Hi, this might be a basic question, but I’d like to clarify something that’s been confusing me.
In IBC Table 506.2, if there is no frontage increase available for a project (i.e., the frontage area factor increase is zero), does the “Allowable Area Factor” listed in Table 506.2 refer to the ‘floor area per individual floor’, or the ‘overall total floor area of the building’?
Welcome to the ARE Community, @giyoungoh! Thank you for writing in with your question.
This is definitely a common area of confusion, so you are not alone.
Regardless of a frontage increase, IBC Table 506.2 provides an allowable area factor, which is then used to calculate the allowable area of a building using one of the formulas provided in 506.2.1 Single-occupancy buildings: Equation 5-1 (maximum of 3 stores above grade) or Equation 5-2 (more than 3 stories above grade).
Equation 5-1 provides the allowable area per story, while Equation 5-2 provides the total allowable area for the building.
Hope this helps!
Kiara Galicinao, AIA, NCARB
Black Spectacles
Thank you so much! How about (Equation 5-3) in IBC 2018? Is it area per floor or total area?
Also I’m wondering which code version I should refer to for the exam this year—2018 or 2021? I’ve noticed a significant difference in Chapter 5.
@giyoungoh Equation 5-3 (mixed-occupancy buildings) provides the allowable area per story. Note that there are additional guidelines for buildings with more than 3 stores above grade. See Section 506.2.2.
As of February 27, 2024, the ARE references the 2021 IBC and other ICC family of codes/standards. See page 118 of the ARE 5.0 Guidelines for a list of code versions that the ARE currently references.
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