I'd suggest you compile a list of the things that should be stored to reduce production costs. Make it as extensive as makes sense -- without regard to the actual space currently available. Be very detailed.
Platforms, flats, stair units, ladders, tools (drills, circular saw, reciprocating saw, supplies for each), furniture (chairs, desks, couches, tables) supplies, paint, prop construction materials (name them), glue guns/sticks, period costumes, contemporary costumes, uniforms, hats, shoes, blouses, shirts, skirts (long, medium, short), fabric, sewing machines, foldable work tables, extension cords, ETC.
Make it run for pages and ask if they can provide you with a sea train container outdoors near your theatre space to store those items that would not be damaged by the heat and moisture of weather.
Failing that, hopefully the list will make it clear that your answer is "Sorry, but No -- I can't spare any of the space I'm currently using."
Good luck!!
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Douglas "Chip" Rome
Theatre Consultant
Educational Stages
Burke VA
http://bit.ly/EdStageshttp://bit.ly/RWTEOview------------------------------