California's ADU Revolution
No state in the nation has done more to expand ADU rights than California. Since 2017, the California Legislature has passed a sustained series of bills that systematically dismantled local restrictions that for decades prevented homeowners from building secondary units on their lots. The result is a legal framework that makes California uniquely permissive — cities cannot ban ADUs, cannot require owner-occupancy, cannot impose setbacks greater than 4 feet, and cannot charge impact fees for ADUs under 750 square feet. The foundation of this framework is California Government Code Section 65852.2, which has been amended multiple times and now covers accessory dwelling units (ADUs) and Junior ADUs (JADUs) comprehensively. AB 68 (2019) was a turning point: it eliminated owner-occupancy requirements statewide, reduced setbacks to a maximum of 4 feet, eliminated minimum lot size requirements, and mandated that cities process ADU applications ministerially within 60 days. AB 881 (2019) followed by prohibiting cities from requiring ADU setbacks exceeding 4 feet rear and side, eliminating impact fees for ADUs under 750 square feet, and expanding parking waivers. SB 13 (2019) further streamlined the process by prohibiting permit denials based on substandard setbacks of existing legally created structures. Together, AB 68, AB 881, and SB 13 created the modern California ADU framework. SB 9 (2022) then went further, authorizing urban lot splits on single-family parcels and allowing up to 4 units on lots previously limited to one primary dwelling plus ADUs. AB 2533 (2024) further strengthened ministerial approval standards and local compliance requirements. California's preemption of local ADU restrictions is full and enforceable — the state has established an enforcement mechanism, and cities that fail to comply can be ordered to approve ADU applications by the state Housing Accountability Act.
What You Can Build: ADU Types and Size Limits
California law recognizes three main types of accessory dwelling units, each with its own rules governing size, placement, and approval process. Understanding which type fits your lot and goals is the first step in any California ADU project. A detached ADU is a separate structure built in the backyard or on another part of your lot, entirely independent from the primary dwelling. Under California Government Code Section 65852.2(c)(2)(B), a detached ADU may be up to 1,200 square feet. It must maintain 4-foot side and rear setbacks, though no setback is required if you are converting or replacing a structure already in those setback areas. An attached ADU is an addition to the primary dwelling — a new room or unit built onto the side, rear, or above the existing structure. Attached ADUs may be up to 50 percent of the primary dwelling floor area, with a maximum of 1,200 square feet. A Junior ADU (JADU) is a California-specific subtype defined under Government Code Section 65852.22. JADUs must be created within the existing walls of a single-family residence or accessory structure (such as a garage). They are limited to 500 square feet. A JADU does not require a separate bathroom — it may share a bathroom with the primary dwelling — and does not require its own separate utility connections. The JADU shares utility connections with the primary dwelling. JADUs offer the lowest-cost path to an additional unit because no new structure needs to be built. An interior space — an oversized bedroom, a finished garage bay, an attic conversion — can become a JADU at significantly lower cost than a detached ADU. On a single-family lot, California law allows one full ADU (attached or detached) plus one JADU simultaneously, giving most single-family homeowners the ability to add two secondary units to their property. Garage conversion ADUs — converting an existing garage into a living space — are limited to the existing footprint plus 150 square feet for entrance ingress/egress. Garage conversions are among the most cost-effective ADU types because no foundation or framing work is needed for the shell.
City-by-City Breakdown: LA, SF, San Diego, San Jose, and Sacramento
While California state law sets a floor of permissiveness, individual cities have different fee schedules, permit timelines, and practical processes. Here is a comparison of the five major California cities with full ADU data on PropertyZoned. Los Angeles processes ADU permits through LADBS (Los Angeles Department of Building and Safety). Total permit fees typically range from $2,000 to $8,000 depending on project size and valuation. Detached ADUs up to 1,200 square feet are allowed. LA's LADBS ADU Express service targets 2-4 weeks for plan check, significantly faster than the standard 60-day window. Impact fees are waived for ADUs under 750 square feet per state law. San Francisco uses the SF Department of Building Inspection (SF DBI) for ADU permits. Total permit fees typically run $3,000 to $10,000 — higher than LA due to SF's higher property valuations and fee schedule. SF is entirely transit-rich, meaning parking waivers apply throughout the city. SF Planning maintains an ADU eligibility checker at sfplanning.org. SF had some of the most restrictive ADU rules before state preemption took effect, but must now process applications ministerially within 60 days. San Diego's Development Services Department (DSD) processes ADU permits with total fees typically $2,500 to $9,000. San Diego offers a Standard ADU Plan Program with pre-approved plans that reduce review time to 3-6 weeks. The coastal zone — covering Pacific Beach, La Jolla, Ocean Beach, and other coastal neighborhoods — requires a Coastal Development Permit in addition to the local building permit. San Jose processes ADU permits through PBCE (Planning, Building and Code Enforcement). Total permit fees typically run $2,500 to $8,500. San Jose is the tech capital of Silicon Valley — ADU demand is extremely high due to housing costs exceeding $1.5 million median home values. The city actively promotes ADU construction and maintains ADU resources at its city website. Sacramento generally has the lowest fees of the five major California cities. Total permit fees typically run $2,000 to $7,500. The Community Development Department (CDD) processes ADU permits in approximately 3-5 weeks. Sacramento sits along major light rail lines, and properties within half a mile of RT light rail stations qualify for parking waivers. Sacramento has adopted a particularly progressive ADU ordinance that maximizes the benefits of state law for homeowners.
