Council on Tall Buildings and Urban Habitat
 

Height: The History of Measuring Tall Buildings


December 2009
Marshall Gerometta, CTBUH Database Editor


In the past 40 years the CTBUH has been the recognized arbiter on tall building height, and the body that determines the title of “The World’s (or Country’s or City’s) Tallest Building”. It maintains three definitions for measuring tall building height along with numerous definitions pertaining to tall building height, function, materiality, etc. (
click here to see all CTBUH definitions/criteria). Its official Height Committee was formed in 1993, but the function of determining height, data and “tallest” titles pre-dates this, with the creation of the first official “CTBUH 100 Tallest Buildings in the World” list first appearing in the 80’s and which is now published in numerous reference books and periodicals each year.

Of course skyscrapers had been in existence for almost 80 years before the Joint Committee on Tall Buildings (as the Council was first known) formed in 1969. The first skyscraper (acknowledged because of its use of a curtain wall construction on a steel frame) is generally accepted as the 1885 Home Insurance Building by architect William Le Baron Jenney in Chicago. Being the first skyscraper, it was also the first to claim the title of “World’s Tallest Building” at 55m (180ft). Next to claim the title was the World Building in New York in 1890, followed by the Manhattan Life Insurance Building in New York in 1894. Most of the early skyscraper designs had flat roofs or domes at the top of their structures and were measured from curb to the top of building, with flagpoles generally not included. So, there wasn’t too much to debate when it came to claiming the “World’s Tallest” title. Even in 1905 when the New York Times Building, New York, was completed at 111m (363ft) to the roof with 128m (420ft) including flagpole, it was not considered to be taller than the 119m (391ft) high Park Row Building (also located in New York), which had held the world’s tallest title since 1899.

Following the Park Row Building, the Singer Building in New York was next to claim the title of “World’s Tallest” in 1908. It was surpassed the next year by the Metropolitan Life Insurance Company Tower in New York in 1909. In 1913 the Woolworth Building was completed and would claim the title for the next 17 years (see figure 1 for diagram of all “World’s Tallest Buildings” to date).

Figure 1. Diagram of all buildings that have at one time claimed the title of “World’s Tallest Building”.
Click here to enlarge.

Things got interesting in 1929, when two buildings in New York competed neck and neck to surpass the Woolworth—the Bank of Manhattan and the Chrysler Building. The Bank of Manhattan topped out at 282.5m (927ft) while the Chrysler Building’s final height was planned at 281.9m (925ft). But just a few months after the Bank of Manhattan was completed, a spire was secretly assembled in the Chrysler Building’s dome and hoisted into place, bringing the total height to 319m (1,046ft) (see figure 2). The spire was considered an architectural element of the building, thus giving it the world’s tallest title over the Bank of Manhattan. The Chrysler Building only held the world’s tallest title for just less than a year however, when the Empire State Building was topped out at 381m (1250ft).

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Figure 2. The Chrysler Building took the title of “World’s Tallest Building” in 1930 due to its 37m (121ft) spire, which was secretly constructed inside the building and lifted into place.

After the Depression and World War II, most new skyscrapers used the “International Style”, which typically had an orthogonal form with flat roofs and no spires. Many of the new buildings did add radio and television antennas to their tops, but these were not included in the official heights of the buildings.

The Empire State Building held the world’s tallest title for 41 years until New York’s 1 World Trade Center took over at 417m (1,368ft) in 1972. But its title was short-lived when Chicago’s Sears Tower was completed in 1974 at 442m (1,451ft). There was some debate at the time that the 540m (1,772ft) Ostankino Tower in Moscow (1967) and the 553m (1,815ft) CN Tower in Toronto (1976) should be considered the world’s tallest building, but since they were basically communication towers with observation platforms and not buildings in a traditional sense, the CTBUH did not consider them contenders for the “World’s Tallest Building” title. Instead each was designated as “the world’s tallest self-supporting tower”.

Defining the Criteria
So what actually is the world’s tallest building in criteria terms? The answer to this question is perhaps not as simple as it might first appear. First of all, the issue of what actually constitutes a building needs to be addressed, and how is it measured? Early discussions between CTBUH founders such as Lynn Beedle, Fazlur Kahn and Leslie Robertson in the early 70’s after the completion of the Sears Tower in Chicago came up with some basic height criteria. Here are a couple of excerpts taken from the later 1986 CTBUH publication “Tall Buildings of the World”, based on these early discussions:

A “building” is considered to be a structure that is designed for residential, business or manufacturing purposes. An essential characteristic of a building is that it has floors. Height is measured from the sidewalk of the main entrance to the structural top of the building including penthouse and tower. Television towers, radio antennas and flagpoles are not included. On the other hand, a tower is included if it is enclosed as an integral part of the structure—the Chrysler Building, for example. The number of stories begins at street level, main entrance.

The incident that really brought the whole issue of height—and the Council on Tall Buildings and Urban Habitat’s Height Committee—to prominence, was the debate in 1996 between Petronas Towers Malaysia and the Sears Tower Chicago. With their decorative spires considered part of the architectural height (similar to the Chrysler Building some 70 years previously), the 452m (1,483ft) Petronas Towers took the title of the world’s tallest building away from the then holder Sears Tower by 9.7m (32ft) since the antennae of Sears at 519m (1,704ft) height were not included in its height measurement.

