Module 5 · Lesson 1
California ADU Laws Explained in Plain English
Every major California ADU protection in one plain-English lesson: approval rights, setbacks, size, height, parking, deadlines, and what cities can no longer do.
California has passed more than a dozen ADU laws since 2017. You don't need to memorize bill numbers. You need to understand one big idea and a handful of specific protections.
The big idea: the state took cities' veto away
For decades, cities used zoning to make second units practically impossible — huge setbacks, parking mandates, hearings where neighbors could object. The state legislature decided the housing shortage outweighed local preference, and rewrote the rules. Today:
ADU approval is ministerial. If your application meets the objective standards, the city must approve it. No public hearing. No neighborhood vote. No discretion. "Ministerial" means the reviewer checks boxes; they don't weigh opinions.
State law sets floors cities can't dig under. Cities keep some control — but only above minimums the state guarantees every homeowner.
The protections, in one list
Here's what state law guarantees (each gets its own lesson in this module):
- Setbacks: no more than 4 feet on sides and rear for most new ADUs; existing structures convert in place.
- Size: at least 800 SF always; 850 SF for studio/1BR; 1,000 SF for 2+ bedrooms.
- Height: at least 16 feet detached; 18 near transit; up to 25 attached.
- Parking: capped at one space, waived entirely in common situations, and never required to replace a converted garage.
- Owner-occupancy: cities can't require you to live on the property for a standard ADU.
- HOAs: cannot prohibit ADUs; only "reasonable restrictions" allowed.
- Deadlines: cities must act on complete applications within 60 days.
- Fees: no impact fees on ADUs under 750 SF.
Who enforces this on cities?
The California Department of Housing and Community Development (HCD) reviews local ADU ordinances and can find them out of compliance — and as of 2026, non-compliant local ordinances can be voided entirely, with state standards applying directly. In other words: when a city's rules conflict with state law, state law wins, and there's a referee making sure of it.
The one honest caveat
State law is the floor, but your city fills in the details — exact size caps, design standards, front setbacks, fees above the minimums. That's why every lesson in this module ends the same way: know your rights, and check your city's ordinance. Both matter.
Want the technical version?
Key statutes (renumbered in 2024 to Gov. Code §§66310–66342): AB 68/AB 881/SB 13 (2019) created the modern framework — ministerial review, the 800 SF/16-ft/4-ft protected unit, parking limits, impact-fee exemption under 750 SF. AB 2221/AB 2011-era cleanups (2022) clarified height tiers and front-setback protections. AB 976 (2023) permanently banned owner-occupancy requirements for ADUs. AB 1033 (2023) allowed cities to opt into separate condo-style sale of ADUs. AB 2533 (2024) eased legalization of pre-2020 unpermitted units. SB 1211 (2024) expanded multifamily detached ADUs. AB 1332 (2023) required pre-approved plan programs. 2025–26 legislation (e.g., SB 543, AB 1154, AB 462) tightened review timelines, standardized interior-space measurement, narrowed JADU owner-occupancy to shared-bath units, and streamlined coastal ADU permitting. HCD enforcement: §66326.
Key takeaways
- ADU approval in California is ministerial: meet the objective standards and the city must say yes — no hearings, no neighbor votes.
- State law guarantees minimums for setbacks, size, height, and parking that cities can't undercut.
- HCD polices city ordinances, and non-compliant local rules can be voided.
- State law is the floor; your city's ordinance fills in details above it — always check both.