Assembly Group Occupancy Classification – per CBC 2013

(updated 8.7.2014) This post is intended to be an overview of section 303 of the California Building Code that describes the ‘Assembly’ occupancy group.

The first thing you need to understand when it comes to the term ‘Assembly, is that it is not talking about putting parts of a machine together, or other item. It is about people getting together, and all of the various things that need to be minimally accounted for when buildings are being designed as places for people to get together.

The functions most often associated with the Assembly Occupancy include but are not limited to:

  • Civic
  • Social
  • Religious
  • Recreation
  • Food or drink consumption
  • Waiting on transportation
  • Motion picture and television sound stages
  • Approved production facilities
  • Production locations

Complexities and Exceptions

Anything more than a simple designation of a building as one occupancy group invites two different possibilities- the complexities that come into play whenever something more than the average is happening, as well as the possibility of exceptions related to a variety of uses within a number of parameters.

So, the next thing you need to understand is the importance of knowing the number of people who will be attending a given event in the given space. Because of the very real possibility of things going wrong during any event, a space that contains a large number of people completing any activity must be designed with a higher baseline standard of care than those that have fewer people. So, for building spaces used for assembly purposes that will contain fewer than 50 people, the minimal categorization of a ‘B’ or ‘Business’ use will be used. Likewise, a room that is less than 750 SF will also be categorized as a Business occupancy.

The use of ‘B’ in the above situation is an exception which recognizes that the designation of ‘B’ is sufficient for a given occupant load. Another exception is when the tentative ‘A’ designation is associated with other uses, such as ‘E’ – educational. Educational uses of spaces have an even higher requirement than ‘A’ uses, because of the potentially higher concentration of people who will be unable to help themselves (such as children) leave a space if there is an emergency. In this case, an Educational space that is used for Assembly purposes will not be recategorized as an ‘A’ occupancy group as per 303.1.3

Likewise places of worship that have religious accessory educational spaces… but is extended to fewer than 100 people in 303.1.4

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