However, the twin Petronas Towers were only 379m (1,242ft) without the spires, which was much shorter than both the highest inhabitable floor and flat roof of Sears. Thus viewing the Petronas and Sears Towers side by side (or seeing them in diagrammatic form), it seemed that Sears Tower was much taller, since the two 77m (253 ft) TV antennas brought the total height to 519m (1704ft). At the April 1996 CTBUH Height Committee Meeting, it was decided that the spires should count in the official height of the Petronas Towers, thus giving it the world’s tallest title, but it was a decision that many (especially Chicagoans!) disagreed with.

Partly in response to this situation, the Council created a further three new height categories: highest occupied floor, highest roof and highest tip of antenna, but this did not necessarily settle the issue, since the architectural height (including spires but not antennae) was the one that determined the world’s tallest title. This decision on Petronas versus Sears brought international attention in the news media since this was the first time a country outside the United States had held the world’s tallest building.

The Sears Tower still held the titles of highest floor (436m/1,431ft) and highest roof (442m/1,451ft), while 1 World Trade Center, New York held the highest antenna title at the time at (527m/1,728ft)

Post-Petronas
Things transitioned again in 2004 with the completion of Taipei 101, Taiwan, which became the world’s tallest building at 509m (1,670 ft), beating the Petronas Towers by 57m (187ft). A meeting of the CTBUH Height Committee convened in March that year recognized Taipei 101 with the world’s tallest title, along with the highest occupied floor (438m/1,440ft) and highest roof (448m/1,473 ft). There was still some disgruntlement from the US though, as the Sears Tower antennae were still higher than the spires of both Petronas and Taipei 101, at (527m/1730ft—the western antenna had been extended in June 2000 by 8m/26ft). Sears had achieved the title of the “tallest to tip” through default in 2001, after the atrocious acts of 9/11 and the destruction of the World Trade Center towers, New York.

On 24th May 2007 the CTBUH held a Height Committee meeting at the Illinois Institute of Technology in Chicago with an international attendance of 27 (see figure 3), to debate further the robustness of the existing height criteria, especially in light of projects such as the New York Times Building, New York, which was due for completion soon after with an architectural spire which looked to all intents and purposes like an antennae (and in light of several other projects which had architectural spires which contained antennae). The complexity and emotive subjectivity of the issues were apparent however in that, after a full day of involved debate, no change to the criteria was agreed on. The following points found a majority preference at the meeting:

• That the existing official height criteria to the architectural top should remain in place.
• That the highest occupied floor should be a conditioned floor where people continually either work or live, thus including observation decks but excluding mechanical floors.
• That parapets and screenwalls should be included in the height.
• That signage and lettering should not count in the height.
• That 50% or more of the building’s height (i.e. the majority) needed to be occupiable space for it to be counted as a building, and thus structures such as the CN Tower should not be considered buildings.
• That a building should only be added to the official tallest list when it is (i) topped out structurally and architecturally, (ii) fully clad, and (iii) open for business, or at least partially open. This became the CTBUH official definition of a building’s “completion”.

On September 15, 2009 a sub-group of the CTBUH Height Committee held a meeting in Chicago, specifically to discuss the shortcomings of the existing criteria in response to the ground conditions at both Trump International Hotel & Tower  Chicago and the Burj Dubai (see figure 4). All four CTBUH height categories were currently worded: “Height is measured from the sidewalk level outside the main entrance to...” but this is problematic as the world of tall buildings is increasingly witnessing (as in the case of both Burj Dubai and Trump), multiple significant pedestrian entrances at differing levels.

. CTBUH Height Committee discusses the height criteria at the Trump Tower in Chicago

Figure 3. Height Committee meeting held on May 24, 2007 in Chicago

Figure 4. CTBUH Height Committee sub-group considers base condition of Trump Tower Chicago on September 15, 2009

As a result of that meeting, the full height committee passed the changes in wording to: “Height is measured from the level of the lowest, open-air, pedestrian entrance to...”. The height committee feels this will offer the protection from buildings including sub-grade basements, car parking etc in their height figure, whilst allowing buildings such as the Burj Dubai to be not penalized for having a lower but above-grade entrance which may not be considered “main” but allows people to enter and exit the building at that point nonetheless.

This change resulted in the Burj Dubai being measured from the office entrance, which is the lowest of 3 entrances (residential, hotel, office), and also resulted in Trump Tower being measured from the public riverwalk, from which residents can enter directly into the building, and the public can enter the retail elements which are contained within the tower footprint. Interestingly, it would also move the Trump Tower one up the tallest rankings at 423m (1,389ft), from 7th to 6th place, leap-frogging Jin Mao tower at 421m (1,381ft). Also in response to the changing designs and forms of tall buildings, the Height Committee has elected to discard its previous “Height to Roof” category. View the press release here.

Any argument on which is the world’s tallest building will be settled by late 2009/early 2010 when the Burj Dubai is completed. At over 800m (2,600ft) it will be the tallest man-made structure ever built and it will claim the tallest in all four CTBUH height categories (see figure 4). The Burj Dubai is expected to be more than 60% taller than the current world’s tallest building (Taipei 101)—a quite amazing feat.

To read all CTBUH Height Criteria click here.