Section 3.01.03:. Mixed Occupancy

1. General. When a building is used for more than one occupancy purposes, each part of the building comprising a distinct "Occupancy" shall be separated from any other occupancy. When a building is used for more than one occupancy purpose, it shall be subject to the most restrictive requirements for the occupancies concerned: Except, — (1) When a one-story building houses more than one occupancy, each portion of the building shall conform to the requirements for the occupancy housed therein, and the area of the building shall be such that the sum of the actual areas divided by the allowable area for each separate occupancy shall not exceed one; and (2) Where minor accessory uses do not occupy more than 10 per cent of the area of any floor of a building, nor more than 10 per cent of the basis are permitted in the occupancy requirements. The major use of the building shall determine the occupancy classification provided the uses are separated in accordance with requirements for occupancy separation.

2. Forms of Occupancy Separation. Occupancy separations shall be vertical or horizontal or both, or when necessary, of such other form as may be required to afford a complete separation between the various occupancy divisions in the building.

3. Types of Occupancy Separation. Occupancy separations shall be classed as "One-Hour Fire-Resistive" "Two-Hour Fire-Resistive", "Three-Hour Fire-Resistive", and "Four-Hour Fire-Resistive".

   1. A "One-Hour Fire-Resistive Occupancy Separations" shall be of not less than one-hour fire-resistive construction. All openings in such a separations shall be protected a fire assembly having a one-hour fire-resistive rating.

   2. A "Two-Hour Fire-Resistive Occupancy Separation" shall be of not less than two-hour fire-resistive construction. All openings in such separation shall be protected by a fire assembly having a one and one-half-hour fire-resistive rating.

   3. A "Three-Hour Fire-Resistive Occupancy Separation" shall be of not less than three-hour fire-resistive construction. All openings in walls forming such separation shall be protected by a fire assembly having a three-hour fire-resistive rating. The total width of all openings in any three-hour fire-resistive occupancy separation wall in any one-story shall not exceed 25 per cent of the length of the wall in that story and no single opening shall have an area greater than 10.00 square meters (107.1 square feet). All openings in floors forming a "Three-Hour Fire-Resistive Occupancy Separation" shall be protected by vertical enclosures extending above and below such openings. The walls of such vertical enclosures shall be of not less than ten-hours fire-resistive construction, and all openings therein shall be protected by a fire assembly having one and one-half-hour fire-resistive rating.

   4. A "Four-Hour Fire-Resistive Occupancy Separation" shall have no openings therein and shall be of not less than four-hour fire-resistive construction.

4. Fire Ratings for Occupancy Separation. Occupancy separations shall be provided between various groups, subgroupings, or divisions of occupancies. The Secretary shall promulgate rules and regulations for appropriate occupancy separations in buildings of mixed occupancy: Provided, That where any occupancy separation is required, the minimum shall be a "One-Hour Fire-Resistive Occupancy Separation"; and where the occupancy separation is horizontal, structural members supporting the separation shall be protected by equivalent fire-resistive construction.