Adequate overhang is very critical to the life and performance of a wood stile and rail door. A proper overhang will help protect your door from the elements and extend the life of the door. In most climate conditions the following formula can be used to determine the appropriate amount of overhang: X=1/2 Y (where X is the length of the overhang required and Y is the distance from the bottom of the door to the base of the overhang.) For example, if the measurement from the bottom of the door to the base of the overhang is 8 feet, then the required overhang is 4 feet. For more severe climates, very wet or dry areas, the following formula should be used: Y=X.
[How to calculate the appropriate amount of overhang]