Is legal action needed?

There are many possible answers to your question. There may be a bailment contract between you and the building owner, or you and the employer. In a bailment situation, the bailee is required to exercise ordinary care to prevent harm to the property. For example, if you put your car in a paid parking lot, this is a bailment; however, on the ticket they give you they usually limit their liability. So this raises another question, did the building owner or the employer put up any signs or issue anything in writing to limit liability? If so, your remedy may be limited by such writing. Another question, is parking in the lot a term of your employment that is required by the employer? If so, then this is not a bailment, but a contract between you and your employer whereby the employer agrees to provide parking space to you in return for your working there. Do you pay the building owner or the employer to park there? Finally, if all these questions turn out to go against you, and I am not saying they will, check your own insurance policy to see what coverage you have.