ADUs are not only for single-family homes. State law also lets owners of multifamily buildings, such as apartment buildings, add units. The rules differ from the single-family rules, and condo owners face an extra layer.
LA ADU Guide is an information site. We are not a contractor, architect, lender or law firm. Rules change, so confirm everything with your building department before you spend money. This page is general information, not legal advice.
What counts as multifamily
A multifamily property is a lot with a building containing two or more dwelling units. Section 66313 defines an ADU as a unit on the same parcel as "a single-family or multi-family dwelling." Duplexes, triplexes, apartment buildings and many condo complexes fall here.
How many ADUs the state requires cities to allow
ABAG's July 2025 summary of section 66323 lists two kinds.
| Type | How many | Rules |
|---|---|---|
| Conversion ADU | At least one, up to 25 percent of the existing units | Built in non-livable space, such as storage rooms, boiler rooms, basements, attics or garages |
| Detached ADU | Up to eight on a lot with an existing multifamily building, not more than the number of existing units | Must be detached from the main building |
| Detached ADU, new multifamily project | Up to two | On a lot with a proposed multifamily building |
| JADU | Not allowed on multifamily properties | JADUs are for single-family homes |
Source: ABAG summary, table 3. The eight-unit limit came from SB 1211, effective January 1, 2025, as noted in our California ADU rules guide.
For conversions, ABAG defines "non-livable portions" as "spaces that are not used for living, sleeping, eating, cooking, or sanitation." Examples it gives: parking, storage and open space.
Size and height for multifamily ADUs
- Detached ADUs under section 66323: up to 800 square feet, side and rear setbacks of no more than four feet.
- Height: 16 feet, with 18 feet allowed on a lot with a multistory multifamily building. Near major transit, 18 feet plus 2 feet for roof pitch.
- Conversion ADUs: no new size cap, because they use existing space.
Learn more at ADU size and height limits.
What Los Angeles was told to fix
HCD's November 2024 review found two problems relevant here. It said the City's ordinance needed to "clarify correct ADU allowances" for multifamily lots. It also said a Zoning Administrator memo limited conversions to 25 percent of "permitted units," while the state statute "makes no reference to 'permitted units' when determining the number of ADUs allowed." The City may have since updated its rules; we did not verify. Ask the city which count it uses.
Condos and townhomes
A condominium is a form of ownership. Each owner holds a unit, and the association controls common areas, including land and parking. Practical points:
- A condo owner normally cannot convert common area storage or garages alone. The HOA or a vote may be needed.
- An association may set reasonable objective design rules, but may not prohibit or unreasonably restrict ADUs (ABAG, citing Civil Code 4751). Read ADU HOA rules in California.
- Who is the "applicant" matters. Ask the city whether it needs signatures from every owner or only the association.
- We did not verify how state ADU law applies to a single-unit condo owner in a townhome complex. Ask the planning department.
Renters and tenants
Adding ADUs to an occupied building affects existing tenants through noise, loss of storage or parking, and construction access. Local tenant protection laws may apply. See the rental guides in our financing hub. We have not verified specific LA tenant rules for this page.
Checklist
- [ ] Count existing units on the lot. This sets the detached limit.
- [ ] Walk the building and list non-livable space: storage, laundry, basement, garage.
- [ ] Calculate 25 percent of existing units for conversions, rounding as the city instructs.
- [ ] Confirm detached ADU location, 4-foot setbacks and height.
- [ ] If a condo, get HOA approval requirements in writing.
- [ ] Check fire, egress and utility capacity with the building department.
- [ ] Ask whether any tenant notice or relocation rules apply.
Common questions
Can I build detached ADUs and convert space too? ABAG's table 3 lists both types together: detached ADUs "AND" conversion ADUs.
What if I have a duplex? The conversion count is 25 percent of existing units, with at least one allowed. The detached count may be up to the number of existing units, to a maximum of eight.
Can I add a JADU? No. ABAG says JADUs are not allowed on multifamily properties.
Do the local lot coverage rules apply? For state exempt multifamily ADUs, no. The summary says they "may not be subjected to" local objective standards such as lot coverage, front setbacks or design standards.
Recent changes
SB 1211 raised the detached cap to eight units, effective January 1, 2025, and the statute was renumbered into sections 66310 to 66342 on March 25, 2024 (SB 477). Compare types in ADU vs. JADU vs. garage conversion or browse the ADU types hub.