One of the first steps in any building project is evaluation of the appropriate occupancy group. This drives building size, building height, construction type, exiting and fire separations.
One of the groups with the largest numbers of occupants is Assembly. Assembly is the occupancy for gatherings of groups of people for meeting spaces, eating establishments, performance spaces, etc. Section 303 of the International Building Code defines the 5 types of assembly occupancies.
First, the exceptions. A building or space with less than 50 occupants is a B occupancy (Business). Also, a space with less than 750 sf that is an accessory space is Group B.
A-1 is the group for viewing of performing arts. These spaces frequently have fixed seating and include movie theaters, concert halls and traditional theaters.
A-2 is the group that applies to eating establishments. It includes restaurants, bars, banquet halls and night clubs.
A-3 is the group for worship, recreation and amusement uses. It is also the catch-all for other uses not specifically called out. The uses include galleries, religious worship spaces, courtrooms, sports spaces without seating, lecture halls, libraries, museums, pool halls, bowling alleys, transportation waiting areas and funeral parlors.
A-4 is the group used for indoor sporting events that have spectator seating. That means arenas, pools, tennis courts, skating rinks, indoor soccer fields and so on.
A-5 is the group used for outdoor sporting events. This includes stadiums, bleachers and grandstands along with amusement park structures.
Of course if you’re looking at assembly occupancies there are quite a number of additional code sections that you should review. Please feel free to contact me with any questions.