How to Take Accurate Measurements for a Sliding Glass Door

Accurate measurements are critical to getting the right sized door. This video by The Home Depot shows you how to gather all the information you’ll need to order your new sliding glass door:

1. Remove the interior moulding that surrounds the old door unit. Pry it away from the door jamb with a wide flat pry bar. You should now be able to easily see the door’s rough opening, which is the structural frame that surrounds the door unit.

Pre-hung doors come in a variety of standard sizes. It’s very importan, however, that you measure your rough opening down to the fraction of an inch. For a proper fit, you must specify a standard door size no larger than the smallest dimension of your rough opening.

2. Measure the rough opening height. To get this measurement without removing the old door, simply go outside and measure from the bottom of the threshold nose to the bottom of the head jamb. Then go inside and measure from the head jamb to the rough opening header. Add these numbers together, and that’s your rough opening height. Check the height at the center and at both sides and write down the smallest measurement.

3. Measure the width of the rough opening. Do this three times as well, across the center and across the top and bottom edges. Pick the smallest measurement and write it down.

4. Measure the jamb depth of your existing door unit.

5. Finally, you need to determine which door is the active sliding door. Looking at it from the outside, if it opens on the right, the door is right-handed. If it opens on the left, the door is left-handed.