June 2012

With the recent completion of two megatall telecommunication/observation towers – Canton Tower in 2010 and Tokyo Sky Tree earlier this year – it is an appropriate time to review these structures and explain why they are distinguished from buildings in the Council’s official tallest lists.

To be considered a “building” a project must achieve three milestones: 1) it must be complete, 2) it must be freestanding and, 3) at least 50 percent of its height must be occubiable space. While projects like Canton Tower and Tokyo Sky Tree are indeed complete, free standing and partially occupiable – making them distinct from many of the world’s other telecommunication structures – less than 50 percent of their height is occupiable and thus the projects cannot be considered “buildings.” The following is a study of the world's “supertall” (300m+) occupiable telecommunication & observation towers (referred  to as “occupiable T&O towers” in the study) – some 36 of which now exist in 23 countries around the globe.

Figure 1. The world’s 10 tallest occupiable T&O towers according to “Height to Tip,” with a purple highlight showing the location of occupiable space. In the background are the world’s 10 tallest buildings, for comparison. View Larger Notes: (1) Data accurate as of May 2012; (2) Data souce: The Skyscraper Center
Figure 2. Location and History of Supertall Occupiable Telecommunication/Observation Towers View Larger
What’s the Difference? To be officially recognized as a “building” or an “occupiable telecommunication/observation tower,”  a project must meet a number of criteria. Four categories of structures are displayed and described below.
Figure 3. Comparison of tower types (left to right): Tall Building, Occupiable Freestanding Structure, Freestanding Structure, Cable-Stayed Structure View Larger		Figure 4. Supertall (300m+) Occupiable T&O Towers (36 No.) View Larger

This article was originally featured in the CTBUH Journal 2012 Issue II and is also available as a PDF download (download the Tall Buildings in Numbers article).