Council on Tall Buildings and Urban Habitat

The Council on Tall Buildings and Urban Habitat (CTBUH) is an international body in the field of tall buildings and sustainable urban design. A non-profit organization based at the Monroe Building in Chicago, Illinois, United States, the CTBUH announces the title of "The World's Tallest Building" and is widely considered to be an authority on the official height of tall buildings. Its stated mission is to study and report "on all aspects of the planning, design, and construction of tall buildings." The CTBUH was founded at Lehigh University in Bethlehem, Pennsylvania in 1969 by Lynn S. Beedle, where its office remained until October 2003 when it relocated to the Illinois Institute of Technology in Chicago. List of tallest buildings and structures The CTBUH ranks the height of buildings using three different methods: Height to architectural top: This is the main criterion under which the CTBUH ranks the height of buildings. Heights are measured from the level of the lowest, significant, open-air, pedestrian entrance to the top of the building, inclusive of spires but excluding items such as flagpoles and antennae. Highest occupied floor: Height to the floor level of the highest floor that is occupied by residents, workers or other building users on a consistent basis. Height to tip: Height to the highest point of the building, including antennae, flagpoles, and technical equipment. A category measuring to the top of the roof was removed from the ranking criteria in November 2009. This is because flat-topped skyscrapers are not as common in the modern era, as skyscrapers with intricate spire designs and parapet features atop their roofs make it more difficult to define the roof of a building. The CTBUH insist 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".