An accessory dwelling unit (ADU) — a backyard cottage, a garage conversion, an attached in-law suite — is unusual in California land use: the state has stepped in over the last several years to stop local governments from zoning ADUs out of existence. So while your city or county still processes the permit, a large share of what they can and can’t require is set in Sacramento, not at city hall.
California’s ADU statutes were recodified in 2024. The rules that used to live in Government Code § 65852.2 now sit in Government Code §§ 66310–66342. The substance carried over, so older guidance that cites “§ 65852.2” is usually still describing current law — just under the old number.
What state law guarantees
The core idea of state ADU law is a floor: a city can add detail, but it cannot adopt standards that make a reasonably sized ADU impossible. The California Department of Housing and Community Development (HCD) summarizes several of those floors:
- At least 800 square feet, with 4-foot setbacks. A local agency cannot impose standards that fail to allow at least an 800 sq ft ADU with four-foot side and rear yard setbacks — attached or detached.
- A 60-day decision. When there is already a home on the lot, the local agency must ministerially approve or deny a complete ADU application within 60 days.
- “Ministerial” means no discretionary hearing. A qualifying ADU is approved against objective standards — not put to a public hearing or a design-review body — and because the decision is ministerial, CEQA (the California Environmental Quality Act) does not apply to it.
- No owner-occupancy requirement. Under the recodified law, a local agency may not require the owner to live on the property as a condition of having an ADU.
ADU vs. JADU: what's the difference?
A junior ADU (JADU) is a smaller category: no more than 500 square feet, created within the walls of an existing single-family home — often a converted bedroom with its own entrance and a small kitchen. A JADU can’t be sold separately from the main house. A standard ADU can be larger and fully detached. Many lots can have both an ADU and a JADU, which is a big part of why the law matters for homeowners thinking about rental income or multigenerational living.
The 2024 recodification also opened a door some homeowners have wanted for years: a local agency may now adopt an ordinance allowing an ADU to be sold separately as a condominium from the primary home (Gov. Code § 66342). That’s a local option, not a statewide right — so whether it’s available depends on your city or county.
Where local rules still matter
State law sets the floor; your jurisdiction fills in the rest — objective design standards, how impact and connection fees are calculated, building-code and fire requirements, and how your specific zone, lot size, and hazards (flood, fire, historic) interact with the state minimums. Two neighboring cities can both comply with state law and still hand you different answers. That gap — “the state says X, but what does my parcel and my code actually allow?” — is exactly the question a grounded, parcel-aware assistant is built to answer.