ADU Rules: Carson vs Topanga
How do adu rules rules compare between Carson, CA and Topanga, CA?
Carson has fewer restrictions than Topanga.
Carson, CA
Los Angeles County
Carson allows accessory dwelling units (ADUs) and junior ADUs (JADUs) on parcels with existing or proposed single-family or multifamily dwellings, in conformance with state ADU law (Cal. Gov. Code §65852.2 and §65852.22). The Carson Municipal Code zoning chapter (Article IX, Chapter 1) implements these standards ministerially.
View full Carson rules →Topanga, CA
Los Angeles County
Topanga is an unincorporated CDP in Los Angeles County governed by LA County Code Title 22 §22.140.640 (Accessory Dwelling Units and Junior Accessory Dwelling Units), most recently amended April 2024. Detached ADUs are capped at 1,200 sq ft; multifamily-lot ADUs have no maximum size under county rules. Topanga lies within the Santa Monica Mountains Coastal Zone, so a Coastal Development Permit also applies.
View full Topanga rules →Key Facts Comparison
| Fact | Carson | Topanga |
|---|---|---|
| Governing law | Cal. Gov. Code §65852.2 (ADUs); §65852.22 (JADUs) | - |
| Local code | Carson Municipal Code Article IX, Ch. 1 (Zoning) | - |
| By-right ADU size | 800 sq ft, 16-ft height, 4-ft setbacks | - |
| Max detached ADU | 1,200 sq ft | - |
| JADU max | 500 sq ft (within existing SFD) | - |
| Review type | Ministerial (no public hearing) | - |
| Approval timeline | 60 days from complete application (state mandate) | - |
| Governing Code | - | LA County Code §22.140.640 |
| Single-Family | - | 1 ADU + 1 JADU per lot |
| Multifamily Detached | - | Up to 2 new + conversion ADUs |
| Coastal Permit | - | Required (Santa Monica Mtns LCP) |
| Side/Rear Setback | - | 4 ft (new construction) |
Highlighted rows indicate differences between cities.
Carson FAQ
Can Carson ban ADUs in single-family zones?
No. Gov. Code §65852.2 preempts local bans. Carson must allow ADUs ministerially on any single-family or multifamily lot.
Do I need a public hearing for an ADU?
No. State law requires ministerial (over-the-counter) approval within 60 days of a complete application.
Can I build an ADU and a JADU on the same lot?
Yes. State law allows one ADU plus one JADU on a single-family lot.
Topanga FAQ
Who regulates ADUs in Topanga?
Topanga is unincorporated, so LA County Department of Regional Planning regulates ADUs under LA County Code Title 22 §22.140.640, not a separate city ordinance.
Do I need a Coastal Development Permit for a Topanga ADU?
Yes. Topanga falls within the certified Santa Monica Mountains Local Coastal Program, so most ADU construction requires a Coastal Development Permit in addition to the building permit.
Can a Topanga multifamily lot add detached ADUs?
Yes. Under LA County Code §22.140.640, multifamily lots may add up to two detached new-construction ADUs plus conversion ADUs within non-livable space (up to 25% of existing units).
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