IRC R311: Means of Egress

Means of egress is code language for the path you take to get out of the house in an emergency. IRC Section R311 makes sure that path is wide enough, the stairs are walkable, and there is at least one real door to the outside. These rules exist because most stair falls and trapped-occupant situations trace back to stairs that are too steep, halls that are too tight, or an exit that does not actually open. Here are the numbers a custom home has to hit.

What R311 requires

The stair geometry is the most-checked part. The maximum riser height (the vertical step) is 7.75 inches, and the minimum tread depth (the part your foot lands on) is 10 inches. Those two numbers together set a comfortable, safe slope. The stairway itself must be at least 36 inches wide above the handrail. Here is the tread-and-riser language:

The maximum riser height shall be 7 3/4 inches. The minimum tread depth shall be 10 inches.

Two more numbers complete the path. Hallways serving the egress route must be at least 36 inches wide. And every dwelling needs at least one egress door that is side-hinged and gives at least 32 inches of clear width with the door open 90 degrees, which works out to roughly a 36-inch door slab. That egress door cannot require a key or special knowledge to open from the inside.

Why the numbers are what they are

A 7.75-inch riser paired with a 10-inch tread keeps the stair shallow enough that you can descend quickly in the dark without pitching forward. The code also limits how much risers can vary within one flight (3/8 inch), because an uneven step is what trips people. The 36-inch hall and 32-inch door clearance exist so an adult, or two people helping a third, can move through without turning sideways during a fire.

For example, on a two-story custom home in Phoenix, an interior designer who wants a dramatic open stair still has to land the rise and run inside these limits, or the framing inspector rejects it and the stair gets rebuilt. The cheap fix is to design the run correctly on paper; the expensive fix is tearing out poured treads.

How it connects

R311 is the "get out" half of life safety. It pairs with IRC R314 smoke alarms , which wake you up, and the emergency escape opening rules for bedrooms in R310, which give a second way out of each sleeping room. The fire separation in IRC R302 fire-resistant construction buys the time you need to use these exits.

Edition note

The core stair geometry (7.75-inch maximum riser, 10-inch minimum tread, 36-inch width) and the 32-inch egress-door clear width are unchanged across the 2018, 2021, and 2024 IRC. Handrail and guard details get small tweaks between editions, but the headline egress numbers hold steady. Confirm which edition and amendments your city enforces on the Arizona building code editions by city page.

Source

Read the stair provisions on the official ICC site: 2021 IRC R311.7 on codes.iccsafe.org . The I-Codes are copyrighted, so only the short riser-and-tread clause is quoted here.