In Section R310.1.1 of the 2006 International Residential Code, it states:

R310.1.1 Minimum opening area. All emergency escape and rescue openings shall have a minimum net clear opening of 5.7 square feet (0.530 m2).

 Grade floor openings shall have a minimum net clear opening of 5 square feet (0.465 m2).

A lot of people associate "grade floor openings" with 1st floor windows. But as you will soon see, this is not the case.

• The code states: "Where emergency escape and rescue openings are provided they shall have a sill height of not more than 44 inches (1118 mm) above the floor."
• For slab on grade residences, the code requires generally a minimum of 6"-8" elevation difference between the finish floor and the adjacent finish grade depending on what the exterior finish material is on the exterior of the residence.

As per the 2006 International Residential Code, the definition of Grade Floor Opening is: A window or other opening located such that the sill height of the opening is not more than 44 inches (1118 mm) above or below the finished ground level adjacent to the opening.

• Therefore, if the window sill dimension is 44" to finish floor, the window sill dimension from the window sill to the finish grade will be 50"-52" which does not classify the window as a grade floor opening and the opening will have to be a minimum of 5.7 SF.
• A residence that has been built on piers or pilings probably will not let the emergency escape and rescue openings be classified as grade floor openings.

So, to sum it up for a emergency escape and rescue opening to be classified as a grade floor opening and be eligible to allow a window of 5 SF in area, the window sill must be a maximum of 44" to the outside finish grade.