I would also like to suggest a storage method that was used at a provincial archives. The maps were left rolled and stored in ABS pipe, a stable polymer and comes in different diameters from 1/2″ to 6″. We cut the pipe to the same length, lined it with a/f 10pt. card,and stacked it laying down inside existing shelving units. It worked well, protected the rolled maps, and used existing shelving units.