How to Measure Exterior Doors
- 1). Measure the width of the door in inches between the casing's inside edges. The casing is the timber lining for the door opening. You may need to remove the trim work to see it.
- 2). Add 1/2 inch to the measurement. This is your new door width.
- 3). Measure the height of the door in inches, from the top inside casing to the bottom inside casing.
- 4). Add 1/2 inch the the measurement. This is your new door height.
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