Frame the rough opening to 3 inches wider than the garage door size you have selected.
Pole barn garage door rough opening.
The height of the rough opening would be the height of the garage door plus the thickness of whatever you are putting underneath the header in addition to the thickness of the mortar etc.
99 of the residential garage doors that we run across are different than these widths.
The rough opening is equal to the size of the door but you need to figure back head and side room before choosing and installing the new garage door.
If you are installing a 9 wide door the opening will be 9 3 wide.
Next you will need to know your door height.
Frame the rough opening to a height that is 1 5 taller than the door that you have selected.
2x6 door mounting board adjusted based upon door manufacturer build make sure to leave enough turning radius for opening size and slab thickness door track radius can be between 12 and 18 depending on installation kit bracing overhead door rails in pole barn.