California leads the nation in ADU legislation, and the laws continue evolving. The 2025-2026 legislative updates represent a shift from expanding ADU rights to enforcing compliance and faster permitting. This guide explains the key laws every California homeowner and builder should understand.
California ADU Law Timeline
| Year | Key Legislation | Impact |
|---|---|---|
| 2017 | SB 1069, AB 2299 | Removed barriers, required ministerial approval |
| 2020 | AB 68, SB 13, AB 881 | Eliminated parking, reduced fees, allowed JADUs |
| 2022 | AB 2221, SB 897 | Streamlined permitting, increased height limits |
| 2024 | SB 1211, AB 2533 | Expanded ADU rights, pre-approved plans |
| 2025 | SB 9, SB 543, AB 1332 | Enforcement, accountability, coastal streamlining |
| 2026 | Various updates | Full enforcement of 2025 laws, Coastal Commission guidance |
AB 2221: Streamlined Permitting
What It Does
AB 2221 requires all agencies involved in reviewing ADU plans — including planning departments, building departments, and utility companies — to respond within 60 days of plan submission.
Key Provisions
- 60-day response requirement: All reviewing agencies must complete their review within 60 days
- Coastal Zone streamlining: By July 1, 2026, the California Coastal Commission must provide local governments clear guidance on amending local coastal programs to simplify ADU approvals
- Utility company compliance: Electric, gas, water, and sewer utilities must respond to ADU connection requests within the 60-day window
- Reduced barriers: Cannot require specific architectural styles that significantly increase costs
Impact on Homeowners
AB 2221 means faster, more predictable timelines. Before this law, utility companies and coastal reviews could delay ADU projects by months. Now, all agencies operate under the same 60-day clock.
SB 9 (2025): Enforcement and Accountability
What It Does
SB 9 (2025 version) adds enforcement teeth to existing ADU laws by penalizing local governments that fail to comply with state requirements.
Key Provisions
- Submit or lose it: Local agencies must submit ADU ordinances to HCD within 60 days of adoption. Failure renders the ordinance "null and void"
- Deficiency response: If HCD identifies deficiencies in a local ordinance, the jurisdiction has 30 days to respond. Failure renders the ordinance void
- State standards apply: When local ordinances are voided, state default ADU standards apply — which are generally more permissive
Impact on Homeowners
SB 9 prevents local governments from adopting restrictive ADU ordinances and then ignoring state oversight. If your city's ADU rules are overly restrictive and have not been properly submitted to HCD, they may not be enforceable.
Current California ADU Rules (2026)
Size Limits
- Detached ADU: Up to 1,200 sq ft
- Attached ADU: Up to 50% of the primary dwelling's living area or 1,200 sq ft, whichever is less
- JADU (Junior ADU): Up to 500 sq ft, created within the existing primary dwelling
- Both allowed: One ADU and one JADU permitted on a single-family lot
Height Limits
- Standard detached: Up to 18 feet
- Two-story on multi-family lots: Up to 25 feet
- Within 1/2 mile of transit: Up to 18 feet for detached (some cities allow 2 stories)
Setback Requirements
- Rear and side: 4 feet minimum
- Front: Standard front setback of the zone applies
- Conversions: No setback requirements for converting existing structures
Parking
- No parking required for ADUs within 1/2 mile of public transit
- No parking required for ADUs in historic districts
- No parking required for ADUs that are part of an existing primary residence
- Maximum 1 space required in all other cases
Owner Occupancy
- Not required through 2030 (per state law extending the prohibition on local owner-occupancy mandates)
Fees
- Impact fees: Prohibited for ADUs under 750 sq ft
- Reduced fees: Pro-rata fees for ADUs 750-1,200 sq ft
- Connection fees: Must be proportional to ADU's burden on infrastructure
SB 9 (2021): Lot Splitting
Do not confuse SB 9 (2025) with the original SB 9 (2021), which allows single-family lot splitting:
- Allows splitting single-family lots into two parcels
- Allows up to 2 units per parcel (potentially 4 units total)
- Ministerial approval (no discretionary review)
- Owner-occupancy required for 3 years after split
- Minimum 60% of original lot size for each new parcel
- Cannot be used in historic districts or environmentally sensitive areas
SB 9 lot splitting combined with ADU laws can potentially allow up to 6 units on a single-family lot (2 homes + 2 ADUs + 2 JADUs).
Pre-Approved ADU Plans
California now requires cities to offer pre-approved ADU plan programs:
- Faster approval: 30-day permit processing (vs 60 days for custom plans)
- Lower design costs: No architect needed if using pre-approved plans
- Reduced uncertainty: Plans have already been reviewed for code compliance
- Growing availability: Major cities (LA, San Jose, San Diego) have active programs
Check your city's building department for available pre-approved ADU designs.
Coastal Zone ADUs (2026 Update)
Building ADUs in the California Coastal Zone has historically been more complex. The 2026 updates address this:
- By July 1, 2026, the Coastal Commission must provide clear guidance for ADU approvals in coastal areas
- Local governments must amend their local coastal programs to accommodate ADUs
- The goal is making the process faster and easier for most property owners
- Coastal development permits may still be required in some areas, but the process should be significantly streamlined
Local vs State Law Conflicts
When local ADU ordinances conflict with state law:
- State law prevails in most cases
- Local ordinances must be submitted to HCD within 60 days of adoption
- Non-compliant ordinances are void under SB 9 (2025)
- Default state standards apply when local rules are voided
- HCD enforcement has increased significantly since 2024
If you believe your city is not following state ADU law, you can file a complaint with HCD or consult with an ADU attorney.
Frequently Asked Questions
Can my city deny my ADU permit?
Under state law, ADU applications that meet objective standards must receive ministerial approval (no discretionary review or public hearings). Cities cannot deny compliant applications. If your application meets zoning, setback, size, and building code requirements, the city must approve it within 60 days.
Do I need an architect for my ADU?
Not if you use pre-approved plans from your city's program. For custom designs, you may need an architect or designer depending on project complexity. California law does not require architect stamp for residential buildings under certain size thresholds when a licensed contractor is involved.
Can I build an ADU in a homeowners association (HOA)?
California's state ADU laws override most HOA restrictions. HOAs cannot unreasonably restrict ADUs, though they may have some authority over exterior appearance. Recent legislation has strengthened homeowner rights against HOA ADU restrictions.
What is the difference between an ADU and a JADU?
An ADU is a complete, independent dwelling unit with its own kitchen, bathroom, and entrance. A JADU (Junior ADU) is created within the existing primary dwelling, is limited to 500 sq ft, and may share a bathroom with the primary home. Both are permitted on a single-family lot. See our complete ADU guide for full details.
Will the ADU laws change again in 2027?
California consistently passes new ADU legislation. The trend is toward greater permissiveness, faster permitting, and stronger enforcement. Future changes will likely expand ADU rights further, potentially including additional height allowances and further reduction in local barriers.
Related Reading
- AB 2221 ADU Rules Explained
- California ADU Laws 2026 Update
- Washington State ADU Laws 2026
- ADU Permits and Zoning: The State-by-State Guide
- How Much Does an ADU Cost in California 2026?
-- The ADU Finder Team