Egress Window Size – How to Measure
This page shows how to measure your house for:
- Egress Window Well size needed
- Egress Window size needed
Measuring for an Egress Well
Measure from the maximum grade level (ground level) down to the floor level of the basement.
This gives you dimension A in inches:
Dimension A: ____________ inches
Subtract 28″ from dimension A to get the minimum required height of the Egress Window Well.
Dimension A _________” – 28″ = ____________” Minimum height of the Egress Window Well
The 28″ deduction is calculated as follows:
44″ maximum height from the basement floor to the bottom of the egress window to meet egress code requirements*. Subtract 44″
The Egress Well must extend below the window about 12″ depending on the Egress Window Well model chosen. See the installation instructions to determine the exact measurement. Add 12″
The Egress Well must extend above the grade level (ground level) at least 4 inches. Consider that the grade must be sloped away from the house and well for proper drainage. A minimum of 1″ slope per foot from the house is a good rule of thumb.
(44″ window height from the finished floor* – 12″ that the well should extend below the window for drainage – 4″ that the well should extend above the grade = 28″ total deduction from measurement “A”)
The minimum width of the Egress Well is determined by the size of the Egress Window you would like to use. The inside width of the Egress Well must be wider than the Egress Window.
Measuring for an Egress Window
The width of the Egress Window must fit within the Egress Well.
There is also code requirement to consider when picking a window. The window must have:
- A minimum clear opening width must be at least 20″.
- A minimum clear opening height must be at least 24″.
- A minimum clear opening size must be at least 5.7 square feet.
There are also code requirements for both natural light and ventilation.
For natural light, the glass area, in square feet, must be at least 8% of the total floor area that the Egress Window in servicing. For example: If you had an egress window that has a glass area of 48″ x 48″ or 16 square feet, that would service an area up to 200 square feet. 16 square feet = 8% of 200 square feet. If the basement area you wish to have serviced by an egress window is larger than this 8% rule allows, you can use multiple Egress Windows to achieve the minimum 8% of glass area for natural light.
For ventilation, the window’s clear open area, in square feet, must be at least 4% of the total floor area that the Egress Window is servicing. For example: if you had an egress window that has a clear opening of 24″ x 48″ or 8 square feet. That would be able to service an area no greater than 200 square feet. 8 square feet = 4% of 200 square feet. If the basement area you wish to have serviced by an egress window is larger than this 4% rule allows, you can use multiple Egress Windows to achieve the minimum 4% of clear opening size for ventilation.