What Is an Egress Window? Requirements and Sizes

Egress Window: A window that meets minimum size requirements allowing occupants to escape from a room in an emergency or firefighters to enter, required by building codes in all sleeping rooms and below-grade habitable spaces.

Where Egress Windows Are Required

Building codes require egress windows in all sleeping rooms (bedrooms), including basement bedrooms. Any habitable room below grade — a finished basement with a bedroom, for example — requires an egress window. The requirement exists because these spaces often have limited exits; an egress window provides a secondary escape route when the primary exit (a door) is blocked.

Minimum Size Requirements

The International Residential Code (IRC), adopted in most U.S. jurisdictions, specifies these minimums: a minimum net clear opening of 5.7 square feet (5.0 sq ft for ground-floor windows), a minimum clear opening height of 24 inches, a minimum clear opening width of 20 inches, and a maximum sill height of 44 inches from the floor. These are minimums — local codes may be more restrictive.

Egress Window Wells

For basement egress windows below grade, a window well must be installed to allow opening the window and exiting. Window wells must meet minimum horizontal projection requirements: at least 9 square feet of clear area, and a minimum of 36 inches horizontal dimension. Deeper window wells (more than 44 inches deep) require permanently attached ladders or steps.

Egress Windows and Permits

Adding or enlarging a window to meet egress requirements requires a building permit in most jurisdictions. When finishing a basement to include a bedroom, egress compliance is one of the first things a building inspector will check. Failure to provide egress in a basement bedroom is a common reason basement permits are failed during inspection.

Frequently Asked Questions

The IRC requires a minimum net clear opening of 5.7 square feet (5.0 sq ft at ground floor), at least 24 inches tall, at least 20 inches wide, with a sill no higher than 44 inches from the floor. A common window that meets these requirements is a 30×36-inch opening.

Yes, if the basement contains any sleeping rooms (bedrooms). If the finished basement has no bedrooms, egress windows are not strictly required by the IRC, though they're strongly recommended for safety. Any room you intend to use as a bedroom — even if not called one on the permit application — should have egress.

Not legally, in most jurisdictions. A room labeled as a bedroom must meet egress requirements. Some homeowners add rooms without permits and call them 'bonus rooms' to avoid egress requirements — but this creates safety risks and disclosure issues at resale.