Two-Story ADUs and ADUs Above a Garage in LA.

Many LA lots are small, so building up looks attractive. The common versions are a second-story unit on top of a new detached garage, or a two-story detached unit in the back yard. This guide explains what California law says about height and stories, and where Los Angeles rules have been in conflict with it.

LA ADU Guide is an information site. We do not design or build ADUs. Rules change, so confirm every number with your building department.

The state height floor

Gov. Code section 66321(b)(4) sets the minimum height a city must allow. It is a floor, not a cap. A city can allow more. The section lists:

Put another way, the transit case plus the roof pitch bonus can reach 20 feet, as HCD told the City of Los Angeles in 2024. Transit is measured by walking distance, so check the actual route from your lot, not a straight line.

Is two stories allowed?

Yes, as long as the unit fits the height. The statute includes a sentence that matters here: the height clause "shall not require a local agency to allow an accessory dwelling unit to exceed two stories." HCD read that sentence in its November 2024 letter to Los Angeles. It said local agencies "must permit ADUs with two stories and no other deficiencies."

So two stories is the practical state floor. Three stories is not required by state law, though a city may choose to allow it.

Fitting two floors inside 16 feet is tight. A typical residential floor and roof structure uses a lot of that height. Many two-story ADUs need the 18 or 20 foot allowances, an attached design that can go to 25 feet, or a local rule that is more generous. Ask your designer to draw the section view early and measure it the way the city measures it.

ADUs above a garage

A unit above a garage is a common design. HCD's letter says local agencies "may not prevent ADUs from being constructed above detached garages or accessory structures if they meet height requirements" in section 66321(b)(4). HCD told the City of Los Angeles to remove language that conflicted with this.

There are two different projects here, and they are treated differently:

• New garage with a unit above. This is new construction. The detached height and setback rules apply, including the four-foot side and rear setback cap in section 66323(a). Parking for the main home may be a separate issue.
• Existing garage with a unit built on top. This is not the same as a conversion. A conversion uses existing space. Adding a floor on top is a new addition and often needs a structural review of the walls and footing. The existing structure may need to be strengthened. See ADU vs. JADU vs. garage conversion.

What Los Angeles said in 2024

HCD's review of the City of Los Angeles ordinance (No. 186481) found two relevant conflicts:

• The ordinance said "Structures containing a detached ADU shall not be greater than two stories." HCD said the city "must remove this language."
• The ordinance capped some detached ADUs at 16 feet and did not reflect the 18 foot transit rule or the two-foot roof pitch bonus. HCD said the city "must amend the Ordinance."

We could not confirm how or when the city responded. Because state law controls where a city rule conflicts with it, ask the department which standard it is applying to your lot today, and ask it to cite the section.

Other things that limit a second story

State height rules are only one layer. Others to check:

• Fire zones. Taller buildings and hillside lots may face extra access and sprinkler questions. See ADUs in fire hazard zones.
• Hillside and overlay areas. City hillside, coastal and historic overlays can add review. We have no confirmed list, so ask the permitting agency.
• Privacy and setbacks. State law caps the side and rear setback at four feet for the new detached ADU described in section 66323(a). Neighbors may still care about windows facing their yard. Check whether your agency has objective window or design standards.
• Structure. A second floor adds loads, stairs and a longer fire escape path. Plan review will check these.
• Stairs and egress. Where the stairs go can use up a lot of the first floor. Ask your designer to draw them in.

What a second story means for cost

We do not have a sourced cost figure for a two-story ADU. Added height usually means more framing, stairs, structural engineering and exterior work, but the amount depends on the design and the market. For a method of comparing bids, see ADU cost in Los Angeles.

Checklist before you design up

• [ ] Confirm the agency that permits your lot (City of LA, County or another city).
• [ ] Measure walking distance to a major transit stop or high-quality transit corridor.
• [ ] Ask which maximum height applies: 16, 18, 20 or 25 feet, and how the agency measures it.
• [ ] Ask whether any local story limit still applies, and which code section it cites.
• [ ] Ask whether a unit above a garage is allowed on your lot, new or existing garage.
• [ ] Check fire zone, hillside and overlay status.
• [ ] Get a structural opinion before building on an existing garage.
• [ ] Get any answers in writing.

Questions to ask the permit counter

1. What is the maximum height for a detached ADU on my parcel, and how is it measured?
2. Does the city apply a two-story limit, and which section does it rely on?
3. Can I build above a detached garage, new or existing?
4. Does my lot get the transit height?
5. Do fire or hillside rules change any of this?

For the full state framework, see California ADU rules. More guides are in the ADU types hub. Permit steps are in the permit process guide. This page is general information, not legal advice.