Step 2: Measure the height of the opening at the highest point. This is the distance between the floor and the top of the finished opening. Look for general irregularities, such as un-level floor.

Step 3: Measure the width of the areas beside the openings. Up to 5" is required on each side for installation of the vertical track. If this is a 2-door installation, center post should be a min. of 10" wide.

Step 4: Measure the area between the top of the door opening and the ceiling (or to the lowest obstruction at ceiling). 

Step 5: Measure the distance from the opening to the rear of the garage or nearest obstruction. The door's backroom requirement is the door height plus and additional 18" for manual lift doors.  If an electric opener is to be installed, the door's backroom requirement is the door height plus and additional additional 4'2".

Additional items to observe:

Verify electrical outlet for door opener use.

Note any lights or stairs in the way.

Verify all wood jambs are in good condition, header is stable.

Verify the level of the floor. Was the previous door a custom fit?

Note any pipes, ductwork, etc. above the door that might obstruct operation of the door.