If a building is a mixed occupancy with a fire barrier, a single building area exists, but two fire areas are created. Therefore:
"¢ Area limitations depend on the ratio of the adjusted floor area of each occupancy to the allowable tabular area of that occupancy. The sum of the ratios must not exceed 1 in accordance with Section 508.3.3.2 of the IBC. The building area must comply with the following area ratio equation:
Adjusted Floor Area 1 + Adjusted Floor Area 2 = â‰¤1.0
Allowable Tabular Area 1 Allowable Tabular Area 2
"¢ Height limitations of a building are based on the height of the fire area of the occupancy of the space.
"¢ Automatic sprinkler requirements of Chapter 9 of the IBC are on a fire-area by fire-area basis.
Note: If a building is a mixed occupancy with a fire wall, two buildings and two fire areas are created. Therefore, height and area limitations, as well as automatic sprinkler requirements, apply to each building separately in accordance with, Section 705.1 of the IBC.
It, and the chart, are from 2006 Preforming nonstructural plan reviews. ICC bookstore
Allowable area, In each story, the building area shall be such that the sum of the ratios of the actual floor area of each occupancy divided by the allowable area of each occupancy shall not exceed one.
Sorry if I am being dense
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