Overlapping paths to recovery
You may be able to, depending on the facts, though every situation is different and no outcome is guaranteed. Tenants of unpermitted units sometimes have several possible avenues for compensation.
Depending on the circumstances, compensation might include recovery of some rent paid for an unlawful unit, relocation assistance if you were displaced through no fault of your own, a rent reduction or damages for serious habitability defects, and the return of an improperly withheld deposit. If a dangerous condition in the unit caused injury, an injury claim may also seek compensation for that harm.
What you can recover depends on how the unit was illegal, its condition, what the landlord knew and disclosed, whether you were displaced, and your local rules. Keeping records — your lease, proof of rent paid, photos of conditions, any city notices, and communications with the landlord — helps establish a claim.
Because illegal-unit compensation can involve several overlapping theories, it is worth a professional look. A free, confidential review can examine your facts and explain whether you may be entitled to compensation.
This is general information about California tenant rights, not legal advice. Every situation is different.