Appeal 34843

2022 OSSC 505.2.1

505.2.1 Area limitation. The aggregate area of a mezzanine or mezzanines within a room shall not be greater that 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. In determining the allowable mezzanine area, the area of the mezzanine shall not be included in the floor area of the room.

Exceptions:

1. Not used.
2. The aggregate area of mezzanines in buildings of Type I or II construction shall not be 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 approved emergency voice/alarm communication system in accordance with Section 907.5.2.2.
3. Not used.

Allow a mezzanine with a floor and stepped seating, incorporating the area of the mezzanine over the second floor with stepped seating and the open ground floor area and performance platform which is open to the same atmosphere.

The proposed venue is a 2-story 52,458 s.f. fully sprinklered building of Type II-B construction with a performance platform and mezzanine. The ground floor is for standing audience, open to the second floor seating and mezzanine seating above. The building will be equipped with an emergency voice/alarm communication system.

The proposed design is for the mezzanine area calculation to be based on OSSC 505.2.1, exception 2 with a mezzanine starting at a point in the sloped seating area over occupied area below, Level 2 seating, open ground floor and performance platform (see attached floor plans and sections). The area is calculated as shown on the attached mezzanine calculation study based on the area below that it is open to and shares the same atmosphere.

Equivalent protection for mezzanine occupants is provided by direct access to two enclosed exit stairways and excess ceiling height above the path of egress.

The proposed mezzanine meets the calculation method for area of OSSC 505.2.1, exception 2, and the definition of mezzanine, “An intermediate level or levels between the floor and ceiling of any story and in accordance with Section 505.” The mezzanine shown in the attached plan and section is an intermediate level between the second floor and the ceiling/roof. The proposed mezzanine complies with OSSC 505.2 requirements:

• Clear height above and below the mezzanine floor of not less than 7 feet (505.2)
• Area not greater than one-half of the floor area of the room equipped with automatic sprinkler system and approved voice/alarm communication system (505.2.1, exception 2)
• Aggregate area requirements (505.2.1.1)
• Means of egress requirements with two enclosed exit stairways (505.2.2)
• Openness requirements for a mezzanine with access to two exits and sprinklered per OSSC 903.3.1.1 (505.2.3, exceptions 2 and 5)

The code commentary for Section 505.2.1 supports calculating the mezzanine based on the area of the room it is in, not a particular floor. As shown on the section and the mezzanine calculation study area shown in blue, there are portions of the ground floor and second floor that are atmospherically connected but are not included in the area calculation. These spaces meet the requirements and intent of the code in that a fire/smoke event in this area would be readily seen by occupants on the mezzanine and they would react quickly with intent.

The intent is clarified in the commentary, “Because of a mezzanine’s restricted size and its required openness to the room or space in which it is located, a mezzanine is not considered to contribute significantly to a building’s inherent fire hazard.” It is also reflected in the attached ICC-online staff opinion, which confirms that the proposed design meets the definition of mezzanine and that the calculation method shown in the drawings is compliant.

The proposed mezzanine consists of seating that are compliant with NFPA 260 and Cal 117, to resist ignition, non-combustible flooring in aisles and exit accessways as required by OSSC Chapter 8, restrooms that have a very low fuel load, and offices for security and maintenance staff. The proposed uses provide lower fuel load and fewer ignition sources than the mezzanine provisions were originally considered for, which was for the storage of materials in an industrial use, or an office use with typical fuel load and ignition source of paper.

The proposed design will provide additional smoke detectors in the following locations:
• At the high roof
• In the performance lounge
• In the mezzanine level offices
• In the mezzanine level unoccupied space

The volume of space above the mezzanine level provides an area where smoke can accumulate, providing additional time for occupants to egress unimpeded from the mezzanine level.

The proposed mezzanine meets the definition of OSSC Section 202.1 and the area limitation method of 505.2.1, exceptions 2 and 5. With the ICC code commentary and online staff opinion confirming that this method is compliant to code, we request approval of this appeal.