Short Answer
California state law now sets a floor for what cities must allow when it comes to ADUs. The main bills are AB 68 and companion laws (effective 2020), SB 9 (effective 2022), and SB 1211 (effective 2025). Together, these bills removed owner-occupancy rules, capped impact fees, standardized setbacks, and required ministerial permit approvals. Local governments can still regulate design and height within state limits, but they cannot effectively prohibit ADUs.
Why California Overhauled Its ADU Laws
Before 2020, local governments had wide latitude to restrict ADUs through ordinances that set minimum lot sizes, required off-street parking, imposed large impact fees, required owner-occupancy, and limited ADU sizes to the point that many projects were not economically viable. The practical result was that ADU construction remained low despite high demand for housing throughout the state.
The state legislature responded by passing a package of bills that preempted many local restrictions. The goal was not to eliminate local control entirely, but to prevent cities and counties from using local rules to block ADU production. State law now sets minimum standards that every city and county must meet, regardless of their own preferences.
The 2020 Reforms: AB 68, AB 881, and SB 13
Three bills took effect on January 1, 2020, and together they changed the baseline rules for ADU development across California.
AB 68: Size Standards, Owner-Occupancy, and Permit Timelines
AB 68 (Ting) established statewide ADU size standards that cities must honor. Local governments must allow homeowners to build:
At least an 850 sq ft ADU for a studio or one-bedroom unit
At least a 1,000 sq ft ADU for a unit with two or more bedrooms
An ADU at least 16 feet in height, in most circumstances
AB 68 also prohibited local agencies from requiring owner-occupancy as a condition of building an ADU, and reduced the permit approval timeline from 120 days to 60 days for applications on lots with an existing dwelling.
Owner-occupancy update: AB 68 initially prohibited owner-occupancy requirements through January 1, 2025. AB 976, effective January 1, 2024, made the prohibition permanent. California cities and counties cannot require you to live on the property as a condition of building or renting an ADU.
AB 881: Setbacks and Parking
AB 881 addressed two areas where local restrictions had been especially common: setbacks and parking replacement.
On setbacks: no setback is required for an existing structure being converted into an ADU. For new detached ADUs, cities may require no more than four feet from the rear and side lot lines.
On parking: when a garage or covered parking structure is demolished to build or make way for an ADU, the city cannot require the lost parking spaces to be replaced. Prior to AB 881, many homeowners faced the cost of building a new carport or adding driveway spaces before their ADU could be permitted.
SB 13: Impact Fee Limits
SB 13 (Wieckowski) restricted the impact fees cities could charge on ADU construction. Under SB 13:
ADUs under 750 square feet are completely exempt from impact fees
ADUs of 750 square feet or larger must be charged proportional fees, based on the ratio of ADU size to the primary dwelling's square footage
The exemption applies to impact fees under the Mitigation Fee Act
Note: Utility connection fees and capacity charges are not impact fees under this law. Water and sewer connection charges can still be assessed separately, regardless of ADU size. Budget for these costs in addition to permit fees. For typical San Diego cost ranges, see the ADU cost guide.
SB 9 (Effective January 1, 2022): Duplexes and Lot Splits
SB 9 (Atkins) is not an ADU-specific bill, but it significantly changed what is possible on a single-family zoned lot. The law requires cities to allow two things through ministerial approval (meaning no discretionary review, public hearings, or appeal process):
Duplexes on single-family lots: A property owner can apply to build two residential units on a lot that is zoned for a single family, without needing a conditional use permit or a variance.
Urban lot splits: A single-family parcel can be divided into two lots, each of which can then have its own housing. The resulting parcels must each be at least 40% of the original lot's size.
Each lot created through a SB 9 split can also include one ADU and one Junior ADU (JADU), which means a single original parcel could theoretically support up to four or more units total. In practice, lot size, setback requirements, and utility capacity limit most projects well below that ceiling.
Important limitation: The SB 9 lot split provision includes an affidavit requirement. An applicant must intend to occupy one of the resulting units as their primary residence for at least three years from the date of approval. This is the one owner-occupancy requirement that California law does permit, and it applies specifically to SB 9 lot splits.
SB 1211 (Effective January 1, 2025): Expanding ADUs on Multifamily Properties
SB 1211 targeted multifamily housing and made three significant changes:
More detached ADUs on multifamily lots
Prior law capped detached ADUs on multifamily properties at two units. SB 1211 raised that ceiling to the lesser of eight detached ADUs or the number of existing units on the property. A fourplex lot can now support up to four detached ADUs; an eight-unit building lot can support up to eight.
Expanded parking protections
SB 1211 extended existing parking protections to uncovered parking spaces. Prior protections required only that garages and carports not need replacement when converted. Now, uncovered parking spaces that are demolished or converted for ADU construction also cannot require replacement.
Fire sprinkler protection
ADU construction cannot trigger a fire sprinkler requirement unless fire sprinklers are already required in the primary dwelling. Cities cannot use the ADU permit as an opportunity to require sprinklers in an existing home that would not otherwise need them.
