CTBUH FAQs

Questions about defining and measuring tall buildings
The CTBUH Criteria for Defining and Measuring Tall Buildings explains in detail many common questions regarding the height and categorization of tall buildings. These include…

What is a Tall Building?
What is a Super-Tall Building?
How is the height of a tall building measured?
What is the difference between a tall building and a telecommunications tower?
What is the difference between ‘single-function’ and ‘mixed-use’ tall buildings?
When is a tall building considered to be ‘completed’?
When is a tall building considered to be ‘topped out’?
When is a tall building considered to be ‘under construction’?
When is a tall building considered to be a ‘real’ proposal?
How is the structural material of a tall building defined?

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Was there any organization that ranked tall buildings prior to the Council doing it?
Before the Council, there was no organization that recorded and ranked building height. Newspapers and writers did their own research to establish rankings when needed, but no one apparently saw a need for an authoritative “official” height list. When the Council (and its predecessor, the IABSE-ASCE Joint Committee) was set up, recording and ranking building height was not even considered to be a part of its function.

What are the hundred tallest buildings in the world?
The CTBUH maintains a significant ‘tallest database’ outlining the tallest buildings in the world in a variety of categories (i.e. tallest buildings by region/country/city, tallest buildings by function, tallest buildings by structural material, historical and future tallest buildings, tallest buildings under construction, tallest proposed buildings, etc). The 100 tallest buildings in the world can be seen here. CTBUH tallest lists include buildings that are under construction. However, only buildings that are completed are officially ranked on CTBUH listings.

It is clearly obvious that the CN Tower is the tallest building in the world. Why does the Council not recognize it?
The CTBUH tallest lists only recognize buildings not towers. A tall 'building' can be classed as such (as opposed to a tower) and is eligible for the tallest lists if at least 50% of its height is occupied by usable floor area. Therefore our lists do not include structures such as telecommunications towers and viewing towers. For more on this, see here.

If the Sears Tower places a big pole on top of the building and calls it art, does that make it the tallest building in the world again? It seems that anyone can put a huge spire on top of building and make it the tallest in the world.
This issue is a long standing argument and one of the reasons the Council recognizes tall building height in four categories:

1. Height to Architectural Top
2. Highest Occupied Floor
3. Height to Top of Roof
4. Height to Tip

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However, it is ‘Height to Architectural Top’ that is the most widely utilized and is used to define the rankings of the 100 Tallest Buildings in the World. Here height is measured from sidewalk level of the main entrance to the architectural top of the building, including spires, but not including antennae, signage or flag poles. The late Dr. Fazlur Khan, who was the original engineer of the Sears Tower and also a former Chairman of the CTBUH, was involved in writing these definitions. He always reported the Sears Tower to be 1,450 ft high. As far as the antenna supports, Dr. Khan never reported them. The CTBUH Height Committee meets regularly to keep on top of this debate and to discuss how increasingly common non-orthogonal and sculptural skyscrapers are impacting on how tall buildings should be measured and categorized.

Questions about tall buildings in general

When looking at the listings of tall buildings, there is sometimes a large variation in the number of floors compared to the height of each building. Is there any general explanation for this variation?
The main reason is the difference in floor to floor heights in office and residential (or hotel) buildings. Most office buildings require increased floor to floor heights to accommodate significant services above suspended ceilings and below raised floors. As such, residential or hotel buildings very often have more floors than office buildings of the same height.

What is the difference between useable and rentable areas?
They are very similar, within a few percent of each other, but not identical. ‘Useable area’ includes public spaces such as corridors, elevator lobbies and restrooms that are shared by tenants. ‘Rentable area’ may include some or all of these spaces, depending on local custom.

Is the developer the same as the owner of a building?
The developer may, or may not, be the owner. Typically, the developer has some sort of financial stake – but that stake can range from a few percent to a full 100%.

If there is no general contractor listed for a building, but there is a construction manager listed does that mean there is no general contractor?
If there is a construction manager listed, there may or may not be a general contractor involved. It is reasonably safe to assume that if no general contractor is listed, that the construction manager is functioning as the general contractor.

Questions about the CTBUH

What is the CTBUH?
The Council on Tall Buildings and Urban Habitat (CTBUH) is the world’s leading body in the field of tall buildings, and the recognized source of information on tall buildings internationally. It is the arbiter of tall building height and determiner of the title of ‘The World’s Tallest Building’. A not-for-profit organization, the CTBUH is sponsored by architecture, engineering, planning, development and construction professionals. Founded in 1969, the Council’s mission is to disseminate best practice information on tall buildings and sustainable urban environments, to facilitate business exchange amongst the international tall building / built environment community, and to make the latest knowledge available to professionals in a useful form.

Why should I join the CTBUH?
You and your firm will benefit from its association with the only true multidisciplinary, international organization in the construction industry and the urban habitat.

1. You and your firm gains instant access to state-of-the-art building concepts through conferences and publications.
2. You and your firm receive recognition through participation in Council-sponsored international activities.
3. You and your firm can contribute to the world body of knowledge in your field through high visibility publications.
4. Your support puts your firm in touch with both current and future leaders in research and in practice. The Council is a leading networking resource in the building industry.
5. An investment in research today brings innovation, progress and competitiveness tomorrow.

Click here to download a membership brochure and find out more about becoming a CTBUH member. To see the organizations that are already members, click here.

How can I get more involved with the CTBUH?
The Council always welcomes volunteers - whether you are active professionally, still in college or retired. For example, we are currently looking for CTBUH Country Representatives to provide direct contact between professionals in their country or region and the Council. If you would like to get more involved with the CTBUH, please email info@ctbuh.org