Lot Coverage Limits: Altadena vs Castaic
How do lot coverage limits rules compare between Altadena, CA and Castaic, CA?
Altadena and Castaic have similar restriction levels.
Altadena, CA
Los Angeles County
Altadena R-1 max Gross Structural Area (GSA) and lot coverage = (0.25 × net lot area) + 1,000 sq ft, never exceeding 9,000 sq ft total (Altadena CSD 22.306.070.A.4).
View full Altadena rules →Castaic, CA
Los Angeles County
Lot coverage in unincorporated LA County varies by zoning district under Title 22. Community Standards Districts may impose additional lot coverage restrictions. Residential zones typically limit coverage to maintain open space, with specific percentages set by zone classification.
View full Castaic rules →Key Facts Comparison
| Fact | Altadena | Castaic |
|---|---|---|
| Code Section | Altadena CSD 22.306.070.A.4 | - |
| GSA Formula | 0.25 × lot area + 1,000 sf | - |
| Maximum Cap | 9,000 sq ft | - |
| Excluded From GSA | Cellars + auto garages/carports | - |
| Varies By | - | Zoning district and CSD |
| Residential | - | Zone-specific percentage limits |
| ADU Exception | - | State law guarantees 800 sq ft min |
| Reference | - | Title 22, Division 6 |
Highlighted rows indicate differences between cities.
Altadena FAQ
How big a house can I build on a 10,000-sq-ft Altadena lot?
Maximum GSA = 0.25 × 10,000 + 1,000 = 3,500 sq ft (excluding garage and cellar). The absolute cap is 9,000 sq ft on any lot.
Castaic FAQ
What is the maximum lot coverage in LA County residential zones?
It varies by zone. R-1 zones typically allow 35-45% lot coverage. R-2 and R-3 zones may allow 40-60%. Check your specific zone in Title 22 or contact the Department of Regional Planning at (213) 974-6411.
Do ADUs count toward lot coverage in LA County?
No. Under California state law (Gov Code 65852.2), ADUs are exempt from lot coverage maximums, floor area ratio limits, and open space requirements.
What counts as lot coverage?
All roofed structures including the main house, garage, carport, and accessory buildings. Uncovered decks, patios, and driveways are generally excluded from coverage calculations.
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