IRC R310: Emergency Escape & Rescue Openings

Every bedroom in your house needs a second way out, and Section R310 of the International Residential Code (IRC) is the rule that sets the size of that escape route. The idea is simple: if a fire blocks the bedroom door, you, a child, or a firefighter in full gear has to be able to get through a window. R310 turns "big enough" into hard numbers so nobody has to guess.

What R310 requires

Every sleeping room, every basement, and every habitable attic must have at least one operable emergency escape and rescue opening. That is usually a window. A door to the outside also counts. The opening has to meet four numbers, all measured with the window opened the normal way from the inside:

• Net clear opening of at least 5.7 square feet.
• Net clear height of at least 24 inches.
• Net clear width of at least 20 inches.
• Sill height no more than 44 inches above the finished floor.

"Net clear" means the actual hole you climb through with the sash open, not the rough frame size. Here is the core requirement:

Emergency escape and rescue openings shall have a net clear opening of not less than 5.7 square feet.

Those numbers fight each other on purpose. You cannot hit 5.7 square feet using only the 24-inch and 20-inch minimums, because 24 times 20 is just 3.3 square feet. One dimension has to grow. A grade-floor opening is allowed to drop to 5.0 square feet, but bedrooms above or below grade need the full 5.7.

What it means for an Arizona custom home

On a custom home in Scottsdale or Cave Creek, this drives window selection in every bedroom. For example, a standard single-hung window only opens half its height, so the glass has to be tall enough that the open half still clears 24 inches. Casement windows pass more easily because the whole sash swings out. Your window schedule should call out the egress units by tag so the framing rough opening is right the first time.

The 44-inch sill rule matters for design choices people love in the Valley: tall window walls, deep window seats, and beds on raised platforms. If a remodel or a tall built-in pushes the effective sill above 44 inches, that bedroom fails egress even if the window is huge. Window wells handle below-grade openings on the rare Arizona basement, and they have their own minimum size and ladder rules.

Edition note

The four core numbers (5.7 square feet, 24-inch height, 20-inch width, 44-inch sill) are the same in the 2018, 2021, and 2024 IRC. The 2021 edition reorganized the section and folded in the window-well and bar-grille details, but the dimensions a homeowner cares about did not move. Which edition your city enforces is what varies, so check the Arizona building code editions by city page before you finalize a window schedule.

How it connects

R310 is the fire-escape partner to R311 means of egress , which covers the normal way out (doors, hallways, stairs). R310 is the backup route when the normal one is blocked. Both get checked at the framing and final inspections before you get a certificate of occupancy . For the full inspection sequence, see what inspections are required when building a house in Arizona .

Source

The section text lives on the official ICC site: 2021 IRC R310.1 on codes.iccsafe.org . The ICC I-Codes are copyrighted, so only the short clause above is quoted; the rest is our explanation.