Frame the rough opening to 3 inches wider than the garage door size you have selected.
Frame out garage door.
If the door is 7 tall frame the opening 7 1 5.
If you are installing a 9 wide door the opening will be 9 3 wide.
Header the header is ideally a minimum 12 wide micro laminated beam that spans the width of the garage door opening.
The pale yellowish look of pine also gives it an extra edge and something to consider.
Woodworkers prefer it because they are lightweight effortless to cut stain and hit a nail into.
Frame the rough opening to a height that is 1 5 taller than the door that you have selected.