Use and Occupancy Classification

Use and Occupancy Classification

Classifies every building and space by occupancy group based on the way it is used and the relative hazard to occupants — the foundation for nearly every other code requirement.

301 — General

The provisions of this chapter shall control the classification of all buildings and structures as to use and occupancy. Each building or portion thereof is classified into one or more of the occupancy groups defined in this chapter according to its nature and the hazards to occupants. See Section 302 for the full list of occupancy groups. The classification assigned here drives requirements throughout the code, including the height and area limits in Chapter 5 and the egress provisions in Chapter 10.

302 — Occupancy Classification and Use Designation

Structures or portions of structures are classified with respect to occupancy into one or more of the groups listed below. A space, room, or area is to be classified by the use that most nearly resembles its actual occupancy. Where a structure is proposed for a use not specifically listed, its classification is determined by the building official based on the most similar listed occupancy.

• Assembly (Groups A-1, A-2, A-3, A-4 and A-5) — see Section 303
• Business (Group B) — see Section 304
• Educational (Group E) — see Section 305
• Factory and Industrial (Groups F-1 and F-2)
• High Hazard (Groups H-1, H-2, H-3, H-4 and H-5)
• Institutional (Groups I-1, I-2, I-3 and I-4)
• Mercantile (Group M)
• Residential (Groups R-1, R-2, R-3 and R-4)
• Storage (Groups S-1 and S-2)
• Utility and Miscellaneous (Group U)

The ten occupancy groups defined in Section 302.

Worked example

Scenario: A developer is fitting out a 3,500 sq ft ground-floor space as a sit-down restaurant with seating for 120 guests.

Explanation: Because more than 50 occupants gather to consume food and drink, the space is classified Assembly Group A-2 (see Section 303), not Business Group B. That single decision raises the bar on egress, occupancy load, and fire-resistance requirements for the rest of the project — which is why occupancy is the first thing to lock down.

303 — Assembly Group A

Assembly Group A occupancy includes, among others, the use of a building or structure, or a portion thereof, for the gathering of persons for purposes such as civic, social or religious functions; recreation, food or drink consumption; or awaiting transportation.

Small assembly spaces and certain accessory religious or community uses may be classified as Group B under Section 304 where the occupant load and area fall below the stated thresholds.

304 — Business Group B

Business Group B occupancy includes the use of a building or structure, or a portion thereof, for office, professional or service-type transactions, including the storage of records and accounts. Examples include banks, professional services, outpatient clinics, and educational occupancies for students above the 12th grade.

305 — Educational Group E

Educational Group E occupancy includes the use of a building or structure, or a portion thereof, by six or more persons at any one time for educational purposes through the 12th grade. Religious educational rooms and auditoriums with an occupant load of less than 100 per room or space and accessory to a place of worship are classified as Group A-3.

Frequently asked questions

What occupancy group is a restaurant under IBC 2015?

A typical sit-down restaurant with an occupant load of 50 or more is classified as Assembly Group A-2 under Section 303. Smaller spaces below the threshold may fall under Business Group B (Section 304).

Can one building have more than one occupancy classification?

Yes. Section 302 allows a building to contain multiple occupancy groups. Mixed occupancies are then handled as separated or non-separated occupancies under the provisions referenced in Chapter 5.

Who decides the occupancy group for an unusual use?

Where a proposed use is not specifically listed, Section 302 directs the building official to assign the classification that most nearly resembles the actual use based on the relative hazard to occupants.

Templates

• Occupancy Classification Worksheet (2d) — A fillable 2D worksheet that walks each space in your project through the Section 302 decision tree to the correct occupancy group.
• Mixed-Occupancy Model Template (3d) — A starter 3D Frame model with occupancy groups pre-tagged per zone — drop in your geometry and Frame checks separation and area limits as you build.