International Building Code for the Size of an Escape Window

Dimensions

• An escape window must have an opening width of at least 20 inches, according to the IBC. The minimum height requirement is 24 inches. The window must be large enough to provide a minimum net clear opening of 5.7 square feet for secondary floors. For ground floors, the minimum net clear opening must be at least 5 square feet. The maximum sill height for an escape window is 44 inches from the ground to the sill.

Net Clear Opening

• The net clear opening does not refer to the overall size of the escape window but the amount of space available for a person to crawl through during an escape. An escape window's net clear opening must equal 5.7 square feet or 5 square feet on ground floors when the area is fully clear for passage.

Safety Devices

• The IBC permits safety devices such as bars, grills and grates on escape windows. However, all safety devices must be removable without the use of keys or tools. After you remove the safety device, the net clear opening of the escape window must remain at 5.7 square feet or 5 square feet for ground floors.

Considerations/Warnings

• An escape window that meets the minimum height and width requirement does not meet the IBC's net clear opening requirement. For example, a 20-inch wide and 24-inch high escape window has a net clear opening of only 3.3 square feet. To reach the 5.7 square-foot requirement, you would need a 20-inch wide, 42-inch high window or a 34-inch wide, 24-inch tall window. To insure IBC compliance, measure your escape window for all three minimum requirements.

Recommendations

• In homes with limited space, casement windows provide a wide escape opening despite a small footprint. Casements include hinged sashes that open wider than the window frame dimensions when fully opened. Specially-constructed escape casement windows are also available.