We had a breezeway between the house I grew up in and a detached efficiency apartment next to it. It used the existing exterior walls of the house and the apartment for the side of the breezeway and both ends were framed for screens.
When it was built, it was made with a complete header and base plate for the walls and a full, shingled roof. That made it easier when we decided to close the ends in and turn that area into an actual room.
Check your local building codes. Where I live, a breezeway was forced to become enclosed to standard building codes and resulted in a tax increase since it effectively increased the square footage of the house by adding the breezeway and barn. I cut out 3ft from the end at the barn and called it a porch, took 3 years of fighting the city but they eventually had to agree that since they were not connected, they were in the wrong.