The area in any structure that provides space for storage(noun)
WordNet. Princeton University. 2010.
Use "storage space" in a sentence
"In a storage space under some eaves, Sister Apothecaire filled oaken cabinets with her unguents and restoratives, purgatives and negatives."
"I’ve seen her resew clothes—convert a pair of old pants into a patch-pattern skirt or rip out the lining of a jacket from the mothball darkness of the storage space above the refrigerator and turn it into a silk blouse—but I never suspected that such intricate elegance could emerge from under her hands."
"Put roll-out wire baskets in the undersink storage space if your RV doesn’t already offer this feature."