I would like to add 2 things. First, do not get one of those thick
storm doors, they are too heavy in my opinion. Get the standard
thickness ( I think 1 1/8" ?).
Next double check the rough opening between your brick molds to make
sure the door will fit. Usually the rough opening requirement is on the
storm door package.
My rough opening width was 1" too small so I had to take off both
moldings and trim them down. I could have trimmed down just one side
but the storm door would not have been centered with my entry door and
it would not have looked right.