Appeal 34857

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. 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 not be greater than two-thirds of the floor area of the room.
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. The aggregate area of a mezzanine within a dwelling unit that is located in a building equipped throughout with an approved automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2 shall not be greater than one-half of the floor area of the room, provided that:

o Except for enclosed closets and bathrooms, the mezzanine shall be open to the room in which such mezzanine is located;
o The opening to the room shall be unobstructed except for walls not more than 42 inches in height, columns and posts, and;
o Exceptions to Section 505.2.3 shall not be permitted.

Allow a mezzanine with a floor and sloped seating to be considered a mezzanine using an area calculation method that incorporates the performance platform and open ground floor area that is in the same atmosphere as the mezzanine.

The proposed venue is a 2-story with mezzanine 52,458 s.f. fully sprinklered building of Type II-B construction with a platform for performances. 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 upper sloped seating area over occupied area below and the open to room area to include lower seating, not over occupied area, the opening to the ground floor and the performance platform, see attached plan and section. Equivalent protection for mezzanine occupants is provided by 2 enclosed exit stairways accessed directly from the mezzanine level and excess ceiling height above the path of egress.

The proposed calculation of the mezzanine meets the definition of mezzanine in OSSC Section 202.1 and the calculation method for area of OSSC 505.2.1, exception 2.

The definition of mezzanine is “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 in blue is an intermediate level between the second floor and the ceiling/roof.

The proposed mezzanine meets the parameters of OSSC 505.2 as having a clear height above and below the mezzanine floor of not less than 7 feet. It also meets the parameters of 505.2.1.1 for aggregate area, 505.2.2 for means of egress with 2 enclosed exit stairways, and 505.2.3, exceptions 2 and 5, for openness, for a mezzanine with access to two exits and sprinklered per OSSC 903.3.1.1.

The code commentary for Section 505.2.1 states that “The area may consist of multiple mezzanines open to the same room at the same of different levels, provided that the aggregate area does not exceed…” The commentary makes clear that a mezzanine area is calculated based on the area of the room, and could apply to multiple levels. This clarifies that area limitation calculated in 505.2.1 allows the calculation to be based on the room it is in, not a particular floor, the entire room. This supports the proposed design calculation method for area to include all areas that are directly open to the mezzanine level.

The proposed mezzanine is calculated as shown on the attached plan, showing that the mezzanine is calculated based on the room it is open to. Based on the section, there are portions of the ground floor and second floor that could be used in the calculation, but are not included in the open room. These spaces meet the requirements and intent of the code in that any fire/smoke event in this area would be readily seen by occupants on the mezzanine and they would react quickly and with intent as they would see smoke. This is made clear in the code commentary where it says “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.”

This interpretation is also reflected in the ICC opinion, attached, which clarifies that the proposed design meets the definition of mezzanine and that the calculation method shown in the attached drawings is a compliant method of determining the allowed area of a mezzanine.

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

The proposed design will provide additional protection measures as follows:

• Smoke detectors at high roof.
• Smoke detectors in the Performance Lounge
• Smoke detectors in the mezzanine level offices
• Smoke detectors in the mezzanine level unoccupied space

The proposed mezzanine for the CEV building meets the definition of OSSC Section 202.1 for being an intermediate level between a floor and a ceiling/roof and meets the area limitation method of 505.2.1, exception 2 and 5, for being open to a room or space. Therefore, with the clarification from the ICC that this method is compliant to code, we request approval of this appeal.

Reconsideration:

The additional information requested is as follows and as documented in the attached analysis.

The mezzanine designation and area calculation is compliant with the definition of a mezzanine in OSSC 202 and compliant with all the requirements in OSSC Section 505.2 for a mezzanine. The ICC opinion confirms the compliance of the configuration as submitted. The smoke reservoir is simply an additional protection measure which provides an additional few minutes of egress time. The smoke calculations are based on the highest fuel load being on the performance platform. Other fuel loads are either low, the seating, or are enclosed by partitions and with typically lower fuel loads than the equipment on the performance platform.

The mezzanine only requires a 7’-6” ceiling height per OSSC 1208.2. The proposed mezzanine has a much higher ceiling. The mezzanine has 2 enclosed exit stairways and also has 4 aisles that provide an egress route to the second floor which also has two exit stairways. This is in excess of code requirements for a mezzanine.

The ICC opinion confirms that the proposed mezzanine calculation method, and therefore its designation as a mezzanine, is compliant with code requirements as a mezzanine. The proposed additional protection measures of a smoke reservoir and additional egress routes that mezzanines are not required to have, increase the protections for the occupants of the mezzanine. Therefore, we request approval of this appeal.