Egress Window Requirements for Bedrooms and Basements

Under the 2024 International Residential Code (IRC), every sleeping room and every basement needs at least one emergency escape and rescue opening. A window that serves that purpose must open to at least 5.7 square feet of clear space, at least 24 inches high and 20 inches wide, with the bottom of the opening no more than 44 inches above the floor. A replacement window set into an existing opening can be exempt from those size rules, but only under specific conditions.

Which rooms need an escape opening

Every sleeping room, every basement and every habitable attic needs at least one operable escape opening under Section R319.1 of the 2024 IRC. So does a room that a sleeping loft opens onto, and in a basement with bedrooms, each bedroom needs its own.

The opening has to lead directly to a public way, or to a yard or court that opens to one. The code lists exceptions: basements used only for mechanical equipment with no more than 200 square feet of floor area, storm shelters built to the ICC 500 standard, and basement sleeping rooms in homes with an automatic sprinkler system, as long as the basement has one means of egress plus one escape opening, or two means of egress.

In the 2021 edition the same subject was Section R310. The move to R319 in 2024 is why older guides and newer code books cite different numbers for the same rule. States and cities adopt an edition and may amend it, so the edition your building department enforces is the one that counts.

The U.S. Fire Administration’s escape-planning advice rests on the same idea: find 2 ways out of every room, and make sure doors and windows are not blocked.

The four numbers, and how they are measured

The code measures the net clear opening: the open space the window gives when it is opened normally. Section R319.2.2 says the dimensions must be the result of normal operation of the opening, so they are measured with the window opened the way it is designed to open, not with a sash taken out.

Area: at least 5.7 square feet (R319.2.1).
Grade-floor exception: 5 square feet is enough for a grade-floor opening, defined in Chapter 2 as one whose clear opening bottom sits no more than 44 inches above or below the finished ground outside.
Height: at least 24 inches of clear opening.
Width: at least 20 inches of clear opening.
Sill: the bottom of the clear opening no more than 44 inches above the floor (R319.2.3).

The minimum height and width do not multiply out to the minimum area. A 24-by-20-inch opening is 480 square inches, about 3.3 square feet. At 24 inches of clear height, the opening has to be about 34.2 inches wide to reach 5.7 square feet, which is 820.8 square inches.

An escape opening under a deck, porch or cantilever must open fully and leave a path at least 36 inches high and 36 inches wide to a yard or court (R319.2.4).

Window wells for below-grade openings

A basement escape window whose opening sits below the ground outside needs an area well of at least 9 square feet, plus a ladder or steps once the well is deeper than 44 inches (R319.4). The details:

Size: at least 9 square feet of horizontal area, a projection and width of at least 36 inches each, and room for the window to open fully.
Ladder or steps: required, permanently attached, once the well is deeper than 44 inches. Ladders need an inside width of at least 12 inches, must stand at least 3 inches off the wall, and need rungs no more than 18 inches apart. Steps need at least 12 inches of width, 5-inch treads and risers of 18 inches or less.
Encroachment: the ladder or steps may intrude up to 6 inches into the required well dimensions.
Drainage: into the foundation drainage system, unless the foundation sits on well-drained soil of the types the code lists.

Bars, grilles, locks and window stops

Security bars, grilles, covers and screens may go over an escape opening or its well only if they release or come off from the inside without a key, a tool, or more force than it takes to open the window normally. The required clear opening has to remain (R319.4.4).

The window itself must open from inside without keys, tools or special knowledge (R319.1.1). Window opening control devices and fall prevention devices that meet the ASTM F2090 standard are allowed on escape windows, and the 2024 edition says they must be mounted no higher than 70 inches above the finished floor. Once such a device is released, the window still has to provide the full required opening (R321.2.2).

ENERGY STAR’s storm window guidance raises a related point for add-on units: choose a storm window that matches how the existing window operates, which it calls especially important in bedrooms.

When you replace an existing window

Replacement windows have their own exemption. Under Section R319.5, a replacement in an escape opening is exempt from the size, dimension and sill-height rules of R319.2, and from R319.4.4, when all of these hold:

Size: it is a standard size from the manufacturer that fits within the existing frame or rough opening, and no larger standard size of that window would fit.
Style: it is the same operating style as the old window, or a style that gives an equal or greater opening area.
Use: the replacement is not part of a change of occupancy.

Section R319.5.1 requires opening control devices on such replacements to be mounted within the 70-inch limit of R319.1.1, or as low as the device can be installed within the existing clear opening.

The 2024 International Existing Building Code has a parallel exemption in Section 505.3, built on the same largest-standard-size condition.

Two related rules for existing basements:

New bedrooms: a sleeping room newly created in an existing basement needs an escape opening that meets R319.1 (R319.7). Other basement alterations and repairs do not trigger one.
Change of occupancy: where it creates the need for an escape opening, R319.7.1 accepts an existing operable window with at least 4 square feet of clear opening, 22 inches high and 20 inches wide. A replacement window qualifies if it meets those numbers and the standard-size condition above.

Permits and local rules

The model IRC requires a permit before anyone constructs, enlarges, alters or repairs a building (R105.1), and its list of work exempt from permits (R105.2) does not name window replacement. Local amendments can add exemptions, so the building department’s rules decide whether a like-for-like window swap needs a permit.

Cutting a new opening in a foundation wall, or enlarging an existing one, alters the structure of the building. That is work the building department reviews before it starts.

When to hire a professional, and what to ask

Enlarging an opening or cutting a new one involves the wall’s structure, excavation for a well and drainage. That is contractor work under a permit. Even a straight replacement is worth checking against the numbers above before the window is ordered.

Questions to ask a contractor:

What will the net clear opening area, height and width be when the new window is opened normally?
How high will the bottom of the clear opening sit above the finished floor?
Does this replacement qualify for the replacement-window exemption, and is it the same operating style or one with an equal or greater opening?
Which code edition does the building department enforce here, and who pulls the permit?
For a basement opening: what are the well dimensions, is a ladder or steps needed, and where does the well drain?
For bars or window stops: how do they release from inside, and can every person in the household operate them without special knowledge?

Write the answers into the contract, with the measured opening sizes per window.