It might not be the first thing you think about when contemplating a building, but the paths out of it—in the language of architects and contractors, the means of egress—are key features of every structure designed for occupancy, and they must be designated in commercial blueprints. Exits are central to safely evacuating a building during a fire or other emergency. They are also the subject of an entire chapter (specifically, chapter 10) of the International Building Code, or IBC—the basis of building codes in all 50 states.
The Three Parts of Egress
The IBC has specific definitions for three terms related to egress that contractors should know: exit, exit access, and exit discharge. (These terms are all defined in section 202 of the IBC.)
- Exit access: This refers to the path to an exit—the route that leads to the exit stairways and horizontal exits, which lead to separate areas protected (say by a fire door) from a room where there is a hazard.
- Exit: In the IBC, this term refers to the actual exit infrastructure of a building such as exit passages, ramps, and stairways.
- Exit discharge: The last of the three parts of the egress system is where the exit meets a public way—in other words, the point where the occupant has left the building.
How Many Exits Must a Room Have?
In section 1006.2, the IBC lays out the minimum number of exits required based on the maximum occupant load:
- One exit: Maximum capacity of 49 people.
- Two exits: Maximum capacity of 500 people.
- Three exits: Maximum capacity of 1000 people.
- Four exits: Required of any space that will have an occupancy greater than 1,000.
- Residential units: In section 1006.2.1, different transient and permanent residential living situations are described with the maximum occupancy and sprinkler requirements if there is only one means of egress. For example, provided that the hotel is equipped with an automatic sprinkler system, the maximum occupancy of a hotel room (occupancy type R1) with only one exit is 10, and the distance from any point in the room to that means of egress must be 75 feet or less.
Widths of Means of Egress
Chapter 10 of the IBC also lays out minimum widths for the doors, corridors, and stairways that make up the means of egress. In buildings with a maximum occupancy load more than 50, the minimum width for stairways is 44 inches, or 1.1 meters, per section 1011.2; for doors, the figure is 32 inches, or 0.81 meters, per 1010.1.1; and for corridors, the minimum varies depending on use, as explained in 1020.1.2. Single family homes are always exempt from this rule. There’s also an exception for spiral stairs, which are only allowed to be used as a means of egress in certain circumstances.