Mezzanine: 1/3 of room

[Ryan Schultz]

I think i might now the answer to this, but just wanted to verify.

For mezzanines, can you only take one-third of the floor area of that room that is open to the mezzanine?

That is, per the illustration below, we could only take 1/3(B) and not 1/3(B+C), correct?

 

[classicT]

1/3 of B - limited to not greater than 1/3 of the floor area of that room or space in which they are located. 2015 IBC 505.2

 

[Yikes]

2015 IBC 505.2.1 has exceptions that allow for larger mezzanines than that:

505.2.1 Area limitation. The aggregate area of a mezzanine or mezzanines within a room shall be not greater than one-third of the floor area of that room or space in which
they are located. The enclosed portion of a room shall not be included in a determination of the floor area of the room in which the mezzanine is located [Ryan Schultz: NO to A=1/3(B+C). YES to A=1/3B]. In determining the allowable mezzanine area, the area of the mezzanine shall not be included in the floor area of the room.
Where a room contains both a mezzanine and an equipment platform, the aggregate area of the two raised floor levels shall be not greater than two-thirds of the floor area
of that room or space in which they are located.

Exceptions:

1. The aggregate area of mezzanines in buildings and structures of Type I or II construction for special industrial occupancies in accordance with Section 503.1.1 shall be not greater than two-thirds of the floor area of the room.
2. The aggregate area of mezzanines in buildings and structures of Type I or II construction shall be not greater than one-half of the floor area of the room in buildings and structures equipped throughout with an approved automatic sprinkler system in accordance with Section 903.3.1.1 and an approved emergency voice/alarm communication system in accordance with Section 907.5.2.2.​