Basement bedroom egress window — IRC R310 clear-opening, sill height, and window-well minimums

What this diagram shows

A section and elevation showing what makes a basement bedroom window a legal emergency escape opening under IRC R310. In the section on the left, the window sits in the concrete foundation wall below the grade line, opening into a window well dug into the soil; the well has a corrugated retaining wall, a gravel floor, and a permanent ladder required once the well is deeper than 44 inches. Inside, the sill is no more than 44 inches above the finished bedroom floor. The elevation on the right shows the openable sash with a net clear opening of at least 5.0 square feet — the below-grade grade-floor exception, versus 5.7 square feet above grade — with a clear width of at least 20 inches and a clear height of at least 24 inches, both minimums required at the same time. A summary panel lists the R310 minimums: net clear opening, clear width and height, sill height, window-well size, the ladder rule, and that the window must open from inside without keys or tools.