Damage in storage areas and garages
It depends on the cause and the arrangement, but if items you stored in a garage, basement, storage room, or similar space were damaged by a problem the landlord should have prevented, you may have a claim.
Storage areas, garages, and basements are prone to water intrusion, flooding, dampness, and mold, which can ruin boxed belongings, furniture, and keepsakes. If the damage came from a landlord's failure to maintain the space — a leaking roof, poor drainage, a plumbing failure, or a known moisture problem — that neglect can make the landlord responsible.
Some leases include terms about storage use and risk, so what your agreement says can matter. Even so, a landlord generally still cannot escape responsibility for damage caused by their own negligence.
Document the damaged items, the source of the problem, and any reports you made, and keep proof of value. Photos of the conditions in the storage space help too. If belongings you stored were damaged by a condition the landlord should have addressed, a free, confidential review can help you understand whether you can recover your loss.
This is general information about California tenant rights, not legal advice. Every situation is different.