to qualify as an egress window, a window must meet every one of the following requirements
- The minimum width of the clear opening of the window must be not less than 20"
- The minimum height of the clear opening of the window must be not less than 24"
- The clear opening of the window may not be less than
820 square inches (5.7 square feet) in a window located above ground level or in a basement
- The distance from the finished floor to the bottom of the clear opening may not exceed 44 inches
clear opening
Clear
Opening:
The "clear opening" of a window is the unobstructed opening when the window is in full open position. Many remodels assume that the window opening is also the clear opening. This is not necessarily true. Illustration 1, for example, shows a casement window in full open position. Due to the way the hinge operates, the butt of the window sash extends a few inches into the window opening. The distance that the butt extends into the opening must be subtracted to get the clear opening of the window.
This is a common problem with widows that hinge from one edge of the frame, like casement windows. Very often the sash does not completely clear the frame. Manufacturers have dealt with the problem in a variety of ways, including the use of special hinges (often called "egress hinges" or "zero clearance hinges") that do rotate the sash completely clear of the opening. Another solution, if space is available, is to simply make the window wider.
The "clear opening" of a window is the unobstructed opening when the window is in full open position. Many remodels assume that the window opening is also the clear opening. This is not necessarily true. Illustration 1, for example, shows a casement window in full open position. Due to the way the hinge operates, the butt of the window sash extends a few inches into the window opening. The distance that the butt extends into the opening must be subtracted to get the clear opening of the window.
This is a common problem with widows that hinge from one edge of the frame, like casement windows. Very often the sash does not completely clear the frame. Manufacturers have dealt with the problem in a variety of ways, including the use of special hinges (often called "egress hinges" or "zero clearance hinges") that do rotate the sash completely clear of the opening. Another solution, if space is available, is to simply make the window wider.
width, height and area
If you
multiply the minimum width and minimum height of an egress opening, the result
is not the minimum 820 square inch (5.7 square foot) opening as you might
expect. It is only 480 square inches. (See Illustration 2, Window A).
This result causes some confusion since many believe that a window with a clear opening that is the minimum width and height also ought to have the minimum required area. That's not, unfortunately, the way it works. Height and width are independent of area. To reach 820 square inches the clear opening must be made either wider or higher than the minimums |
With a
20" wide opening, the height of the opening must be at least 41"
(Illustration 2, Window B).
With a 24" minimum height, the opening width has to be 34 3/16" (Illustration 2, Window C).
As a window increases in width, it can decrease in height, and still have a large enough clear opening to qualify as an egress window. The Height and Width table shows the widths and corresponding heights required for an 820 square inch clear opening.
With a 24" minimum height, the opening width has to be 34 3/16" (Illustration 2, Window C).
As a window increases in width, it can decrease in height, and still have a large enough clear opening to qualify as an egress window. The Height and Width table shows the widths and corresponding heights required for an 820 square inch clear opening.
distant from the floor
The
bottom of the clear opening can be no more than 44" above the finished
floor. It can be lower, down to about 20" or so. But if you go too low you
will trigger another section of the building code that requires tempered glass
in windows closer than 18" to the floor. Many local communities have
changed this specification to less than 44". In our area, it's a maximum
of 42" from the finished floor.
The purpose of this requirement is obvious. In order to get out of a window, an occupant must first climb up to the window, and the code authorities have decided that 44" is the highest a person should have to climb.
If the bottom of the opening is more than 44" above the finished floor, some code authorities will permit you to build one step under the window, no more than 7 3/4" high, permanently attached to the wall, floor or both. A temporary step is not allowed.
Most windows on the first and higher floors of a house easily meet this requirement. But in basements, windows are often as high as 6' above the floor, and some serious structural modification may be required to install a qualifying egress window.
The purpose of this requirement is obvious. In order to get out of a window, an occupant must first climb up to the window, and the code authorities have decided that 44" is the highest a person should have to climb.
If the bottom of the opening is more than 44" above the finished floor, some code authorities will permit you to build one step under the window, no more than 7 3/4" high, permanently attached to the wall, floor or both. A temporary step is not allowed.
Most windows on the first and higher floors of a house easily meet this requirement. But in basements, windows are often as high as 6' above the floor, and some serious structural modification may be required to install a qualifying egress window.
Information Source: http://starcraftcustombuilders.com/windows.egress.htm#.VVVE3_mqqko