A significant change in the 2006 IRC limits window sill heights on second story windows. As more municipalities adopt the 2006 IRC, builders need be aware of these changes and the potential effect it may have on elevations of popular plans.
The 2006 International Residential Code article R.613.2 reads as follows:
In dwelling units, where the opening of an operable window is located more than 72 inches (1829 mm) above the finished grade or surface below, the lowest part of the clear opening of the window shall be a minimum of 24 inches (610 mm) above the finished floor of the room in which the window is located. Glazing between the floor and 24 inches (610 mm) shall be fixed or have openings through which a 4-inch-diameter (102 mm) sphere cannot pass.
- Windows whose openings will not allow a 4-inch-diameter (102 mm) sphere to pass through the opening when the opening is in its largest opened position.
- Openings that are provided with window guards that comply with ASTM F 2006 or F 2090.
This new section is intended to reduce the number of falls through exterior windows for small children. Windows adjacent to exterior finished grade with more than a 72-inch difference in elevation from the window opening to such finished grade must have sills to at least 24 inches above the floor of the room where the window is located or the window opening must be protected with devices similar to a guardrail that will prevent the passage of a 4-inch sphere. The new language is applicable to every window in exterior walls, regardless of the room in the dwelling where the window is located, and as such it will need additional attention with regard to the emergency egress and rescue windows required in sleeping rooms. The maximum window sill height for emergency escape and rescue openings if 44 inches above the floor, per Section R310.1, and there is no minimum sill height requirement. As a result, if the option of raising the window sills to 24 inches is used for fall prevention, the emergency egress windows will not be affected in any way. However, if the option of providing devices that prevent passage of a 4-inch sphere is used, as allowed by the exception, then such devices must be releasable or removable from the inside without the use of tools, special knowledge, or effort, as specified in Section R310.4. The new ASTM standards F2006 and F2090, referenced in the exception, are standards for guards for non-emergency escape and emergency escape windows respectively.
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