efficiency...

About United Nations Secretariat Building

The Secretariat tower is arguably the most visible representation of postwar optimism and resiliency on the United Nations campus. It also embodies a mid-century Modernist merging of technology and form, as expressed in the remarkably slim north-south facing profiles and the crystalline east-west elevations.

When the multi-billion dollar renovation of the UN campus started, the Secretariat, which has never ceased to operate as a functional government building, was plagued by severely outdated fixtures, deficient life safety features, and a leaky curtain wall. It is estimated that the historic building had operated at least 35 years past its normal lifespan.

Key design strategies for increasing performance included the extensive redevelopment of the base building core and systems, including new elevator systems and mechanical infrastructure, new fire protection systems and code upgrades, disabled-access compliance, and asbestos abatement. Floor plate utilization was enhanced through the introduction of a new planning diagram. It also involved installing a better, more efficient envelope for insulation and blast protection.

The Secretariat was the first tall building to employ a suspended wall system. Its primary elevations were enclosed by free-hanging glazed facades. The new curtain wall was designed to look like it did when it first opened—sleek and taut, with its double-hung aluminum windows, glazed spandrel panels, and aluminum-clad steel mullions appearing as one continuous transparent form. The replaced wall’s appearance had been significantly altered after nearly 60 years of patches, caulkings, insulating and blast coatings, resulting in a patchwork appearance and a greenish hue.

To rectify this, the project team conducted extensive testing to replicate the visual appearance of the original building, including reflection patterns at different times of day. The work included spectral analysis of glass types to identify viable formulas, computer model simulation, and, ultimately, a full-scale mockup tested on the UN grounds.

The original curtain wall was demolished and replaced with a pressure-equalized system in sections, proceeding from bottom to top in each 10-story zone between the louvered mechanical levels. Unlike the original curtain wall, which had been attached to the concrete floor slabs, the new system is connected to the now-reinforced building frame via outrigger plates. To mimic the appearance of the original double-hung windows, the team strategically offset some of the aluminum extrusions. The new cladding incorporates performance enhancements, such as low-E coating and blast protection.

The new open floor plan challenges the closed culture propagated by the original cellular offices. Significantly more light and air now enter the interior. The open plan also affords more flexibility and efficient use of space in a rapidly growing organization; the Secretariat now serves 193 member-states, as compared to the original 50.

The open-plan daylighting scheme includes 1,981-millimeter-tall furniture-work walls that extend from perimeter columns, without blocking natural light. The ceiling is 2.4 meters high but gradually steps up to 2.9 meters at the windows, allowing for a circulation path around the core, while supporting the equitable distribution of mechanical services. Seventy-five percent of workspaces now have daylighting and views.

Overall, the resulting building is 50 percent more energy-efficient than it was before the renovation. Replacement was never an option due to the iconic nature of the tower; instead, the classic building was thoroughly renovated in place. In many ways, the Secretariat’s radical revitalization is more about rebirth than restoration.

CTBUH Awards & Distinctions

Best Tall Building Americas 2014 Award of Excellence

2014 CTBUH Awards

26 October 2015 | New York City

United Nations Secretariat: Renovation of a Modernist Icon

Michael Adlerstein shares his insights into how the United Nations Secretariat Building, an aging icon of Mid-century Modernism, was renovated to meet the security, efficiency...

26 October 2015 | New York City

Interview: Michael Adlerstein

Michael Adlerstein of United Nations Capital Master Plan is interviewed by Chris Bentley during the 2015 CTBUH New York Conference at the Grand Hyatt New...

06 November 2014 | New York City

2014 Awards - Session 1 Q&A

Dr. Peter Irwin, Founding Partner, RWDI Consulting Engineers, Michael Adlerstein, Assistant Secretary-General & Executive Director, United Nations Capital Master Plan, John Gering, Managing Partner, HLW...

06 November 2014 | New York City

Best Tall Building Featured Finalist: Modernist Optimism Reconfigured for a New Century: The UN Secretariat

When the multi-billion dollar renovation of the UN campus started, the Secretariat, which has never ceased to operate as a functional government building, was plagued...

06 November 2014 | New York City

Interview: U.N. Secretariat Building Retrofit

Thursday, 6th November 2014. Chicago, USA. Michael Adlerstein, United Nations Capital Master Plan & John Gering, HLW International, discuss the retrofit of the United Nations...

06 November 2014 | New York City

Monthly Video: U.N. Secretariat Building Retrofit

Thursday, 6th November 2014. Chicago, USA. Michael Adlerstein, United Nations Capital Master Plan & John Gering, HLW International, discuss the retrofit of the United Nations...

19 September 2012 | New York City

New Skins for Skyscrapers: Anticipating Façade Retrofit

The existing building stock in some regions accounts for nearly as much energy consumption and carbon emissions as the transportation and industrial sectors combined. Existing...