Quick answer: on a typical Los Angeles single-family lot you can usually build
two units, not one — one accessory dwelling unit plus one junior ADU — and on a lot with an
existing multifamily building state law can allow up to eight detached ADUs. The widespread belief
that California allows “one ADU per lot” is simply out of date. APLA Construction (CA Lic #1136359)
builds ADUs across Los Angeles, Ventura and Orange counties.
The number is set by state law, not by your city, and it depends on two things: whether your lot has a
single-family or multifamily building on it, and whether the new unit is a
conversion of existing space or new detached construction.
The controlling section is California Government Code § 66323, which requires a local agency to
approve the following ministerially — meaning over the counter, with no public hearing and no discretionary
review — in any residential or mixed-use zone.
| Your lot has’ | What state law requires the city to allow | Authority |
| An existing or proposed single-family home | One ADU + one JADU, where the units are created within the existing or proposed space of the house or an accessory structure | § 66323(a)(1) |
| An existing or proposed single-family home | One detached, new-construction ADU with four-foot side and rear setbacks | § 66323(a)(2) |
| An existing multifamily building | At least one converted ADU, and up to 25% of the existing units, created from non-livable space | § 66323(a)(3)(B) |
| An existing multifamily building | Up to eight detached ADUs — but never more than the number of existing units on the lot | § 66323(a)(4)(A)(ii) |
| A proposed multifamily building | Up to two detached ADUs | § 66323(a)(4)(A)(iii) |
This is the point most Los Angeles homeowners get wrong. Government Code § 66323(a)(1) requires the city to
approve one accessory dwelling unit and one junior accessory dwelling unit on a lot with a
proposed or existing single-family dwelling. They are separate unit types and they stack.
That paragraph comes with conditions worth knowing before you plan around it:
Separately, § 66323(a)(2) requires the city to allow one detached, new-construction ADU with
four-foot side and rear setbacks. For that unit the local agency is permitted to impose a floor area cap of
800 square feet of livable space and a height limit under § 66321(b)(4).
In practice this is why a garage conversion plus a junior unit inside the house is such a common Los Angeles
pattern — it uses two different statutory pathways on the same lot. See our
ADU vs JADU comparison for how the two unit types
differ, and our garage conversion ADU guide
for the conversion route.
If your lot has an existing multifamily building, Government Code § 66323(a)(4)(A)(ii) requires
the city to allow up to eight detached accessory dwelling units — with one hard ceiling: the number
of ADUs may not exceed the number of existing units already on the lot. A four-unit building therefore
supports up to four detached ADUs, not eight.
A proposed multifamily building is treated differently and far more conservatively:
§ 66323(a)(4)(A)(iii) allows no more than two detached ADUs. The distinction between
existing and proposed is doing a great deal of work in this statute, and it is the first thing to
establish on any multifamily feasibility review.
Those detached units are subject to four-foot rear and side setbacks and to the height limits in
§ 66321(b)(4). There is also a protection worth knowing if you own an older building:
under § 66323(a)(4)(B), if the existing multifamily dwelling already sits closer than four feet to a side or rear
property line, the city may not require you to modify the existing building as a condition of approving
a conforming ADU.
Conversions inside the building follow a separate track. Under § 66323(a)(3), ADUs can be created from portions
of an existing multifamily structure not used as livable space — storage rooms, boiler rooms,
passageways, attics, basements and garages — provided each unit meets state building standards.
§ 66323(a)(3)(B) requires the city to allow at least one such unit, and up to 25 percent of the existing
unit count. Those conversions are counted separately from the detached units above.
Government Code § 66323(b) is short and useful: a local agency may not impose any objective development
or design standard that is not authorized by this section on a unit that meets these requirements. If a plan
checker asks for a standard that does not appear in the statute, that is a question worth raising rather than
absorbing.
Two related limits in § 66321(b) are worth having to hand during design:
For how those size rules interact with Los Angeles zoning specifically, see our
ADU size limits guide and
California ADU laws for 2026.
Counting the units you are entitled to is the easy part. The constraints that actually decide how many you can
build are usually physical rather than legal:
On a single-family lot, yes in effect — Government Code § 66323(a)(1) requires cities to ministerially approve
one ADU and one junior ADU created within the existing or proposed space of the home or an accessory
structure. Separately, § 66323(a)(2) requires approval of one detached, new-construction ADU with four-foot side and
rear setbacks. On a lot with an existing multifamily building, § 66323(a)(4)(A)(ii) allows up to eight detached ADUs,
capped at the number of existing units on the lot.
Up to eight detached ADUs on a lot with an existing multifamily dwelling, but never more than the
number of units already on the lot (§ 66323(a)(4)(A)(ii)). If the multifamily building is only proposed
rather than existing, the limit drops to two (§ 66323(a)(4)(A)(iii)). Conversions of non-livable
space inside the building are counted separately and are allowed up to 25 percent of the existing unit count
(§ 66323(a)(3)(B)).
No — they are separate unit types under the statute, which is exactly why a single-family lot can have both. A
junior ADU is created within the walls of the existing home and is governed by Article 3 of the chapter (commencing at
§ 66333), which carries its own requirements. A standard ADU can be a conversion or a detached new building.
Government Code § 66323(b) says a local agency may not impose any objective development or design standard that is
not authorized by that section on a unit meeting its requirements. Approval under § 66323 is also
ministerial, meaning it does not go to a hearing or discretionary review. Separate requirements such as
building code, fire access and utility capacity still apply in full.
Yes. These are state statutes and they bind every local agency in California, including Ventura and Orange counties
where APLA also builds. What varies locally is which department reviews the permit and how that department runs its plan
check — not the number of units you are entitled to.
APLA Construction is a licensed general contractor (CA Lic #1136359) building ADUs across Los Angeles, Ventura and
Orange counties. If you are weighing a conversion plus a junior unit, or looking at a multifamily lot, we can walk the
property and tell you what it will actually support — structurally, not just on paper. Call
(818) 818-4419 or email info@aplaconstruction.com for a free consultation.
Statutory references verified against the official text of California Government Code §§ 66321 and 66323 at
leginfo.legislature.ca.gov on 6 October 2026. This article is general information about state ADU law, not legal advice
about a specific property.