Gross floor area vs gross building area

how is the gross floor area measured?
how is the gross building area measured?

The IBC says inside face of exterior walls, but some I’ve also seen outside face of exterior walls. Just wondering if exterior walls are included or not. Thanks!

Hi @potoczakhalle ! Thank you for your question.

Per 2021 IBC (see Section 202: Definitions):

Gross Floor Area is defined as “the floor area within the inside perimeter of the exterior walls of the building under consideration, exclusive of vent shafts and courts, without deduction for corridors, stairways, ramps, closets, the thickness of interior walls, columns or other features…”

Gross Building Area is defined as “the area included within surrounding exterior walls, or exterior walls and fire walls, exclusive of vent shafts and courts…”

Simply put - Gross Floor Area does not include exterior walls and Gross Building Area does include exterior walls.

I hope this helps! Please let me know if you have any other questions.

Happy studying!

Kiara Galicinao, AIA, NCARB
Black Spectacles

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