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To calculate the size of egress openings, follow these steps:
1. Determine the occupancy type and number of occupants in the building.
2. Consult the local building codes or regulations for requirements on egress openings.
3. Measure the width and height of the doors or windows that serve as egress openings.
4. Calculate the clear opening width and height by subtracting any obstructions, such as door frames or window sills.
5. Ensure that the calculated size of the egress openings meets or exceeds the minimum requirements set by the local building codes.
6. If necessary, install additional egress openings or modify existing ones to comply with the regulations.
Remember to always consult the local building codes and regulations for specific requirements in your area.
In the event of a fire, the ability to exit the building quickly is of utmost importance. However, if you are in the basement and the windows are too small to escape through, this could pose a problem. This is why the International Residential Code (IRC) mandates the installation of egress windows in basements and in bedrooms on the first three floors of any building. In addition to safety concerns, it is also worth noting that most homes do not have more than three stories.
The IRC sets forth specific requirements for the minimum height and width of egress openings, as well as the minimum amount of open space for both egress doors and windows. The latter requirement is crucial, as a casement window may have the correct dimensions but still not provide enough space for a person to pass through if it does not open wide enough. The code also establishes the maximum height of the window sill from the floor, as an opening is not helpful if it is too high for someone to reach.
Requirements for Windows According to the IRC Code
According to the code, egress window openings must:
- Be at least 20 inches wide
- Have a minimum height of 24 inches
- Have a total “net clear” area of 5.7 square feet
Measuring the Net Clear Area of a Window
The net clear area refers to the unobstructed space that allows for easy passage when the window is fully open. Follow these instructions to measure the net clear opening area:
- Measure the width and height of the opening (in inches) with the window fully open.
- Multiply the width and height measurements, then divide the resulting number by 144 (the number of square inches in 1 square foot) to determine the net clear opening. For example, if a window opening measures 28 x 30 inches, the area would be 840 square inches. Dividing 840 by 144 equals 5.83 square feet.
It is important to note that the measurements should only be taken of the opening itself and should not include the window sash frame or other window components. Additionally, a window opening that meets the minimum width and height requirements (e.g., 20 x 24 inches) does not qualify if it has a net clear area of only 3.33 square feet.
Additional requirements for egress windows include:
- The window must be able to open from the inside without the need for a key or tools. If there are security bars or grilles, they must also be able to open from the inside without the use of special keys, tools, or knowledge.
- The window sill cannot exceed a height of 44 inches from the floor.
- Ground-floor egress windows can be smaller, with a net clear area of only 5 square feet, as there is no need for a rescue ladder on the ground floor as required on upper floors.
Tip
When converting a room into a bedroom during a remodel, it may be necessary to install a new window that meets egress code requirements. The amount of net clear area required depends on the window style and frame material. Many window manufacturers offer calculators on their websites that allow you to input the rough opening size and select a window style and material, providing you with information on whether that window meets the necessary requirements.
Criteria for Basement Windows
When the windowsill of a basement needs to be below ground level in order to maintain a distance of 44 inches from the basement floor, a window well is necessary. A window well is a dug-out space outside the window that allows for egress. The well must enable the window to be fully opened, and it must have a floor that is at least 9 square feet in area. If the well is deeper than 44 inches, a ladder or stairway must be provided inside the well. The ladder must be at least 12 inches wide and extend at least 3 inches from the wall to which it is attached.
If a basement egress window is installed beneath a deck or porch, the top of the window well cannot be less than 36 inches from the bottom of the deck or porch floor joists. However, since this leaves very little space for crawling out of the basement, local codes may increase this minimum to as much as 60 inches.
Criteria for Egress Doors
Each dwelling unit must have at least one egress door. The door opening must meet the following requirements:
- The width of the door opening must be a minimum of 32 inches, measured from the face of the door and the stop when the door is open at a 90-degree angle.
- The height of the door opening must be at least 78 inches, measured from the threshold to the top jamb’s stop.
- The door must be easily opened from the inside, without the need for a key or specialized knowledge.
