Is my ADU under rent control in Los Angeles? The 1978 rule, explained

Is a brand-new ADU under LA rent control?

Usually not. The Los Angeles Housing Department (LAHD) says a detached ADU is generally not subject to the RSO, and a newly built attached ADU is not subject to it either, with one exception tied to the Ellis Act ²³.

The reason is the date. The RSO generally covers rental units built on or before October 1, 1978 ¹, and a backyard house you build now is decades past that line. State law backs this up: under the Costa-Hawkins Rental Housing Act, an owner may set the initial and all later rents for a unit with a certificate of occupancy issued after February 1, 1995 ¹⁹.

The exception matters only if RSO units on your lot were taken off the rental market. LAHD says an attached ADU is subject to the RSO if it was built within 5 years after RSO units were withdrawn with Ellis Act filings ³, and a detached one can be covered under the city's replacement-unit rule for the Ellis Act ². If nobody has filed Ellis Act paperwork on your property, this does not apply to you.

Can building an ADU put my pre-1978 house under rent control?

Yes, and this is the part most owners do not see coming. A lot with only one single-family house on it is outside the RSO ¹⁸. Add a second unit and that exemption is gone: LAHD says that when a detached ADU goes behind a house built on or before October 1, 1978, the house may become subject to the RSO because of the construction of a second unit on the same parcel ².

An attached ADU does the same thing to the house. When a new attached ADU is built onto a pre-1978 house, LAHD says only the original house is subject to the RSO ³. The new unit stays out; the old one comes in.

In practice that means the rules on rent increases, registration, legal reasons for eviction and relocation payments can follow the front house the day you rent it ¹. The RSO applies to units that are rented or offered for rent ¹, so if you live in the house it mostly sits in the background, and LAHD offers a one-year exemption from registration fees for units occupied by the owner or family, renewed each year ⁶. It comes to the front if you later move out and rent the house, or sell to someone who will.

A house built after October 1, 1978 does not have this problem. In most instances, a unit built after that date is not subject to the RSO ⁸. Check the year your house was built before you assume either way.

Does it matter if I convert part of my house or my garage instead?

Yes. LAHD separates conversions by what the space was before ⁴.

• Habitable living space turned into a unit. If the ADU or JADU is carved out of a bedroom or other living space of a pre-1978 house, both units may be subject to the RSO ⁴. That is the usual way a JADU is made, so read JADU vs ADU with this in mind.
• Non-habitable, non-residential space turned into a unit. If the ADU or JADU is converted from non-habitable, non-residential space of the pre-1978 house, LAHD says the new unit is subject only to the JCO and not the RSO ⁴. That scenario speaks to the new unit; it does not say what happens to the house.
• A detached garage. A garage that stands apart from the house becomes a detached ADU, which falls under the detached rule above ².

Whether your garage is legally a garage at all is a separate question; our garage conversion permit guide shows how to look up its permit history.

If my ADU is not under the RSO, what rules apply when I rent it?

The Just Cause Ordinance. The JCO covers most rental properties in the City of Los Angeles that are not under the RSO ¹¹, and LAHD says a new ADU outside the RSO is subject to it ³.

The JCO does not cap your rent, but it does regulate evictions and requires you to register the unit ³. Once a tenant has lived in the ADU for six months or the original lease has expired, whichever comes first, you need a legal reason to end the tenancy ¹², and a no-fault eviction, such as moving a family member in, requires relocation assistance ¹³. The JCO also provides Economic Displacement Relocation for tenants who cannot afford rent increases above a certain percentage ³.

Registration has a yearly fee. LAHD lists the RSO fee at $38.75 per unit per year and the JCO fee at $31.05 ⁵. If you were thinking of short-term rentals, note that home-sharing is not allowed in units subject to the RSO ⁷.

Does the state rent cap, AB 1482, apply to my ADU or my house?

Not to a new ADU for its first 15 years, but possibly to your house. The state cap does not apply to housing issued a certificate of occupancy within the previous 15 years ¹⁶, so a new backyard house is free of it until its fifteenth year.

The cap limits increases in any 12-month period to 5% plus the change in the cost of living, or 10%, whichever is lower ¹⁷. For the Los Angeles area, LAHD lists the maximum as 8.7% from August 1, 2026 to July 31, 2027, as of October 2026 ²⁰.