JADU Rules: California's Unique Junior ADU Option
The Junior ADU (JADU) is a housing tool unique to California, created specifically to enable low-cost conversion of existing interior spaces into secondary units. Under California Government Code Section 65852.22, a JADU is defined as a unit of up to 500 square feet that is entirely within the existing walls of a single-family residence or accessory structure. The JADU rules differ from full ADU rules in important ways. A JADU does not require a separate bathroom — it may share a bathroom with the primary dwelling and is only required to have a basic efficiency kitchen (a sink, refrigerator, and cooking appliance within the JADU). The JADU does not need separate utility meters or connections to gas, water, or sewer — it shares the primary dwelling's connections. A JADU requires owner-occupancy as a condition of approval — the property owner must reside in either the primary dwelling or the JADU as their principal residence. This is an exception to California's general elimination of owner-occupancy requirements for full ADUs; JADUs retain the owner-occupancy requirement. In all five major California cities, JADUs may be up to 500 square feet and must be within the existing structure. This makes them best suited for converting large bedrooms, finished garages, or attached accessory structures. A garage conversion JADU can often be completed for $30,000 to $80,000, compared to $150,000 to $400,000 for a new detached ADU in a California city. On a single-family lot, California law allows one full ADU (attached or detached) plus one JADU. If you have a two-car garage, you might convert one bay to a JADU and build a detached ADU in the backyard — effectively adding two rental units to a single-family lot. JADUs offer a path to rental income with relatively minimal construction, making them particularly attractive in California's high-cost housing markets.
Permit Process and Costs
The ADU permit process in California follows a ministerial approval pathway — meaning the city cannot exercise discretion or impose subjective design standards. If your ADU project meets the objective standards (size limits, setbacks, height limits), the city must approve it. California Government Code Section 65852.2(a)(3) requires cities to approve or deny ADU/JADU applications within 60 days. An incomplete application pauses the clock. Most major California cities process standard ADU applications in 3-6 weeks for plan check, well within the 60-day window. The cost breakdown for a California ADU permit includes several line items. Plan check fees cover the review of architectural plans by the building department's plan checkers. These typically run $500 to $3,500 depending on the city and project size. Building permit fees cover the permit issuance and inspection services. These typically run $1,200 to $6,000. Impact fees — park, transportation, and other development impact fees — are waived by state law for ADUs under 750 square feet. For ADUs over 750 square feet, impact fees may apply, but California law (AB 881) caps them at the fees charged for a primary dwelling scaled proportionally by unit size. School developer fees are also waived for ADUs under 750 square feet per Government Code Section 65852.2(f)(3). ADUs over 750 square feet are subject to school fees at the current residential rate (approximately $4.08/sqft in many California school districts). The total permit fee range — not including school fees — is approximately $2,000 to $10,000 across California's major cities. Construction costs are the largest expense. In Los Angeles, a garage conversion ADU typically runs $50,000 to $150,000. A new detached ADU in San Francisco can reach $300,000 to $500,000. Prefabricated or modular ADU units have grown popular across California as a way to reduce construction costs and timelines; some manufacturers offer complete units installed for $100,000 to $200,000.
Recent Changes: The Legislative Timeline
California's ADU law has evolved substantially since 2017. Understanding the timeline of changes helps homeowners know exactly what protections apply to their project. AB 68 (2019) — this bill was the major turning point. It eliminated owner-occupancy requirements effective January 1, 2020, reduced setbacks to 4 feet maximum, eliminated minimum lot size requirements, and established the 60-day ministerial approval requirement. AB 881 (2019) — prohibited cities from requiring setbacks exceeding 4 feet rear and side, eliminated impact fees for ADUs under 750 square feet, and expanded parking waivers to apply whenever a garage is converted to an ADU. SB 13 (2019) — eliminated the ability of cities to deny ADU permits based on a claim that the existing structure is illegal, addressing a common tactic cities used to deny applications. SB 9 (2021) — authorized urban lot splits on single-family parcels. A homeowner may split a qualifying single-family lot into two parcels and build 2 units on each, effectively allowing up to 4 units on a previously single-family lot. The original lot must be at least 2,400 square feet, and each resulting parcel must be at least 1,200 square feet. AB 1033 (2023) — authorized local jurisdictions to optionally allow ADUs to be sold separately as condominiums from the primary dwelling unit, a significant expansion that gives homeowners more flexibility in monetizing their ADU investment. AB 2533 (2024) — further streamlined ADU permitting, clarified ministerial approval standards, and strengthened local compliance requirements, closing loopholes that some cities were using to slow-walk ADU approvals. These legislative changes have dramatically expanded homeowner rights. A homeowner who was told their property couldn't support an ADU in 2016 should look again — the rules have changed dramatically.
