Section 1941.1 is the checklist that gives § 1941 its content. Subdivision (a) says a dwelling is deemed untenantable if it substantially lacks any of the listed affirmative standard characteristics, or is a unit described in Health and Safety Code § 17920.3 or § 17920.10. The list is concrete: effective waterproofing and weather protection of roof and exterior walls including unbroken windows and doors; plumbing and gas facilities maintained in good working order; an approved water supply capable of producing hot and cold running water; heating facilities in good working order; electrical lighting and wiring in good working order; building and grounds kept clean, sanitary and free of debris, filth, rubbish, garbage, rodents and vermin; adequate rubbish receptacles; floors, stairways and railings in good repair; a locking mail receptacle in a residential hotel; and — for leases entered into, amended or extended on or after 1 January 2026 — a working stove and a working refrigerator, the refrigerator subject to a written opt-out the tenant may choose.
The operative word is "substantially". The test is not whether every item on the list is in perfect order but whether the dwelling substantially lacks one of them, which is why a single loose railing and a staircase with no railing at all are not the same case. And the section is written as a floor: it says what makes a dwelling untenantable, not what makes it good.
Because the list is closed and specific, the argument in a real dispute is usually about which item a defect falls under rather than whether the tenant deserves the repair. A recurring leak is item (1); a bathroom fan that does not clear steam is not on the list at all, though the mould it produces may bring in the sanitation item or the separate mould provisions. Which item applies, and whether the lack is substantial, is a factual question worth taking to a lawyer or a local code enforcement office.