Definition of "world's tallest building" updated

The new criteria wording—“Height is measured from the level of the lowest, significant, open-air, pedestrian entrance to…” allows for the recognition of the increasing numbers of multi-use tall buildings with often several different entrances at different levels, whilst also accommodating buildings constructed in non-traditional urban or suburban locations. The CTBUH Height Committee has determined that the previous description of where to measure tall building height from—“Height is measured from thesidewalk outside the main entrance to…” is now no longer sufficient.

This will have an impact on both the height of tall buildings and their relative international height rankings. Burj Dubai, set to open as the world’s tallest building in January 2010, will now be measured from the lowest of its three main entrances (which opens into the entrance lobby for the tower’s corporate suite office function), while the recently completed Trump International Hotel & Towers in Chicago will be measured from the lower, publicly accessible Chicago Riverwalk. In the case of Trump, this additional 27 feet means that it will surpass the Jin Mao Tower in Shanghai to occupy the rank of 6^th tallest on the current list of completed buildings.

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. “The roof category just doesn’t make sense anymore,” said CTBUH Executive Director Antony Wood.  “In the era of the flat-topped modernist tower, a clearly defined roof could usually be identified, but in today’s tall building world—which is increasingly adopting elaborate forms, spires, parapets and other features at the top of the building—it is becoming difficult to determine a ‘roof’ at all, even less so to measure to it.”

The revised CTBUH Height Criteria and diagrams of the tallest 10 buildings in the world as of November 2009 can be found at criteria.ctbuh.org, ranked according to the three height categories now recognized by CTBUH. These are:

(i) Height to Architectural Top, measured to the topmost architectural feature of the building including spires, but not including antennae, signage, flag poles or other functional-technical equipment

(ii) Height to Highest Occupied Floor, measured to the level of the highest, consistently occupied floor in the building (not including service or mechanical areas which experience occasional maintenance access)

iii) Height to Tip, measured to the highest point of the building, irrespective of material or function of the highest element.