The conditions the law names
California law is violated when a rental has serious defects that make it unsafe or unhealthy and the landlord fails to repair them after notice. State law (California Civil Code Section 1941.1) lists the conditions that make a home legally unfit to live in.
Those include no working heat; no hot or cold running water; broken plumbing, gas, or sewage; faulty or unsafe wiring; a leaking roof or broken windows and doors; floors, stairs, or railings in disrepair; trash pile-up the landlord will not handle; and infestations of rodents or insects. Broken door locks and missing or dead smoke or carbon monoxide detectors can also be violations. Local building and health codes add even more requirements, and some cities have their own rules.
Not every imperfection is a legal violation — normal wear and tear does not count. But a serious, unrepaired condition that threatens your health or safety usually does. If you are unsure whether your situation qualifies, a quick conversation can help.
This is general information about California tenant rights, not legal advice. Every situation is different.