An egress window is a window that is large enough to allow entry or exit if there is an emergency. Egress window requirements are used to guarantee a minimum window size and height off the ground. This article describes the sizes of egress windows and where in your home you required to have them according to the 2009 International Residential Code.
step 1 Why Egress Windows Are Required By Code
Egress window requirements are designed to make sure that windows can open enough to climb thru when there is an emergency. Egressable windows are only required in bedrooms and basements. The heights and widths of the clear openable space are designed to allow a firefighter with a oxygen tank on to climb thru the window. With this in mind it is easy to see that having egressable windows is a life safety issue. Time and experience have caused our codes to develop to what we have today. Older homes may not have egress windows because they may have been built before the current codes were created.
The basics of the 2009 IRC (International Residential Code) egress windows requirements are as follows: (these dimensions are shown in the image above)
Note: if you multiply 24 inches by 20 inches it equals 480 inches or 3.3 sf. which is less than the required 5.7 sf. So one or both dimensions will need to be bigger, they just can't be smaller. Also, there can't be window hardware that gets in the way of the clear opening.
Basement window wells also have egress requirements. The building code dictates window well size, the need for ladders and how grates or decks above can be used. You can read all the rules at the end of this article.
When describing windows (and doors), it is proper to first say the horizontal size in feet and inches and then say the vertical size in feet and inches. So a 4'-6" wide by 5'-0" tall window is described by saying 4650, "four six five o". This is the same way to describe doorway openings.
Each of the type of window has its own special requriements. This section shows you the different types of windows and the sizes of openings required to comply with fire and building egress codes. Make sure you understand the egress capabilities of different types of windows and your specific application before ordering it. Also check with your window manufacturer to make sure that the specific window you want to use is made for egress.
Slider windows have at least two panels and slide sideways in front of each other. Because one side slides over the other, only half of the window qualifies as the egressable area. This means that the window will need to be at least 4'-0" x 4'-0" or 4040 in window terminology.
Single hung windows have at least two panels and the one of the windows slides up and down. To be egressable the bottom panel would need to be the operable panel. If both panels move it is a double hung window. Either way these windows need to be fairly large to meet egress. A typical size, not custom, that meets egress is 3050
Awning windows have one panel and open by hinging on the top of the window. Because of the hardware that holds the window open it is difficult, but not impossible, to use these windows as egress windows, especially in basements.
Casement windows have one panel and are hinged on the side and swing outward. Make sure that you purchase egressable hardware with your window, it usually does not come standard. This hardware allows the window to release from the opener so that the window can rotate out of the way of the opening. The smallest casement window is usually a 2636.
Replacing Windows To Allow Egress: When replacing windows and increasing the size it is almost always easier to make it taller than to make it wider. This is because the header of the structural header above the window would need to be widened. Making it taller usually only requires lowering the sill.
If you are purchasing windows these guidelines will get you close enough to the exact size of window for designing purposes. But for the actual rough opening size you will need to contact your window manufacturer. When speaking with the manufacturer you need to specifically ask to see the documentation that the window is egressable, especially when purchasing casement windows because some of them do not have the hinge that makes them egressable by letting them open all the way.
step 5 Basement Window Egress Requirements
Basements in dwelling units and every sleeping room below the fourth story are have at least one operable window or door approved for emergency escape or rescue that shall open directly into a public street, alley, yard or exit court.
Escape or rescue windows are required to have a minimum net clear openable area of 5.7 square feet. The minimum net clear openable height of 24 inches, width of 20 inches and a finished sill height not more than 44 inches above the floor.
step 6 The 2009 IRC excerpt (International Residential Code)
SECTION R310 EMERGENCY ESCAPE AND RESCUE OPENINGS
R310.1 Emergency escape and rescue required. Basements, habitable attics and every sleeping room shall have at least one operable emergency escape and rescue opening. Wherebasements contain one or more sleeping rooms, emergency egress and rescue openings shall be required in each sleeping room. 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. Where a door opening having a threshold below the adjacent ground elevation serves as an emergency escape and rescue opening and is provided with a bulkhead enclosure, the bulkhead enclosure shall comply with Section R310.3. The net clear opening dimensions required by this section shall be obtained by the normal operation of the emergency escape and rescue opening from the inside. Emergency escape and rescue openings with a finished sill height below the adjacent ground elevation shall be provided with a window well in accordance with Section R310.2. Emergency escape and rescue openings shall open directly into a public way, or to a yard or court that opens to a public way.
Exception: Basements used only to house mechanical equipment and not exceeding total floor area of 200 square feet (18.58 m2).
1025.2 Minimum size. Emergency escape and rescue openings shall have a minimum net clear
opening of 5.7 square feet (0.53 m squared).
Exceptions: The minimum net clear opening for emergency escape and rescue gradefloor
openings shall be 5 square feet (0.46 m squared).
1025.2.1 Minimum dimensions. The minimum net clear opening height dimension shall
be 24 inches (610 mm). The minimum net clear opening width dimension shall be 20
inches (508 mm). The net clear opening dimensions shall the result of normal operation
of the opening.
1025.3 Maximum height from floor. Emergency escape and rescue openings shall have the
bottom of the clear opening not greater than 44 inches (1118 mm) measured from the
1025.4 Operational constraints. Emergency escape and rescue openings shall be operational
from the inside of the room without the use of keys or tools. Bars, grilles, grates or
similar devices are permitted to be placed over emergency escape and rescue openings
provided the minimum net clear opening size complies with Section 1025.2 and such
devices shall be releasable or removable from the inside without the use of a key, tool or
force greater than that which is required for normal operation of the escape and rescue
opening. Where such bars, grilles, grates or similar devices are installed in existing
building, smoke alarms shall be installed in accordance with Section 907.2.10 regardless
of the valuation of the alteration.
1025.5 Window wells. An emergency escape and rescue opening with a finished sill height
below the adjacent ground level shall be provided with a window well in accordance with
Sections 1025.5.1 and 1025.5.2.
1025.5.1. Minimum size. The minimum horizontal area of the window well shall be 9
square feet (0.84 m squared), with a minimum dimension of 36 inches (914 mm). This
area of the window well shall allow the emergency escape and rescue opening to be fully
1025.5.2 Ladders or steps. Window wells with a vertical depth of more than 44 inches
(1118 mm) shall be equipped with an approved permanently affixed ladder or
steps. Ladders or rungs shall have an inside width of at least 12 inches (305
mm), shall project a least 3 inches (76 mm) from the wall and shall be spaced
not more than 18 inches (457) on center (o.c.) vertically for the full height of
the window well. The ladder or steps shall not encroach into the required
dimensions of the window well by more than 6 inches (152 mm). The ladder
or steps shall not be obstructed by the emergency escape and rescue opening.
Ladders or steps required by this section are exempt from the stairway
requirements of Section 1009.
International Building Code, 2003