California has spent nearly a decade making ADU permits faster and more predictable. The state requires ministerial (non-discretionary) review, so you get no public hearings and no neighbor vetoes over a compliant project. It also sets firm deadlines. Here's how the process works in 2026, step by step.
Our sources are the California Department of Housing and Community Development's ADU Handbook (March 2026, including its 2026 addendum) and Government Code sections 66310–66342. Local procedures vary, so always check your city's ADU page.
Step 1: Feasibility
Before you pay for design, find out what your lot allows:
- Zoning: single-family or multifamily, and any overlays such as coastal, historic, fire or hillside.
- Setbacks: state law generally caps side and rear setbacks for new ADUs at 4 feet.
- Utilities: where your sewer lateral runs, the size of your electrical panel, and your water meter.
- Easements and existing structures: anything unpermitted may need attention. See legalizing an unpermitted ADU.
Many cities offer free pre-application meetings or online ADU checkers.
Step 2: Choose a path, custom or pre-approved
Under AB 1332, every local agency had to create a program to pre-approve ADU plans by January 1, 2025. Using a pre-approved or standard plan can reduce design costs and review time. See our list of verified pre-approved plan programs.
Step 3: Design and documents
A typical ADU submittal includes:
- a site plan with setbacks and utility routing
- floor plans, elevations and sections
- structural calculations
- a Title 24 energy compliance report
- a soils report, when required
- fire sprinkler details, which are required only if the main house is sprinklered, per HCD guidance
Step 4: Submit, and the completeness clock starts
New for 2026: a permitting agency must decide whether your application is complete and notify you in writing within 15 business days (Gov. Code section 66317(a)(2)(A), per HCD's 2026 addendum). If it's incomplete, the agency must list the missing items and explain how to fix them. Agencies must also offer an appeal process for incompleteness determinations and denials, with a final written decision within 60 business days of the appeal.
Step 5: Plan check, and the 60-day decision
Once your application is complete, the agency must approve or deny it within 60 days (Gov. Code section 66317). If it doesn't act in time, the application is deemed approved. If it denies the application, it must give you a full set of comments explaining how to fix the problems. Coastal zone ADUs follow a separate 60-day timeline for the coastal development permit.
Expect one or two rounds of corrections. Builders who know your city's plan checkers save real time here.
Step 6: Fees
- Impact fees: none for ADUs of 750 sq ft or less, or JADUs of 500 sq ft or less. Above that, fees must be proportional to the size of the main house (Gov. Code section 66311.5).
- Utility connection fees: generally none for ADUs converted within existing space, and for JADUs.
- School fees: typically only above 500 sq ft.
- Plan check and permit fees: still apply, and vary by city.
Step 7: Build and inspect
Typical inspections include the foundation, underground plumbing, rough framing, electrical, plumbing and mechanical, insulation, drywall nailing, and a final. Your contractor schedules them. At final, you receive a certificate of occupancy or a final sign-off.
Step 8: Address and utilities
Your city or county assigns the new unit an address. If you're adding a separate meter, the utility handles that separately, and it can take weeks.
Rules cities cannot impose
HCD's Handbook lists many local requirements that conflict with state law, including:
- owner-occupancy requirements for ADUs
- replacement parking when a garage or parking space is converted
- discretionary design review or public hearings
- denying an ADU because of unrelated nonconforming conditions on the lot that aren't a health or safety issue
If you hit one of these, cite the code section politely and ask for a supervisor. You can also contact HCD's Housing Accountability Unit.
Ordinances that are void
Under 2025 legislation (SB 9 of 2025), a local ADU ordinance that isn't submitted to HCD within 60 days of adoption, or whose agency doesn't respond to HCD findings within 30 days, is null and void. In that case, only State ADU Law applies.
How long does the whole thing take?
Most Southern California ADUs take 2–6 months from design start to permit issuance, then 4–10 months to build. See how long it takes to build an ADU.
Frequently asked questions
How long does a city have to approve an ADU permit in California?
60 days from a complete application. If the agency does not act, the application is deemed approved. As of 2026, agencies must also decide whether an application is complete within 15 business days.
Do ADU permits require a public hearing?
No. ADU applications that meet the standards must be reviewed ministerially, without discretionary review or hearings.
Can my city charge impact fees on an ADU?
Not on ADUs of 750 square feet or less. Larger ADUs can be charged fees proportional to the size of the primary home.
Do I need fire sprinklers in my ADU?
Only if the primary home is required to have sprinklers, according to HCD guidance.
What happens if my city denies my ADU?
The city must give detailed comments explaining how to fix the deficiencies, and as of 2026 it must offer an appeal process with a written decision within 60 business days.
This page is general information, not legal, tax or financial advice. Costs vary by property and builder. Images are AI-generated illustrations. Last updated November 2026.