One of the first tasks an architect is to do when determining the code requirements is to establish the occupancy group of a space. A building may have a single occupancy group if it has a singular purpose, provided that the ancillary space spaces, such as conference rooms and break rooms, fall within the provisions of accessory occupancies. Typically, many modern buildings have multiple occupancy groups. This could include an office space with a large assembly space for employee training, a mixed-use podium building with retail and parking below residential and amenity spaces above a concrete deck or even a more complicated structure such as a hospital which may have many occupancy groups within the structure.
Purpose of the Space
The first place to start in determining the occupancy group is to think about the “purpose” of the building or space.Section 302.1 states that the occupancy group is a formal designation of the purpose of a building. The dictionary defines “purpose” as the reason for which something is done or created or for which something exists. How would the space, building or structure be described in a few words, if you were to stop people on the street and poll them? A high school isn’t “an educational institution for 9-12 grade” to most people, if you were to ask them… it’s called a “high school”, or just simply “school”, and most people understand what that entails. The purpose of a building is to be a “school”. The school board sells bonds for the purpose of constructing a “school”. Education (the verb and noun) is what we all hope happens within.
However, the requirement to establish an occupancy group applies to the individual spaces that make up the building. Even though there may be a “School”, it likely also has a gymnasium and perhaps a cafeteria or everyone’s favorite: the “Cafetorium”. Each of these spaces should be analyzed separately with it’s own occupancy group provided. Multipurpose spaces such as our ‘cafetorium’ are required to be analyzed for the most restrictive requirements of each. In code terms, it must “comply with all applicable requirements…”.
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Other buildings may have multiple “purposes”, such as a car dealership. These buildings have both areas for car sales and typically a repair garage adjacent or part of the same building.
Selection of Occupancy Groups
To select the proper occupancy group, first understand the use and how the user intends and plans to use the spaces involved. Properly understanding the needs of the client at the beginning will help understand the use of the space in question. While it’s unlikely to confuse a conference room with a hazardous materials storage room, confusion may occur in determining exactly which occupancy group is most appropriate. Is a nursing home an I-1, I-2, R-4 or something else? Unless we work doing the same project time often, we likely won’t remember the variations between an E, an I-4 or an R-3 day care facility. Some of these occupancy groups are based on the occupant load or maybe the number of people served. A larger conference room may be an A-3, while a slightly smaller conference room is required to be a B occupancy in some states, and may optionally be a B occupancy in other states. To correctly apply the correct occupancy group requires sitting down with the code and properly analyzing the building and it’s individual spaces.
Another tool available is the UpCodes Occupancy Guide. This tool guides you through a series of questions to help you find the occupancy group, and to inform the user as to why it is a particular occupancy group.
State Specific Occupancy Groups
Not only can various occupancy groups be confusing, another layer of state regulations and building code amendments in some states can become more confounding. Some states such as California, have added a number of occupancy groups to address specific state requirements promulgated by various agencies. These include deletion of I-1, addition of I-2.1, R-2.1, R-2.2 and R-3.1. In addition, various thresholds for uses such as day-cares can be adjusted to meet state licensing requirements. Here again, the Occupancy Guide by UpCodes can provide direction in deciding which occupancy group is most appropriate.
Occupancy Classifications: Past and Present
Before we had the more commonly known occupancy group designations of A, B, E, I etc., the occupancy designations were labeled A - J with relative risk based on occupancy ranked from highest (A) to lowest (J). While this gives a general idea of risk to large numbers of occupants, it was not descriptive and did not rank hazardous facilities with a high level of risk. It becomes problematic when a change of occupancy is proposed to a building that was originally permitted under these old occupancy groups. If the original permit or certificate of occupancy stated a B-2, that would not therefore be a Group B occupancy under the current code, but likely an A-3 occupancy.
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* Always consult with a hazardous materials specialist or fire protection engineer when considering occupancies related to hazardous materials.
** H-4 and H-5 consider toxic materials and materials related to semiconductor fabrication, and do not have a direct correlation with the 1973 building code.
Please note we’ve used the Wyoming Building Code for the examples above as it shares much in common with many other state and city codes. Please reference your jurisdiction’s codes for amendments specific to your project.