How high does a window sill have to be above the floor to meet fall-protection rules?

Where an operable window opening is more than 72 inches above the exterior grade, the bottom of the clear opening must be at least 24 inches above the interior floor, or approved fall-protection devices must be used (IRC R312.2.1).

In dwelling units, when an operable window opening sits more than 72 inches above the grade or surface outside, the lowest part of the clear opening must be a minimum of 24 inches above the finished floor inside (R312.2.1).

The rule targets child-fall hazards from upper-story windows. If the sill is lower than 24 inches, the code allows alternatives: an opening too small to pass a 4-inch sphere, or a window opening control device or fall-prevention device complying with ASTM F2090.

It applies only to the operable opening, so fixed glazing and windows that do not open are not affected.