What Local Governments Can Still Control
State law sets a floor, not a ceiling. Cities and counties retain authority over several areas within state-imposed limits:
Design and architectural standards: Cities can require that ADUs be compatible with the primary dwelling in materials or color, within reasonable limits. Standards cannot effectively prohibit ADUs or make them infeasible.
Height limits: Local ordinances may set maximum heights, though state law sets minimums that cities must allow (generally 16 feet, with taller allowances near transit and for certain conversions).
Short-term rental restrictions: Cities can prohibit ADUs from being used as short-term rentals (Airbnb, VRBO, etc.). State ADU law does not override local short-term rental ordinances.
Utility fees: Connection fees and capacity charges for water and sewer are not impact fees under SB 13. These can still be charged at the city's standard rates.
Nonconforming conditions: In most cases, cities cannot require a homeowner to correct existing nonconforming conditions (such as a garage that does not meet current setbacks) as a condition of ADU approval. SB 1211 clarified this.
Requirements vary by property.Coastal properties, historic districts, fire hazard zones, and HOA communities may face additional requirements beyond standard city rules. Confirm your property's specific designations with your local planning or building department before budgeting for a project.
What This Means for San Diego Homeowners
The City of San Diego has updated its Municipal Code and permit process to align with state law. San Diego homeowners benefit from the same statewide protections: no owner-occupancy requirement, standardized setbacks, capped impact fees, 60-day permit review, and no parking replacement obligation in most cases.
The City of San Diego's Development Services Department (DSD) handles ADU permit applications. Their Information Bulletin 400 is the primary local reference document for ADU requirements. For garage conversions in particular, the parking and setback rules that AB 881 and SB 1211 established apply directly to San Diego projects.
That said, San Diego properties in the Coastal Overlay Zone, within historic districts, or subject to HOA rules may face additional considerations beyond the state minimum floor.
For a full walkthrough of San Diego's specific permitting requirements, steps, and timelines, read the San Diego ADU permit guide. To understand what different ADU types cost in San Diego, see the ADU cost guide.
Homeowner Checklist: Before You Apply
Final Thoughts
California's ADU legislation has made it meaningfully easier for most homeowners to add a second unit to their property. The 2020 bills removed parking replacement burdens, established size floors cities must honor, capped impact fees, and cut permit review timelines in half. SB 9 opened up density options on single-family lots that were not previously available. SB 1211 pushed those options further for multifamily property owners.
None of this means the process is simple. Local requirements, site conditions, utility capacity, and design complexity all shape what a project actually costs and how long it takes. The best starting point is confirming your property's specific situation with your local planning department, then working with a designer or builder who knows the local permit process well.
If you are comparing ADU types for your San Diego property, the garage conversion ADU guide and the detached ADU guide for San Diego cover permit requirements and realistic costs for each project type.
Frequently Asked Questions
Can my city still ban ADUs after California's state laws?+
What did AB 68 do for California ADU owners?+
What did SB 9 change for single-family homeowners?+
Do I need to live on the property to build an ADU in California?+
What did SB 1211 change about ADUs on multifamily properties?+
Are impact fees waived for ADU construction?+
Disclaimer: This article is for informational purposes only and does not constitute legal, zoning, permitting, tax, financing, engineering, or construction advice. Requirements vary by property, city, and project type. California ADU laws change frequently. Verify current requirements with your local planning or building department and consult a licensed professional before making decisions about your ADU project.
Sources and Official Resources
- •AB 68 (Ting, 2019) — ADU owner-occupancy, size standards, and permit timelines — leginfo.legislature.ca.gov — bill_id=201920200AB68. Effective January 1, 2020.
- •AB 881 (Bloom, 2019) — ADU setbacks and parking replacement — leginfo.legislature.ca.gov — bill_id=201920200AB881. Effective January 1, 2020.
- •SB 13 (Wieckowski, 2019) — ADU impact fee waiver for units under 750 sq ft — leginfo.legislature.ca.gov — bill_id=201920200SB13. Effective January 1, 2020.
- •AB 976 (Quirk-Silva, 2023) — Permanent prohibition on ADU owner-occupancy requirements — leginfo.legislature.ca.gov — bill_id=202320240AB976. Effective January 1, 2024.
- •SB 9 (Atkins, 2021) — Ministerial approval for duplexes and urban lot splits — leginfo.legislature.ca.gov — bill_id=202120220SB9. Effective January 1, 2022.
- •SB 1211 (2024) — Multifamily ADU expansion, parking, and fire sprinkler protections — leginfo.legislature.ca.gov — bill_id=202320240SB1211. Effective January 1, 2025.
- •California Department of Housing and Community Development — ADU Handbook — hcd.ca.gov/policy-research/accessory-dwelling-units. Reviewed July 2026.
- •California Government Code §65852.2 — Primary ADU statute — leginfo.legislature.ca.gov. Reviewed July 2026.
California ADU regulations change frequently. This guide reflects legislation as of July 2026. Always verify the current version of applicable law with California Legislative Information (leginfo.legislature.ca.gov) and your local building department before relying on this information.