I have a 12X20 metal building that I store my supplies for my blow mold displays and additional parts need for them.
I then built a steel building with concrete floor. It is 36' by 48' (You could have parked 5 or 6 cars in it or more) This building has racks that the molds are placed on so you can see them if need be. They are never stacked on each other. The areas in the building have their own type of molds together. (Christmas,Halloween,Easter,other) Every shelf has a written inventory. All choir, angels, Santas, Elfs, Bunny, pumpkin, ghost and so on are placed together. It has to be done like that to keep up with all of them due to the volume/number of molds (YES..there is a TON of them..LOL-LOL)