The Accessory Coffee Bar and the Free Mezzanine
A developer proposes a two-story, 44,000 sq ft building (22,000 sq ft per floor) of Type VB construction, fully sprinklered, with a ground floor containing a 12,000 sq ft mercantile sales area, a 1,100 sq ft coffee bar with 44 fixed seats and a 12 ft service counter with standing room in front of it, a 4,000 sq ft management office, and the balance in circulation and support. Above the sales area the architect shows a 5,000 sq ft mezzanine reached by two open stairs and used for seasonal displays. The narrative states that the coffee bar is 'accessory,' so no separation is required and it may simply be labeled Group M; that the mezzanine is not a story because it is open to the sales floor; and that the two open stairs are adequate for egress.
1. Is the coffee bar properly classified as Group M accessory space? Show how the occupant load drives the answer.
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The label cannot be accepted without computing the occupant load first.
- Classification. A cafe or restaurant is Group A-2 assembly. Two off-ramps exist: the accessory-occupancy rule (a space ancillary to the main occupancy, occupying not more than 10 percent of the story's floor area, may be classified as part of the main occupancy without separation) and the small-assembly rule (an assembly room with an occupant load under 50 may be classified as Group B or as part of the primary occupancy).
- Area test. 1,100 / 22,000 = 5 percent, so the accessory area cap is met. That alone does not settle it.
- Occupant-load test. The designer counted only the 44 seats. Standing space at the counter must be counted at 5 net sq ft per occupant. If the standing zone is, say, 120 sq ft, that is 24 more occupants, for a total of 68. An occupant load of 50 or more defeats the small-assembly allowance, and the space must be classified A-2.
- Even if it stays accessory, the occupant load of the coffee bar is added to the story's load for egress calculations and for the width of the exits it uses. Accessory status affects separation, not egress math.
- If it is A-2, the project must either provide the required separation from the M and B spaces or comply with the nonseparated mixed-occupancy provisions, in which case the building's height, area and fire protection must satisfy the most restrictive occupancy in the mix.
2. Is the 5,000 sq ft mezzanine a story, and does its openness eliminate the need for additional exits?
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It is a story, and openness to the room does not satisfy egress.
- Story test. A mezzanine is not counted as a story only where it is not more than one-third of the floor area of the room in which it is located. Here 5,000 / 12,000 = 41.7 percent, which exceeds one-third. It counts as a story. Reducing it to 4,000 sq ft or less would keep it out of the story count.
- Aggregate cap. The combined area of mezzanines within a room also may not exceed one-half of the floor area of that room; at 41.7 percent this one is within that cap, but any second mezzanine over the same sales floor would have to be counted against it.
- Height and area. Because the mezzanine is a story, the building's allowable number of stories and area must be rechecked against the tabulated limits for Type VB at the adopted edition, including any sprinkler and frontage increases. The building cannot be described as two stories.
- Egress from the mezzanine. The mezzanine occupant load is computed on its own floor area (mercantile at 60 gross gives roughly 83 occupants for 5,000 sq ft). That exceeds the one-exit limit for a space, so two means of egress are required, separated by at least one-half of the diagonal of the mezzanine area, reduced to one-third where the building is sprinklered. Two open stairs can work, but only if the separation dimension is satisfied, the stairs are permitted to be unenclosed in a sprinklered building, and each stair has the required capacity.
3. If the applicant insists on keeping the 5,000 sq ft mezzanine, what has to change in the analysis?
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The whole building analysis is reopened.
- Story count. Recheck allowable stories for Type VB with each occupancy at the adopted edition. If the count is exceeded, the options are: shrink the mezzanine to one-third of the room area or less, upgrade the construction type, or introduce a compliant separation.
- Area. Recompute the building area including the mezzanine floor area, apply the mixed-occupancy rules that match the approved classification of the coffee bar, and apply sprinkler and frontage increases only to the extent the tables allow.
- Separation. Either provide the required separation between A-2, M and B spaces, or demonstrate compliance under the nonseparated mixed-occupancy provisions where the most restrictive occupancy governs the height, area and fire protection of the whole building.
- Egress. Add the mezzanine occupant load to the story load, verify stair and door capacity, verify the one-half or one-third diagonal separation between the two stairs, and verify that the open stairs meet the conditions under which unenclosed exit access stairways are permitted.
The code official's action is a disapproval with specific deficiencies, not a rejection of the project: each item above can be cured, but none of them can be cured by relabeling the spaces.