SB 9 Lot Split: Can You Sell Your ADU Separately?
One of the most significant expansions in California ADU law is SB 9, the Urban Lot Split bill, effective January 1, 2022. SB 9 created two related rights: the right to split a single-family lot and the right to build 2 units on a single-family lot without a lot split. For the lot split option, the original lot must be in an urbanized area or urban cluster, must be at least 2,400 square feet, and must be zoned for single-family residential use. The resulting two parcels must each be at least 1,200 square feet. Once the lot is split into two separate parcels, the owner may build up to 2 units on each parcel — for a total of 4 units on what was previously a single-family lot. Importantly, after an SB 9 lot split creates two separate legal parcels, those parcels can be sold separately. The ADU on one parcel could be sold independently of the ADU on the other parcel. This is a major shift — California law previously prohibited selling ADUs separately from primary dwellings. The lot split must be ministerially approved (no discretionary review) if it meets objective standards. SB 9 does not apply in historic districts, coastal zones, high fire hazard zones, earthquake fault zones, or floodplains. The owner applying for the lot split must intend to occupy one of the resulting units as their principal residence for 3 years after the lot split. AB 1033 (2023) built on SB 9 by allowing local jurisdictions to optionally permit ADU condominiumization — allowing ADUs to be separately sold without requiring a lot split, in jurisdictions that adopt this option. As of 2026, several California cities have explored this option. Check with your local planning department to see if your city has adopted an ADU condominium ordinance under AB 1033.
Getting Started: Your Action Plan
Starting an ADU project in California begins with research and feasibility assessment, not contractor calls. Here is the sequence that experienced California ADU builders recommend. Step 1: Check your zoning and lot. Look up your property on your city's zoning map to confirm your zone. In California, virtually all residential zones (single-family and multifamily) are eligible for ADUs under state preemption law. Note your lot size, existing structures, and setback conditions. Step 2: Decide on ADU type. Garage conversions and JADUs are the fastest and least expensive options. Detached ADUs offer the most square footage and rental value but require the most construction. Attached ADUs (room additions) fall in between. Step 3: Use PropertyZoned's ADU Feasibility Checker. Enter your city, lot size, and zone to get a preliminary assessment of what you can build based on your city's current rules. The tool draws on the same city data as the city pages. Step 4: Check your city page on PropertyZoned. Your city's ADU page covers the specific permit fees, timelines, and requirements. California has 5 major cities with full ADU data pages — use them to understand the total cost of permits before you hire an architect. Step 5: Hire an architect familiar with your city's ADU standards. California ADU permits require stamped architectural plans. Some cities (San Jose, San Diego) offer pre-approved standard plan sets that can reduce design costs and review time significantly. Step 6: Submit for permit and manage the process. California cities must respond within 60 days. Track your application status online using the city's permit portal. Most major California cities have online portals. California's ADU market has produced a robust ecosystem of ADU-specialized architects, builders, and prefab manufacturers. Research firms that specialize in your city and ADU type — they will know the local planning department's preferences and can help avoid revision cycles.
Frequently Asked Questions
Does California state law override my city's ADU rules?
Yes. California Government Code Section 65852.2 fully preempts local ADU restrictions. Your city cannot ban ADUs, cannot require owner-occupancy for full ADUs, cannot impose setbacks greater than 4 feet, and cannot charge impact fees for ADUs under 750 sqft. If your city denies an ADU application that meets state standards, you can appeal under the Housing Accountability Act.
Can I build an ADU and a JADU on the same lot?
Yes. California law allows one full ADU (attached or detached) plus one JADU on a single-family lot. The JADU must be within the existing structure (up to 500 sqft). The full ADU can be detached (up to 1,200 sqft) or attached. This means most single-family lots can have up to 3 units: the primary dwelling, one ADU, and one JADU.
How long does an ADU permit take in California?
California cities must process complete ADU/JADU permit applications within 60 days. Most major California cities process standard applications in 3-6 weeks for plan check. An incomplete application pauses the clock. Pre-approved standard plans (available in San Diego and some other cities) can reduce review time to 1-3 weeks.
Are impact fees waived for California ADUs?
Yes, for ADUs under 750 sqft. AB 881 (2019) eliminated impact fees (transportation, parks, etc.) for ADUs under 750 square feet. School developer fees are also waived for ADUs under 750 sqft per Government Code Section 65852.2(f)(3). For ADUs 750 sqft or larger, impact fees may apply but are capped proportionally compared to a new primary dwelling.