Council on Tall Buildings and Urban Habitat
Creating Industry-Accepted Criteria for Measuring Tall Building Floor Area
Project Start: September 2017
Anticipated Project Completion: September 2018
Funding Sponsor:
Principal Investigators:
Dario Trabucco, CTBUH; Antony Wood, CTBUH

CTBUH has received $90,000 in funding from ArcelorMittal to embark on an important 12-month research project, “Creating Industry-Accepted Criteria for Measuring Tall Building Floor Area.” This research aims to identify the aspects of existing codes and regulations that are internationally accepted and the areas where the code and regulations are contentious or are too broad. This is with the view of creating varying categories of CTBUH Floor Area Criteria, much like the CTBUH Height Criteria, to provide a clear method for accurately and concisely measuring a building’s GFA, NIA, NRA, etc. Not only will these new criteria provide a method to accurately measure floor areas, but they will complement CTBUH’s existing definitions and criteria surrounding tall buildings. 

Funding Sponsor

Project Milestones
2018, October: Research Results Presented at 2018 CTBUH Conference in Dubai
2018, September: Research Director Joins IPMS Meeting in Brazil
2018, March:
CTBUH Research Director Joins IPMS Standards Setting Committee
2017, October:
Introductory Video Presented to Delegates at the CTBUH Research Booth
2017, October:
Calculating Floor Areas in Skyscrapers Workshop at CTBUH 2017 Conference
2017, September:
CTBUH Meets with the IPMS Standards Setting Committee in London
2017, September: Research Project Starts

Depending on the building standards and regulations of various countries, measuring floor area varies dramatically. The most common method to measure a building’s floor area is by using Gross Floor Area (GFA); however, there are countless other methods, including Gross Internal Area (GIA), Net Internal Area (NIA), Gross Leasable Area (GLA), and Net Rentable Area (NRA), among others. GFA, in real estate, is generally considered to be the total floor area contained within a building’s envelope, measured to the external face of the external walls. That being said, due to a lack of specificity or internationally accepted standards, the measurement of floor area has been used interchangeably with other floor calculation methods, which may increase the floor area of a given building through the inclusion of corridors, walls, lift shafts, stairs, bathrooms, etc.

Furthermore, areas such as Hong Kong and Singapore include clauses in their building regulations to encourage the incorporation of green features on buildings. Although this is seen as a positive move, this leads to discrepancies with the definition of floor area compared to other countries. In some instances, building authorities have to determine how the floor area of a building is calculated on a case-by-case basis, due to the lack of specificity. Also, these differences between international standards are becoming increasingly problematic, due to multi-national investment scenarios happening in major cities all over the world. Now, the floor area demands of an international client may not reconcile with the floor area definitions of the host country. Like the internationally recognized method of measuring height that was created and refined by CTBUH, a standard for measuring floor area must now be developed.

The criteria will introduce an industry-accepted standard and will also provide further clarity for existing CTBUH Height Criteria definitions, including:

•    Building: A tall “building” can be classed as such (as opposed to a telecommunications or observation tower) and is eligible for the "Tallest” lists if at least 50 percent of its height is occupied by usable floor area. How is usable floor area measured?

•    Single-Function Building: A tall building is single-function when 85 percent or more of its total floor area is dedicated to a single use. Does total floor area refer to NIA, GFA, or something else entirely?

Examples of net and gross floor area in a high-rise.

This research will answer these questions by analyzing the methods, regulations, and requirements for measuring floor area in different countries. Furthermore, it will employ case studies to better understand how floor area has been calculated for buildings in the past according to the criteria of their respective polity.
The next phase of the research will compare the differences between the existing standards and regulations and, possibly more importantly, identify the aspects of calculating floor area that are already globally accepted. This part of the research will seek out a group of interdisciplinary external experts and ask for their definition of floor area, changes they would like to see made, and aspects of their country’s current system with which they agree or disagree. The consultation with these external experts will be conducted with the view of creating a CTBUH Floor Area Calculation Sub-Committee, which will serve a similar purpose to that of the CTBUH Height Committee.

Through the investigation of existing standards and continuous consultation with external experts, the research team will create an internationally accepted Floor Area Criteria. These new criteria will be distributed and disseminated through promotion at international tall building events. The research team will also apply the criteria to the tallest buildings in the world and implement the calculations onto The Skyscraper Center, the premier database for accurate, reliable information on tall buildings around the world.

This undertaking represents yet another CTBUH member-funded research project, which is an indication of the unmatched capacity of the Council to explore some of the most intricate, under-explored, and essential aspects of tall building design.

Contact Information
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