Here is where an ADU changes things for the front house. Single-family homes owned by individuals can be exempt from the state cap with the right written notice, but LAHD says that exemption does not apply where there is more than one dwelling unit on the same lot, such as an in-law unit ¹⁴. So a post-1978 house that is more than 15 years old and has an ADU behind it can fall under AB 1482. A house that is already under the RSO is not covered by AB 1482, because the RSO rules apply instead ¹⁵.

The state law has an end date: the rent cap section remains in effect until January 1, 2030 ¹⁸.

What changed in the RSO rules in 2025 and 2026?

The allowed yearly increase got smaller. As of October 2026, LAHD says the City Council amended the formula to 90% of the average Consumer Price Index instead of 100%, and since February 2, 2026 the yearly increase can range from 1% to 4%, down from a 3% floor and 8% ceiling under the old rules ⁹. LAHD lists the RSO increase at 3% from July 1, 2025 to June 30, 2027 ⁹.

Two add-ons also went away. The yearly RSO increase can no longer include an extra percentage for utilities ¹⁰, and since February 2, 2026 a landlord can no longer add 10% when a dependent joins the tenancy ²³. If your pre-1978 house could come under the RSO, these are the numbers to plan with, not the old 8% ceiling.

How do I check where my lot stands?

Start with ZIMAS, the city's parcel map. LAHD says to look up your address at zimas.lacity.org and open the Housing tab, which shows the RSO and JCO status for the property ²¹.

1. Look up the address on ZIMAS and note the RSO or JCO status under the Housing tab ²¹.
2. Find out when the house was built and whether it was ever more than one unit; the permit history on ZIMAS helps.
3. Decide which layout you are planning: detached, attached, a conversion of living space, or a conversion of non-living space. Each gets a different answer from LAHD ²³⁴.
4. If the answer is unclear, ask the RSO Determinations Unit at (213) 928-9097 ²².

The year the house was built and the layout of the unit decide most of this, and it is the kind of thing a lot check settles before you pay for plans.

Quick answers

Sources

1. Accessory Dwelling Unit: Rent Stabilization Ordinance, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
2. Accessory Dwelling Unit: Scenario 1, ADU detached from original structure, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
3. Accessory Dwelling Unit: Scenario 2, ADU attached to the original structure, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
4. Accessory Dwelling Unit: Scenarios 3 and 4, conversions, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
5. Accessory Dwelling Unit: RSO and JCO fees, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
6. Accessory Dwelling Unit: temporary exemptions, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
7. Accessory Dwelling Unit: home-sharing, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
8. What is covered under the RSO, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
9. Renter Protections: RSO rent increase formula, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
10. Renter Protections: utilities add-on removed, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
11. Just Cause For Eviction Ordinance (JCO): covered units, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
12. Just Cause For Eviction Ordinance (JCO): when it applies, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
13. Just Cause For Eviction Ordinance (JCO): no-fault evictions, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
14. Just Cause For Eviction Ordinance (JCO): AB 1482 and single-family homes, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
15. Just Cause For Eviction Ordinance (JCO): units already under the RSO, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
16. Civil Code section 1947.12(d)(4): new-construction exemption from the state rent cap, State of California (text via California.Public.Law). Facts checked 2026-10-10
17. Civil Code section 1947.12(a)(1): the state rent cap, State of California (text via California.Public.Law). Facts checked 2026-10-10
18. Civil Code section 1947.12(o): sunset, State of California (text via California.Public.Law). Facts checked 2026-10-10
19. Civil Code section 1954.52(a)(1) (Costa-Hawkins Rental Housing Act), State of California (text via California.Public.Law). Facts checked 2026-10-10
20. City of Los Angeles Renter Protections Notice (Rev 10/01/2026): state rent cap, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
21. City of Los Angeles Renter Protections Notice (Rev 10/01/2026): RSO and JCO lookup, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
22. Accessory Dwelling Unit: RSO Determinations Unit, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10
23. What Falls Under RSO: dependent increase removed, Los Angeles Housing Department (LAHD). Facts checked 2026-10-10

Greenlight is not a contractor, architect or engineer, and this is not legal advice. Rules change; every fact here shows the date we last checked it.