How To Measure Your Garage Door
Measure from the inside of the finish jamb right to left, in feet and inches if necessary.
Measure from the concrete to the bottom of the finish jamb top to bottom.
Floor to ceiling (C)
Measure from the floor to the ceiling or bottom of the rafters at the front of the garage and where the opener will go (if Installing an opener).
Measure from the ceiling or rafters to the bottom edge of the finish jamb above the garage door.
Side Room (E)
There should be at least 3½ inches made up of the finish jamb (bigger board) and two 2X4" (see drawing at top right. It should be flush on the inside of the garage (all grey areas in overall drawing) If the jambs on the right and left are not flush with the header, some 2X6" pieces may be needed.