Is allowable area for each floor or for the entire building?

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aagangchen

October 27, 2023 05:16

Many people are confused by the allowable area calculation. Is allowable area for each floor or for the entire building?

The answer is it can be for each floor OR for the entire building, depending on the situation:

For example, if you are using IBC section 506.2.3 to calculate the allowable area for a single-occupancy, multi-story building, the allowable area (Aa) you calculated using Equation 5-2 is for the entire building. If the building has 3 floors, then the Aa is the total areas of all 3 floors, NOT for each floor.

On the other hand, if you use IBC section 506.2.1, Equation 5-1, then the result is for one floor, and also for the entire building.

If you set the Sa for Equation 5-2 as 1, then Equation 5-2 becomes Equation 5-1.

See screenshots below.

Gang Chen, Author, AIA, LEED AP BD+C (GreenExamEducation.com)

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  Adam B March 30, 2026 19:15 (Edited March 30, 2026 19:16)

  Please note that Div 506.2.1-506.2.3 have since been updated from the IBC 2018 for IBC 2021+ in a more condensed format.  

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