For the headroom you should have about 10 to 12 of space depending on the spring system you re installing.
How to install a 9 by 7 garage door.
Standard single doors are 7 ft.
High by 16 ft.
Because the doors are so large few home centers and only some garage door stores keep many doors in stock so expect to order one instead of buying it off the shelf.
The header must be flush on the same plane with back jambs.
The position of the header and back jambs are very important.
If your opening differs from this you may have to order a specialty door.
Make sure that the size of the opening matches the size of the door.
Measure the various areas where the door will be installed.
Garage doors come in standard sizes with most basic roll up single garage doors measuring about 7 feet 2 1 m tall and 9 feet 2 7 m wide.
High by 8 or 9 ft.