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