01 / Plan pathChoose the right production starting point.
Regional Planning reviews development in all areas outside a city. The County publishes pre-approved ADU plans intended to speed review, and adopted a 2026 ADU ordinance amendment covering single-family properties.
Express PlanStarting at $4,500For a qualifying jurisdiction preapproved plan adapted into the property-specific architectural production set.
Custom PlanStarting at $6,500For an original floor plan and architectural production set developed around the property and homeowner.
Size affects more than floor area.
ADUs are permitted on properties zoned for single-family or multifamily residences, and a legal dwelling must exist or be proposed concurrently. Confirm the standards under the current ordinance amendment before design.
County materials state no parking is required for an ADU located outside a Very High Fire Hazard Severity Zone. Fees require confirmation with Regional Planning.
500 SFConfirm school-fee assessment rules750 SFState impact-fee protection checkpoint1,000 SFTwo-bedroom state minimum allowance1,200 SFCommon local upper-range checkpoint
03 / Site conditionsProperty conditions can change the path.
- Very High Fire Hazard Severity Zone status and its parking and construction implications
- Zoning and any community standards district
- Hillside management area and grading
- Septic versus sewer service
- Coastal Zone status in the Santa Monica Mountains
04 / Consultant screenLikely disciplines to evaluate.
- Structural engineering
- Title 24 energy documentation
- Survey where boundaries or topography require it
- Geotechnical, civil, septic or biological review when triggered
Consultants are retained only when required by the property, design, or reviewing agency. Their proposals and coordination are separate from the architectural production fee unless stated otherwise in the agreement.
05 / Property-specific next stepTurn the guide into a preliminary project report.
Enter the address to screen jurisdiction, mapped constraints, likely agencies, drawing requirements, consultants, and the preliminary fee path.
Important: This guide is general planning information, not a zoning determination, permit approval, fee quote, or guarantee of feasibility. Current parcel records, adopted codes, agency interpretations, utility requirements, site investigation, and written agency confirmation control.