Meeting the proper egress requirments for your basement has become common knowloage among renovators & home owners alike. However many people are still unclear on the requirements for the window wells. Along with the installation of windows such as hopper windows, these requirements can become even more confusing.
The minimum window well size is 760mm (30in), provided the window does not open outward. As pictured in the diagram provided by Jeldwen Windows & Doors; If the window opens outward the window well needs to be 760mm (30in) larger then the distance measured from the exterior of the house to the top of the window well. These requirements ensure egress windows are not installed in locations where they would be unusable in the event of a fire.
In addition to the requirements for the window well, any covering installed on top of the well itself needs to be removable from the inside without the use of special tools. It should be noted to properly test this, you should attempt to remove the cover as if you were exiting the basement through the window. This is recommended as the increased difficulty could make a covering that is removable from above the window well, extremely difficult or impossible from below.