Flat roof carports are becoming more popular. Of course, the name is slightly misleading as even flat roof carports have an imperceptible angle to the roof to allow water run off. This type of car port can either be a stand alone carport or a carport that attaches to the side of your house.
Flat roof carport kits are easy to assemble. Most flat carports are much easier to assemble that single sloped carports or shed roof or gable roof carports. Also if you don't need to be concerned about load these can be very cheap carports. Extra load on a carport can come from snow accumulation or other weight on the roof. Stand alone carports really need only be concerned about snow accumulation. Your local carport merchant will know the average potential snow loads for your area.
As mentioned in a previous post, flat roof carports have a distinct advantage over other types of carports. In the event that you are going to attached the carport to your home you have the potential to use the roof of the carport as floor to a second story structure. This structure could be as simple as a deck or as involved as an additional second floor bedroom.
In the event, that you have a window overlooking your new carport then accomplishing a second floor addition is even easier. It would be fairly easy to renovate the existing window into a door. In the event you only desire a deck then having in inside access point is not even necessary. You can access the deck from an outside stairway.
Creating storage areas in a flat top carport is much the same as it is in any other type of carport. If the carport is attached to your house, then shelves etc can be affixed to the enclosing wall. Storage is more difficult in all types of stand alone carports. Some house attached carports have back walls and this further enhances storage opportunities.
Although, there is not one perfect type of carport, flat roof carports have the advantages of being easy to assemble and cheap. They also have the potential advantage of providing the base for a second story.