ELLEN09US:
Please explain what is driving your question. Usually there is not an issue with floor areas unless you are dealing with a planning/zoning limit on home area vs. lot size.
Is the "plan checker" building or planning?
The CA residential code does not define floor area, here is the res code reference for terms defined in other CA codes:
R201.3 Terms defined in other codes. Where terms are not
defined in this code such terms shall have meanings ascribed
to them as in the California Building Standards Code, Title
24, California Code of Regulations.
Here is the CBC for floor area, gross and net:
FLOOR AREA, GROSS. The t100r 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, closets, the thickness of interior
wans, columns or other features. The floor area of a building,
or portion thereof, not provided with surrounding exterior
walls shall be the usable area under the horizontal projection
of the roof or floor above. The gross floor area shall not
include shafts with no openings or interior courts.
FLOOR AREA, NET. The actual occupied area not including
unoccupied accessory areas such as corridors, stairways,
toilet rooms, mechanical rooms and closets.