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Home / Code Guides / Egress Windows

Egress Window Requirements — Size, Sill Height & Window Wells

Every sleeping room and every basement with habitable space needs an emergency escape and rescue opening — the "egress window." The four numbers that govern it: 5.7 square feet, 24 inches, 20 inches, and 44 inches.

EMERGENCY ESCAPE AND RESCUE OPENINGD21FIN. FLOORNET CLEAROPENING5.7 sf MINwindow shown larger than the minimumscontrol device24" MINclear height20" MINclear width70" MAXto devicePLAN — WHERE THE OPENING LEADSopeningYARD OR COURT36" MINclear widthPUBLIC WAYopens directly to a public way, or to a yard or court that doesMINIMUMS — IRC 2021 §R310.2Net clear opening5.7 sf MINGrade-floor opening5 sf MINClear opening height24" MINClear opening width20" MINOpening control device70" MAXNot to scale. Values are code limits.NOTES · IRC 2021 §R310.1Required in basements, habitable attics and every sleeping room (§R310.1).Must be operable from the inside without keys, tools or special knowledge (§R310.1.1).A door used as the opening must be a side-hinged or sliding door (§R310.3).Net clear dimensions are the result of normal operation (§R310.2.2). 24" MIN by 20" MIN alone does not reach 5.7 sf MIN,so the area governs (§R310.2.1).EGRESS WINDOW · IRC 2021 §R310.1 · §R310.1.1 · §R310.2.1 · §R310.2.2 · §R310.3
Emergency escape and rescue openings — IRC 2021 R310.Open full diagram →
RequirementModel Code StandardSection
Where requiredBasements, habitable attics, and every sleeping roomIRC R310.1
Minimum clear opening area5.7 sq ft (5.0 sq ft allowed for grade-floor and below-grade openings)IRC R310.2.1
Minimum clear height24 in.IRC R310.2.1
Minimum clear width20 in.IRC R310.2.1
Maximum sill height44 in. above the floorIRC R310.2.2
Window wellsMinimum 9 sq ft area with 36 in. minimum horizontal dimension; wells deeper than 44 in. need a permanently affixed ladder or stepsIRC R310.2.3, R310.2.3.1
OperationOpenable from inside without keys, tools, or special knowledge; bars/grilles allowed only with compliant releaseIRC R310.1.1, R310.4

Worth knowing

  • A 24×20 window does NOT work — 24 in. × 20 in. is only 3.3 sq ft. At the minimum height of 24 in., the width must be about 34 in. to reach 5.7 sq ft.
  • Basement bedroom conversions are the #1 place inspectors find missing egress — the opening is required per sleeping room, not per basement.
  • Replacement windows in existing openings get limited relief under R310.5/existing-building provisions, but reductions below what existed are generally not allowed.
  • Ladders in window wells may encroach up to 6 in. into the required well dimensions.

Common questions

What does the code say about where required for Egress Windows?

Basements, habitable attics, and every sleeping room. (IRC R310.1)

What does the code say about minimum clear opening area for Egress Windows?

5.7 sq ft (5.0 sq ft allowed for grade-floor and below-grade openings). (IRC R310.2.1)

What does the code say about minimum clear height for Egress Windows?

24 in.. (IRC R310.2.1)

Adopted edition by state

Base-code year from BuildSpec’s adoption records. States often amend the base code, and your city or county may differ, so confirm with your building department.

Related sections and guides

This guide is BuildSpec’s own summary, not code text. It cites the 2021 International Residential Code and the 2023 National Electrical Code as model standards. The IRC 2021 text itself is in the Code Library for signed-in members; BuildSpec publishes no NEC text, which is at nfpa.org.Neither is an adoption record: your state may be on a different edition with amendments — check your jurisdiction page or get an Address Report.
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