The most effective approach is to add a security deadbolt, fit a protected cylinder and, if the hinges can be seen from outside, reinforce that side so the door cannot be lifted out.
Storeroom doors are usually basic: thin sheet metal or light wood, with a basic lock. They are in basements or communal corridors where nobody passes, and they are not visited often, so an attempt can go unnoticed for weeks.
What can be done:
- A surface mounted security deadbolt, with its keep firmly fixed.
- A security cylinder with an escutcheon, if the lock allows it.
- Anti-jemmy hinge bolts if the hinges face the corridor.
If the storeroom belongs to a community, it is sometimes best to talk to the property manager first. It is all in door reinforcement.