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California ADU Laws & Regulations
Everything you need to know
State ADU Law
How California Took Control of ADU Rules from Cities
California has spent nearly a decade systematically removing local barriers to ADU construction. Starting with AB 68, AB 881, and SB 13 in 2019, the state established a single framework — Government Code Section 65852.2 — that every city and county must follow. Cities can still set objective design standards (things like parking, height, and landscaping), but they cannot ban ADUs, require larger setbacks than state law allows, or impose owner-occupancy conditions on standard ADUs.
The result: ADU approval in California is ministerial, not discretionary. If your project meets the objective standards, the city must approve it — no public hearings, no case-by-case judgment calls. AmerADU designs every unit to meet these standards from day one, so your application sails through review instead of getting stuck in it.
California ADU Law: By the Numbers
Key Facts and Figures
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Detached ADUs are allowed up to 1,200 square feet on virtually any residential lot, regardless of the size of the primary home
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Setbacks are capped at 4 feet from side and rear property lines — cities cannot require more
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Cities must approve or deny a complete ADU application within 60 days under state law
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Impact fees are waived entirely for ADUs under 750 square feet
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Owner-occupancy is not required for standard ADUs — only for Junior ADUs that share a bathroom with the main home
REQUIREMENTS
What State Law Actually Sets
State law sets the maximum standards a city is allowed to impose — cities cannot go stricter, only the same or more lenient. Detached ADUs top out at 1,200 sq. ft., with a height limit of 16 feet in most cases (18 feet in some circumstances near transit or multifamily zones). Side and rear setbacks cannot exceed 4 feet, and converting an existing structure — like a garage — requires no setback at all. Minimum lot size requirements have been eliminated statewide, meaning a small lot is no longer a disqualifier. Parking is waived entirely if your property sits within half a mile of public transit, within an architecturally or historically significant district, or if you're converting an existing garage or carport.
How AmerADU Helps
Permits Handled
✔ Design every unit to meet state size, height, and setback maximums
✔ Confirm parking exemption eligibility before you submit
✔ Build applications that hold up to ministerial review the first time
✔ Track legislative changes (AB 1154, SB 543, and beyond) so your project is never built to outdated rules
✔ Push back when a local jurisdiction tries to impose a standard state law doesn't allow
AmerADU's factory-built, California-certified modular units are engineered to meet state ADU law before they ever leave the factory — not retrofitted to comply after a city flags an issue. That means fewer surprises, fewer resubmissions, and a faster path from application to Certificate of Occupancy.
State ADU law changes nearly every legislative session. Our permitting team stays current on every new bill so your project is always built to today's rules, not last year's.
CALIFORNIA ADU LAW — WHAT TO EXPECT
California law gives homeowners more ADU rights than almost any other state — no owner-occupancy requirement, capped setbacks, waived parking in most urban areas, and a hard 60-day approval window. But state law is a floor, not a ceiling: every city still layers on its own objective design standards within those limits. AmerADU designs and permits every unit to meet state requirements first, then adapts to your specific jurisdiction's local rules — so you get the full benefit of state protections without getting tripped up by city-specific details.
Frequently Asked
Common Questions About California ADU Law
No. State law prohibits cities from requiring owner-occupancy on a standard ADU. You can rent out your primary home and your ADU at the same time. The one exception is a Junior ADU (JADU) that shares a bathroom with the main house — those still carry an owner-occupancy requirement.
No. ADU approval in California is ministerial. If your application meets the objective standards your city has adopted — and those standards can't exceed what state law allows — the city must approve it without a discretionary hearing or case-by-case review.
State law allows a detached ADU up to 1,200 square feet on most residential lots, regardless of how large your primary home is. Local jurisdictions cannot impose a stricter size cap than that.
No. Local ordinances can only add objective design standards within what state law permits — they cannot be more restrictive than the state framework. If a city's ordinance conflicts with state law, the state agency that oversees housing policy can require the city to revise it, and noncompliant ordinances can be voided.