California ADU Laws, Costs & Permit Guide (2026)
California has some of the most permissive ADU laws in the country. State law preempts most local restrictions, owner-occupancy is no longer required, and impact fees are waived for smaller units.
California ADU At a Glance
Permit Timeline
60–120 days
Average Build Cost
$150,000 – $350,000
Maximum Size
1,200 sq ft (detached); 50% of primary home (attached)
Owner-Occupancy Required
Not required (as of 2025)
Impact Fees
Waived for ADUs under 750 sq ft
Setbacks
4 ft rear and side (detached)
Recent Law Changes in California
Permanently eliminated the owner-occupancy requirement. Homeowners no longer need to live on the property to build or rent an ADU.
Increased maximum allowable ADU height to 18 feet in multifamily zones and near transit corridors, enabling additional stories.
Further streamlined ADU approvals, requiring ministerial approval (no discretionary review) and capping permit fees.
Landmark legislation that preempted local ADU restrictions statewide, eliminated parking requirements near transit, and reduced setbacks to 4 feet.
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Browse California Contractors →Frequently Asked Questions — ADUs in California
How long does it take to get an ADU permit in California?
Most California cities must approve or deny an ADU permit application within 60 days. In practice, timelines range from 60 to 120 days depending on city workload and project complexity. Los Angeles and San Francisco tend to run longer; smaller cities are often faster.
Do I need to live on the property to build an ADU in California?
No. AB 976, effective January 1, 2025, permanently eliminated California's owner-occupancy requirement. You can build and rent an ADU without living on the property.
What is the maximum size of an ADU in California?
Detached ADUs can be up to 1,200 square feet. Attached ADUs are limited to 50% of the primary dwelling's square footage, with a maximum of 1,200 sq ft. Junior ADUs (JADUs) created within the existing home are capped at 500 sq ft.
How much does it cost to build an ADU in California?
California ADU costs typically range from $150,000 to $350,000 for a detached unit, depending on size, location, and finish level. Garage conversions and junior ADUs are significantly less expensive — often $50,000 to $150,000. San Francisco and LA costs run higher than state averages.
Can I rent out my ADU in California?
Yes. You can rent an ADU in California for any term, including short-term rentals (subject to local rules). Some cities like Los Angeles restrict short-term rentals of ADUs — check your city's short-term rental ordinance.
What are California's setback requirements for ADUs?
State law requires a minimum 4-foot rear and side setback for detached ADUs. Local jurisdictions cannot impose stricter setbacks. Front setbacks follow the local standard for the primary dwelling.
Sources
- CA HCD — ADU Handbook ↗
- CA Legislative Information ↗
- Casita Coalition — Cost Data ↗
- CA Dept. of Finance — Impact Fee Data ↗
Disclaimer: The information on this page is provided for general informational purposes only and does not constitute legal, financial, or construction advice. ADU regulations change frequently — always verify current rules with your local planning department and consult a licensed professional before making decisions. ADUHomeResource.com is not liable for any errors, omissions, or outcomes resulting from use of this information.