In the San Gabriel Valley? This article doesn't apply to you. No SGV city is inside LA city limits. See the SGV ADU guide instead.
At a glance
These cases assume a City of LA lot with a house built on or before October 1, 1978.
| How the ADU is added | The new ADU | The original house |
|---|---|---|
| Detached, newly built | Generally not under the RSO | May become RSO-covered |
| Attached, newly built | Generally under the JCO, not the RSO | Under the RSO |
| Converted from living space | May be RSO-covered | May be RSO-covered |
| Converted from non-living space | Under the JCO, not the RSO | Not stated by LAHD |
The new ADU itself usually isn't the unit that comes under rent control. The older house next to it may be.
What the RSO is
The Rent Stabilization Ordinance (RSO) is the City of Los Angeles rent control law. It limits yearly rent increases and requires a legal reason to evict.
The Los Angeles Housing Department (LAHD) runs it. The guidance in this piece comes from LAHD's own pages.
The RSO generally covers rental units built on or before October 1, 1978. A lot with only one single-family house is outside it.
That's why an ADU matters. Once the lot has a second unit, an older house on it may fall under the RSO.
Was your house built after that date? Then the RSO generally doesn't reach it. The city's eviction rule for newer rentals still can, so ask LAHD.
A junior ADU (JADU) is a small unit of up to 500 square feet inside the house. LAHD treats it the same way as an ADU in the cases below.
A new detached ADU
A detached ADU stands apart from the house, like a backyard cottage. LAHD says a new one is generally not under the RSO.
The pre-1978 house is a different story. With a second unit now on the lot, LAHD says the house may become RSO-covered.
There's one exception for the ADU. It can fall under the RSO if it replaces rental units removed under the Ellis Act.
The Ellis Act is the state law that lets an owner take units off the rental market. The city's replacement rule is LAMC § 151.28.
A new attached ADU
An attached ADU shares a wall with the house. LAHD says only the original pre-1978 house is under the RSO in this case.
The attached ADU is generally not under the RSO. The exception is when it was completed within 5 years after RSO units were withdrawn under the Ellis Act.
Without that history, the ADU falls under the city's Just Cause Ordinance (JCO). The JCO limits evictions and requires the unit to be registered. It doesn't limit rent increases.
The state rent cap doesn't reach a new ADU at first either. Under AB-1482, a unit is exempt until it's 15 years old.
LAHD's ADU page also mentions relocation pay when a tenant can't afford a large rent increase. News reports say a court struck down LA's version of that rule in 2026. Ask LAHD whether it still applies.
An ADU converted from part of the house
Some ADUs are carved out of the existing house. LAHD treats these two ways, depending on what space was converted.
If the ADU came from the house's living space, LAHD says both units may be under the RSO.
If it came from space that wasn't living space, the new ADU falls under the JCO only. LAHD's page doesn't say what happens to the house in that case. Ask LAHD.
The fine print: inspections, parking, home-sharing, fees, and what it means for each side
Other rules LAHD lists for ADUs
City inspections. Once a lot has two or more units and one is rented, the Los Angeles Housing Code applies. That brings the property into the city's rental inspection program.
Removing a tenant's parking. Building an ADU sometimes takes a parking space or storage a tenant was promised. Under the RSO, the rent has to go down to match. The change needs written notice. LAHD's regulation on this is RAC Regulation 410.
Home-sharing. Short-term rentals, like home-sharing, aren't allowed in units under the RSO.
Yearly fees. Covered units pay a yearly registration fee: $38.75 per RSO unit and $31.05 per JCO unit. There's a separate inspection fee too. Fees change, and some units can get a one-year exemption, so check LAHD's billing page before you budget.
How it affects each side
For an owner, adding an ADU can change the rules for the house you already rent. Before you build, ask LAHD's RSO Determinations Unit how your lot would be treated. A determination for your parcel is more reliable than any general guide.
For a tenant in an older house where an ADU was added, your home may now be under the RSO. That would limit rent increases and require a legal reason to evict. You can ask LAHD whether your unit is covered.
If you rent the new ADU, the RSO usually doesn't cover you. The city's JCO eviction rules may. Ask LAHD which rule applies to your unit.
Who to contact
- Landlords and renters can get answers from these offices for free.
- Los Angeles Housing Department (LAHD) (both). Runs the RSO and the Just Cause Ordinance, including yearly unit registration and fees. General hotline: (866) 557-7368. Website: housing.lacity.gov.
- LAHD RSO Determinations Unit (both). Answers whether a specific unit or lot is under the RSO. Owners can ask before building an ADU. Phone: (213) 928-9097. Website: LAHD ADU page.
- Stay Housed L.A. (renters). Free information and legal help for LA County renters at risk of eviction. Phone: (888) 694-0040. Website: stayhousedla.org.
- Housing Rights Center (both). Free housing counseling and fair housing help in Los Angeles and Ventura counties. Phone: (800) 477-5977. Email: info@housingrightscenter.org. Website: housingrightscenter.org.
- In an SGV city? The LA RSO doesn't apply there. LA County's Department of Consumer and Business Affairs (DCBA) explains state and county rent rules, including the county rule for unincorporated areas (both). Phone: (800) 593-8222. Website: dcba.lacounty.gov.
Before you act: SGV Housing is not a government agency, a housing authority, or legal counsel. This article is general information, not legal advice. Laws change, and every property is different. For official rent decisions, disputes, or registration, contact the offices above. Before you act, talk to a licensed California real estate attorney, and a CPA for tax questions.
Sources & References
- Los Angeles Housing Department — Accessory Dwelling Unit page, RSO FAQ (last modified Sept. 4, 2025)
- Los Angeles Housing Department — Rent Stabilization Ordinance overview (last modified Sept. 22, 2026)
- Los Angeles Housing Department — Just Cause for Eviction Ordinance (last modified Sept. 10, 2026)
- Los Angeles Housing Department — Annual RSO, JCO and SCEP bill (last modified June 18, 2026)
- LAHD Rent Adjustment Commission Regulation 410 — reduction in housing services
- LAist — Pasadena and LA relocation payments for rent increases struck down (July 17, 2026)