Is Condo crawl space a common element

Since 1993, I've owned a two-story partially detached condominium with a crawl space that I acceess through a door set in the foundation walls. One of the foundation walls of the crawl space (just the sheer slab) is connected to another crawl space of another two-story condomium. I've stored all my gardening materials and other boxed furniture items that can't be stored in the attic space. I've secured the door with a lock to prevent from any trespassors or inquisitive teenagers.

I've always understood the crawl space to be part of my unit because it doesn't serve other units, and all the insulation, cross ventilation and pipes serve my unit only, and that I have a right to secure my belongings.

A few weeks ago, the condominium manager told me that I must leave the door unlocked because he wants to store all of his building supplies inside my crawl space, and that it is a common area/element and because the foundation walls are not attached to the condominium. He claims that I don't own the foundation. He also assured me that nobody will steal my belongings in the crawl space area.

I think he is wrong. I don't think the crawl space is a common element, and I have a right to secure my belongings.