ADU Rules: Lancaster vs Topanga
How do adu rules rules compare between Lancaster, CA and Topanga, CA?
Lancaster and Topanga have similar restriction levels.
Lancaster, CA
Los Angeles County
California law (Gov. Code §65852.2) requires cities to allow ADUs on residential lots. Lancaster must comply with state standards for size, setbacks, and parking.
View full Lancaster 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 | Lancaster | Topanga |
|---|---|---|
| Max Size | 800 sq ft detached | - |
| Setbacks | 4 ft rear/side | - |
| Parking | None near transit | - |
| State Law | Gov. Code §65852.2 | - |
| 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.
Lancaster FAQ
Can I build an ADU?
Yes. California law requires all cities to allow ADUs on residential lots. Lancaster must process permits within 60 days.
Do I need to live on the property?
No owner-occupancy requirement for ADUs under current California law.
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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