What the city cannot deny you under state ADU law

Each of these holds whatever a local standard says. A city may do better; it may not do worse.

A local development standard cannot preclude an ADU of at least 800 square feet with 4 foot side and rear setbacks. A maximum ADU size set below 850 square feet for a studio or one bedroom, or below 1,000 square feet above one bedroom. That is a separate protection from the one above and it is the one that answers a cap. At least 16 feet of height for a detached unit. No minimum lot size. A lot cannot be called too small for an ADU. A decision within 60 days, ministerially, with no hearing and no discretionary review. No owner-occupancy requirement for an ADU. Where parking may be required at all, no more than 1 space, and none where any one of the six exemptions applies. Which of them reaches a project turns on the ADU's type and pathway. Conversion of an existing garage, with the demolition permit issued alongside the ADU permit rather than separately. No impact fees under 750 square feet. No homeowners association prohibition, and no unreasonable restriction either.

The statutes are Government Code sections 66310 to 66342, renumbered in 2024 from what everybody still calls 65852.2, and the Department of Housing and Community Development publishes a handbook reading them. Same law under two numbers: an article citing the old one is not describing a different rule.

The Los Angeles ordinance allows an ADU of up to 1,200 square feet, attached or detached. That is the maximum on the City's own ordinance pathway rather than a cap on every ADU at the address: the state-law pathways, a conversion of existing space in particular, are governed by Government Code 66323 and follow their own size rules. Underneath it sit two separate state protections, and they answer different objections. The first is about development standards: a local development standard cannot preclude you building an ADU of at least 800 square feet with 4 foot side and rear setbacks. Reach for it when a setback, a lot coverage rule or a specific plan is being used to squeeze the unit. The second is about maximum sizes: a local agency cannot set a maximum ADU size below 850 square feet for a studio or one-bedroom unit, or below 1,000 square feet for a unit with more than one bedroom. Reach for it when the city's own cap is the problem. The 800 square feet does not answer that one, and treating it as though it did is the most common way this subject is got wrong.

That is the pattern to hold on to. On size the city's ordinance route is the more generous number and the two state protections sit underneath as backstops against two different kinds of refusal. On height, on the decision clock and on parking the city and the state are close, and it is the state rule that gives them their force. On the fire and hillside prohibition the city is writing something of its own, which is the one place where local is the operative word.

Los Angeles prohibits its own ordinance ADU on a lot that is in a Very High Fire Hazard Severity Zone and in a Hillside Area. Both, not either. A lot in a fire severity zone on flat ground is not caught by it, and neither is a hillside lot outside a fire severity zone, which is why the checker asks the two questions separately instead of asking one. The ordinance names limited enumerated exceptions, which this site does not list. And the prohibition reaches the City's ordinance ADU, not every ADU. A state-law ADU, meaning a conversion of existing space or a detached ADU of up to 800 square feet, is generally still available on a lot that meets both conditions, and needs its own consideration under the Los Angeles rules rather than being read out of the project. So a lot in both zones is a narrower answer than it looks: the ordinance route is closed except under those exceptions, and the state-law route is the one to ask LA City Planning about.

That last correction is worth stating twice, because it is the one that changes what somebody does next. A lot in both zones is not a lot where nothing can be built. The prohibition reaches the City's ordinance ADU, and the state-law route, a conversion of existing space or a detached unit of up to 800 square feet, is generally still open. Ask about it by name.

The numbers themselves, and the two additions to the height that owners most often leave unclaimed, are on the ADU size and height limits page.

Get the refusal in writing and get it to name the standard. A denial of a ministerial application is not an opinion, so it has to point at something, and the something is what you then measure against the floor.

Check whether the standard being cited would take you below a line above, and reach for the right protection. A development standard that would preclude 800 square feet with four foot setbacks, a maximum size set below 850 or 1,000 square feet, a parking demand where one of the six exemptions applies, a height limit under sixteen feet, a minimum lot size of any kind: each of those is a standard meeting a protection, and the first two are different protections rather than one. Parking is the one that comes up most, because the exemptions are broad and not everybody applying the rule knows how broad.

And know what the floor does not do. It does not make an incomplete application complete, it does not answer a building code question, and it does not undo the fire and hillside prohibition on the City's ordinance route, though it is what keeps the state-law route open on such a lot. If the disagreement survives all of that, it is a question for a land use attorney, and this site is not one.