Everything You Need to Know About ADU Requirements in California
Introduction
California families face a severe housing shortage. As your household grows, finding a suitable home under current market conditions can feel out of reach. Fortunately, California’s lawmakers have enacted a series of new laws to make accessory dwelling units (ADUs) an accessible option. This guide breaks down the key ADU requirements across the state, highlights the latest legal updates, and explains how you can add a new living space that benefits your family.
What Are ADUs?
Accessory dwelling units are independent residential spaces on the lot of an existing single-family home. You might also hear them called granny flats, in-law suites, backyard cottages, or secondary dwelling units. ADUs must be built on foundations with full utility hookups. They can be:
Every ADU remains part of the main property but can house tenants, relatives, or guests.
How ADUs Ease California’s Housing Crunch
California’s booming economy created demand without enough new homes. Median home prices exceed $600,000, and prices in major markets have jumped by 75% over five years. Even high earners often commute long distances to find housing. Building ADUs unlocks hidden capacity on residential lots. You gain affordable, nearby space for aging parents, adult children, or rental income—and you avoid battling for scarce listings.
Statewide ADU Laws You Should Know
Recent legislation has removed obstacles, capped fees, and accelerated approvals. Below are the most impactful bills:
SB 13 (Wieckowski) — Eliminates the five‑year owner‑occupancy requirement; waives replacement parking unless over half a mile from transit; cuts permit timelines to 60 days; reduces or waives impact fees on units up to 750 sq ft (official text)
SB 1226 (Bates) — Lets unpermitted ADUs be legalized based on the building code in effect when constructed, bringing older units up to code (official text)
SB 330 (Skinner) – Housing Crisis Act of 2019 — Locks in zoning and design standards once you submit a complete preliminary application; limits permit fees and hearings; prevents downzoning or arbitrary permit caps (official text)
AB 1763 (Chiu) — Expands density bonuses when 100% of units are affordable; allows 20% middle‑income units in mixed developments; offers extra height and concessions near transit (official text)
AB 1485 (Wicks) — Clarifies SB 35’s streamlined, CEQA‑exempt approval for housing‑rich or mixed‑use projects; extends eligibility to Bay Area projects with 20% moderate‑income units; sets three‑year approval windows and defines mixed‑use standards (official text)
AB 68 (Ting) & AB 881 (Bloom) — Mandate 60‑day ministerial ADU approvals; prohibit local rules on size, lot minimums, and replacement parking; permit both an ADU and junior ADU on a single lot; relax setback requirements (AB 68 text, AB 881 PDF)
AB 670 (Friedman) — Bars HOAs from prohibiting ADUs on single‑family lots; allows HOAs to set reasonable design standards; provides a five‑year amnesty to legalize unpermitted ADUs without urgent safety issues (official text)
AB 671 (Friedman) — Requires local governments to include ADU incentives in housing plans; directs the state to publish all grants and subsidies by December 31, 2020 (official text)
AB 587 (Friedman) — Permits nonprofit‑built ADUs to be sold separately from the main home, expanding affordable homeownership options (official text)
Local Rules Matter
State law preempts many barriers, but cities and counties set zoning, setback, parking, and design guidelines that can affect unit size, utility connections, and fees. Always review your local ordinance before designing your ADU.
Next Steps to Build Your ADU
Conclusion
ADUs unlock flexible, affordable housing right in your backyard. California’s recent reforms remove outdated rules, speed approvals, and cut costs. Whether you need space for relatives or rental income, now is the time to explore ADUs.
Frequently Asked Questions
Q: Can I rent my ADU short-term?
A: Many jurisdictions require 30-day minimum leases. Confirm local rules before listing.
Q: Do ADU fees apply to garage conversions?
A: Fees may be reduced or waived for units under 750 sq ft. Garage conversions generally qualify.
Q: Are HOAs still allowed to set design standards?
A: HOAs can impose reasonable design and size guidelines but cannot ban ADUs outright.
Q: Can I sell my ADU separately?
A: Nonprofit‑built ADUs may be sold independently under AB 587.
Conclusion
Accessory dwelling units unlock affordable, flexible living space right on your property, and California’s recent ADU reforms have removed many of the old hurdles—capped fees, sped-up approvals, relaxed parking rules, and more. Whether you’re planning a backyard cottage for aging parents, a rental suite for extra income, or an in-law conversion, now is the perfect time to turn that hidden square footage into real value.
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