An Accessory Dwelling Unit (ADU) is a secondary housing unit on a single-family or multi-family property. It can be detached, attached, or a converted space within an existing structure.
What types of ADUs are allowed in California?
Detached ADUs: Separate structure from the main home.
Attached ADUs: Connected to the main home.
Garage/Basement Conversions: Converting existing space into an ADU.
Junior ADUs (JADUs): Smaller units (max 500 sq. ft.) within an existing home.
Zoning & Permitting
Where can I build an ADU?
Most residential properties (zoned single-family or multi-family) are allowed to have at least one ADU and one JADU.
Do I need a permit to build an ADU?
Yes, you need building permits from your local city or county planning department.
Are there any size restrictions?
Detached ADUs: Up to 1,200 sq. ft.
Attached ADUs: Up to 50% of the main home’s size (max 1,200 sq. ft.).
JADUs: Max 500 sq. ft.
How long does the permitting process take?
California law requires local agencies to approve ADU permits within 60 days if the project meets all state and local regulations.
Construction & Utilities
Do ADUs require separate utility connections?
ADUs may need separate water, sewer, and electrical connections, but some cities allow shared connections.
Can I install solar panels on an ADU?
Yes, and new ADUs over 750 sq. ft. must comply with California’s solar mandate.
Do ADUs need parking spaces?
Not always. Parking is not required if:
The ADU is within half a mile of public transit.
The ADU is built in a historic district or within an existing home.
Costs & Financing
How much does it cost to build an ADU in California?
Costs vary but generally range from $100,000 to $300,000 depending on size, materials, and location.
Are there financing options for ADUs?
Yes, including home equity loans, construction loans, cash-out refinancing, and state/local ADU grant programs.
Rental & Usage
Can I rent out my ADU?
Yes, ADUs can be long-term rentals, but some cities restrict short-term rentals (Airbnb, VRBO).
Can I sell my ADU separately from the main house?
Usually, no. However, SB 9 allows lot splits in some cases.
HOA & Local Regulations
Can my HOA prevent me from building an ADU?
No, state law prohibits HOAs from banning ADUs, but they can enforce design guidelines.
Do local city regulations override state ADU laws?
No, but cities can have additional rules as long as they do not conflict with state ADU laws.
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