Ch. 5 - Means of Egress

Delia Tacheny
INT 324 - Building Codes
Reading: The Codes Guidebook for Interiors

Keywords:

• Means of Egress
• Area of Refuge
• Exit Access
• Exit 
• Exit Discharge
• Public Way

We are now entering a deep dive into the codes, and this week we read about the first and foremost safety feature of a building - the Means of Egress. The intro to Chapter 5 summarizes the definition and importance of Means of Egress this way:

A means of egress is technically defined as a continuous and unobstructed path of travel from any point in a building to a public way. More simply stated, it is the system of building components that provide a path to safety for an occupant in the event of a fire or other emergency. A means of egress consists of vertical and horizontal elements, including doorways, corridors, passageways, stairs, ramps, and intervening rooms. The design of these components is crucial to the safety of the building occupants in normal use of a building and especially during emergencies.

This chapter is hefty and goes into detail for all the necessary codes and measurements for Means of Egress... while I will not be going as in depth, hopefully this blog gives a greater understanding to safety measurements that must be considered when designing means of Egress in a building. 

Considering how important Means of Egress are, pretty much all elements must be ADA compliant or at least offer ADA compliant alternatives. The two main strategies of exiting a building are evacuation (directly exiting the building) or "defend in place" (remaining in a designated location to await assistance). An area of refuge for example is a specific location where those that are disabled can await help in the case of an emergency. Egress can be divided into three subcategories: Exit Access, Exit, and Exit Discharge. 

• The exit access is the route that leads from the area of occupancy to the entrance of the exit. (It includes any room or space occupied by a person and any doorway, aisle, corridor, stair, or ramp traveled on the way to the exit.)
• The exit is the enclosure that is between the exit access and the exit discharge/ public way. (It can be as basic as an exterior exit door or it can include enclosed stairwells and ramps. In some special cases, it can include certain corridors or passageways.)
• The exit discharge is the area between the termination of an exit and the public way. (It can be inside a building, such as the main lobby, or outside a building, such as an egress court, courtyard, patio, small alley, or other pathway to the public way.)
• The public way is the area outside a building that is legally considered public. Examples include a street, an alley, or a sidewalk. The area must have a minimum clear width and height of not less than 10 feet (3048 mm) to be considered a public way. The intent is to be a destination where occupants would be safe from exposure to a fire in the building.
  

The three components of the Means of Egress don't necessarily have to all have the same level of code compliance and fire-rating. Within means of egress, you have to consider codes for doorways, door hardware, opening force, stairways, escalators, ramps, corridors, aisles + aisle accessways.

Given the extensive amount of considerations, I will not be stating the codes for every which aspect -- most of these will need to be looked up for each individual project anyways. However, I will state some general guidelines that are important to know. 

When it comes to exit accesses, they don't necessarily have to be fully enclosed or fire rated -- this depends on the space and occupancy, etc. Here are some common codes:

• Doors must typically have a minimum clearance of 80 by 32 inches (which is usually a 36" width door). They also usually swing outwards in the direction of egress.
• Stairs have set ceiling clearances, guardrail height, handrail height, and tread/ riser dimensions. 
• Ramps usually need to be built at a 1:12 slope ratio. 
• The typical minimum width of a corridor is 44"
• Minimum Aisle widths vary between 36" - 44" and Aisle Accessways must typically be a minimum of 12" but this varies as well based on the length of the accessway.

At the end of the exit access is an actual exit, of which there are four main types typical to an interior project: exterior exit doors, enclosed exit stairways, horizontal exits, and exit passageways. Exits typically must be enclosed within fire-rated separation:

• An exterior exit door is the most common type of exit and simply consists of a doorway. It is located in the exterior wall of the building and typically leads from the ground floor of the building to the open air of an exit discharge or a public way.
• An exit stair is the most common type of enclosed exit. It includes the stair enclosure, any doors opening into or exiting out of the stairway enclosure, and the stairs and landings inside the enclosure. 
• A horizontal exit is different from the other exits because it does not lead a person to the exterior of a building. Instead, it provides a protected path to a safe refuge area. This refuge area may be another part of the same building or an adjoining building. 
• An exit passageway is a type of horizontal route or corridor that provides the same level of protection as an exit stair. An exit passageway must be a fully enclosed, fire-rated corridor that consists of the surrounding walls, the floor, the ceiling, and the doors leading into the passageway.
• *Elevators are not usually considered proper means of egress, though some exceptions are now being made.

There are SO many other important calculations to make when designing means of Egress... the spacing and arrangement of the exits (look-up the half-diagonal rule), the travel distance, and the proper signage. I'd have to write a whole book on the topic (oh wait, there already is one... so definitely read chapter 5 to understand the entirety of the topic). Hopefully, this helped cover the basics and offered some handy guidelines to consider!

Source(s):

Kennon, Katherine E., and Sharon Koomen Harmon. “Ch.5: Means of Egress.” The Codes Guidebook for Interiors, John Wiley & Sons, Inc., Hoboken, NJ, 2022.