804.15  APPLICABLE FLOOR AREA.
   Floor area shall be calculated as defined in this chapter.  Total floor area applicable for the determination of the yearly regulatory fee shall include the sum total of all the floor area in use or reserved or retained for the use of the commercial establishment, including, but not restricted to, principal and accessory floor area, cellars and basements, and storage or detached accessory buildings, even though any such floor area may be temporarily vacant or not in use.