When starting any design of new building construction or even a renovation one of the first steps is to determine the building’s Occupancy Classification.  This is very important because each classification has specific Dos, Don’ts, and regulations specific to the classification and groups.  The code uses Occupancy Classifications, which represent varying levels of hazard and risk to building occupants and adjacent properties, to classify buildings by their primary use and purpose.  In this post, we will assume your local jurisdiction has adopted the International Building Code (IBC) as it is the most popular model code in the USA and adopted in many countries worldwide.  The IBC organizes and categorizes buildings into 10 main Occupancy Classifications and when you consider subgroups there is a total of 26 groups.

For many buildings, it can be quite easy and straightforward to determine the building’s Occupancy Classification.  You simply go to the IBC Chapter 3 and find the building group listing that most closely matches your building’s usage.  For example if you are planning to design and build an office building then you would find that Section 304 “Business Group B” includes buildings uses for office, professional, or service-type transactions.  Similarly if you are planning a hotel you would find under section 310, “Residential Group R” specifically list Hotels and Motels as Residential Group R-1. 

ICC provides FREE access to all of their model codes. See our post for free links to all of the ICC codes such as IBC, IRC, IEBC, etc.

Why does the IBC have Occupancy Classifications?

The International Building Code (IBC) uses the occupancy group classifications to ensure buildings are designed and built to appropriate safety standards.  The occupancy classifications are grouped primarily based on their relative fire hazard and life safety properties such as how many people will be in the area, are there hazardous materials or manufacturing, and are people sleeping, cooking, living etc.  The rest of the codebook uses the occupancy classification to organize requirements like allowable building height, appropriate types of construction as well as occupant safety requirements such as means of egress, fire protection systems, fire rated wall separations and devices.

All Occupancy Groups and Examples

The information provided below is for general use only, additional information is available in the International Building Code specifically Chapter 3 Use and Occupancy Classifications.  You should also consult your Local Building Official or a Design Professional in determining the appropriate Classification for your situation.

Occupancy Classification	Examples
Assembly Group A-1	Movie Theaters, Concert Halls
Assembly Group A-2	Restaurants, Bars, Cafeterias
Assembly Group A-3	Churches, Gymnasiums, Libraries
Assembly Group A-4	Arenas, Indoor Swimming Pools
Assembly Group A-5	Outdoor Stadiums
Business Group B	Offices, Colleges, Banks
Educational Group E	K-12 Schools, Daycare Facilities
Factory and Industrial Group F-1	Moderate-hazard Factories
Factory and Industrial Group F-2	Low-hazard Factories
High Hazard Group H-1	High-hazard Detonation
High Hazard Group H-2	High-hazard Accelerated Burning
High Hazard Group H-3	High-hazard Combustion
High Hazard Group H-4	High-hazard Health
High Hazard Group H-5	High-hazard Semiconductors
Institutional Group I-1	Assisted living, Halfway Houses (Greater than 16 occupancts)
Institutional Group I-2	Hospitals, Nursing Homes
Institutional Group I-3	Prisons, Detention Centers
Institutional Group I-4	Adult or Child care facilities
Mercantile Group M	Department or Drug Store, Markets
Residential Group R-1	Hotels, Boarding Houses
Residential Group R-2	Apartments, Dormitories, Live/ Work Units
Residential Group R-3	Single family homes, Duplex homes
Residential Group R-4	Assisted living, Halfway Houses (Between 5 and 16 occupants)
Storage Group S-1	Storage of Books, Furniture, Lumber
Storage Group S-2	Storage of Glass, Metals, Food
Utility and Miscellaneous Group U	Barns, Carports, Sheds

Below is much greater detail of each occupancy classification and more examples from the IBC.

Related Questions

What if my building does not match an exact Occupany Group Classification?

When a building’s usage purpose does not fit neatly into one of the prescribed groups the IBC tells us that the structure shall be classified “in the occupancy it most nearly resembles based on fire safety and relative hazard.”  Although it is typically the Architect’s responsibility to determine the Occupancy Classification, it should be remembered that the ultimately the Building Official will make the final call.  However if the code official makes a determination that you do not agree with there are means for appealing the decision. 

What if my building has mixed use?

Buildings, such as a mall (with restaurants, shops, and maybe even a hotel) that have more than one occupancy group intended are called mixed occupancy buildings.  Section 508 of the IBC has guidelines on Mixed Use Buildings and establishes guidelines for allowable height, area of the building, and separation.

Can you change a building’s Occupancy Classification?

Yes, you can change a building’s Occupancy Classification and you should do so if the buildings use is changing.  Your architect or engineer will need to submit to the city, county or other jurisdiction and request the change.  Typically this includes the design professional creating new stamped and sealed drawings and will typically require a permit from the building department.  The drawings should at a minimum, include a building code analysis sheet, site plan, floor plans of each level, stair details, and cross sections to illustrate wall types, insulation, ceiling heights and the relationship to the outside grade and interior floor elevations.

You should keep a few things in mind when changing an occupancy.  The change may trigger some code-required upgrades such as accessibility improvements, seismic upgrades, and some life safety improvements such as fire sprinklers and/ or rated wall partitions.  In addition, you find that the code requires more parking for your new occupancy and you simply may not have the space required to add the additional parking.