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Egress Windows

According to the International Building Code basements and sleeping quarters below the fourth story shall have at least one exterior emergency escape and rescue opening.... This “escape and rescue opening” can be a window, skylight or patio door, but it must meet certain criteria:

  • It must have a minimum net clear opening of 5.7 sq. ft. Net clear opening refers to the actual free and clear space that exists when the window is open. It is not the rough opening size or the glass panel size or any other size, but the actual opening a person can crawl through. Code officials want the opening large enough so firefighters can comfortably crawl through the window in full protective gear with an air tank on their back. Ground-floor windows only need a net clear opening of 5 sq. ft.; they can be smaller because a rescue ladder doesn't take up part of the opening.

  • The opening height must be at least 24 in., and the opening width must be at least 20 in.

  • The bottom of the clear opening must be within 44 in. of the floor.

  • The window or other opening must be operational from the inside without keys or tools.

  • Bars, grilles and grates over windows must be operational without tools or keys and still allow the minimum clear opening.

It's important to note that the bare minimum window openeing of 24 inches by 20 inches does not meet egress requirements, since its net clear opening is only 3.33 sq. ft. A window has to be taller and/or wider than these minimums to meet the 5.7-sq.-ft.-opening requirement.

Window Well Requirements:

Basement egress windows present an added challenge. Besides the height, width and overall square-footage requirements that the window must meet, there are certain requirements for the window well surrounding the window.


Window wells must:

  • Allow the rescue window opening to be fully opened.

  • Provide 9 sq. ft. of “floor area,” with a minimum dimension of 36 in. in width and in length.

  • Contain a permanently affixed ladder or steps for climbing out if the window well depth exceeds 44 in. The ladder must be at least 12 in. wide and project no less than 3 in. from the window well. It can't be obstructed by the open window or encroach on the required window well dimensions by more than 6 in. If you build the window well from timbers or modular concrete blocks, you can create steps along one side, eliminating the need for a ladder.

Installing a basement egress window can be a challenging project. You will need to excavate a large hole, cut through and remove concrete, install the code-compliant window and build out or install a prefabricated window well, all while keeping the basement walls watertight. A well built egress window will meet all code requirements and provide an aesthetically pleasing solution to this lifesaving problem. It's a huge project—but in the case of an emergency you will be grateful to have had an egress window.

Contact Lamb Excavating today to evaluate options for adding an egress window to your home.

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