An ADU permit in California is a ministerial approval: if your plans meet the objective standards, the city has to issue it, with no hearing and no neighbor vote. The process still has seven steps and a few places it stalls. Here is the whole thing.
- 15 business days for the city to tell you whether the application is complete (SB 543, 2026). Miss it and the application is deemed complete.
- 60 days from a complete application for approval or denial. Miss it and the ADU is deemed approved.
- 30 days if you use a city pre-approved plan set (AB 1332).
Step 1. Confirm what you can build
Zoning, lot lines, setbacks, fire severity zone, easements, and the existing building footprint decide where an ADU can go and how big it can be. This is the step Parcy does in seconds from an address, and the one most owners skip and pay for later in redesign.
Step 2. Plans and engineering
You need architectural plans, structural calculations, Title 24 energy compliance, and often a site plan with utilities. Budget $8,000 to $30,000, or use a pre-approved plan from your city to cut most of that. Pre-approved plans still need a site plan for your lot.
Step 3. Submit to the building department
Most cities now accept ADU applications online. The city must determine completeness within 15 business days and give you a written list of anything missing. On resubmittal it can only review the items it already flagged.
Step 4. Plan check
Plan check comments are where the 60 days get spent. Common ones: fire separation distance, sprinkler triggers when the main house has them, sewer lateral sizing, and electrical service capacity. A good ADU designer anticipates these. If review drags past 30 business days on a project of ten or fewer units, AB 253 lets you hire a certified private plan checker.
Step 5. Fees and permit issuance
Plan check and permit fees typically run $5,000 to $15,000. Impact fees are waived for ADUs under 750 square feet and school fees for units under 500. Utility connection fees vary by district and are the most common surprise.
Step 6. Construction and inspections
Foundation, framing, rough plumbing and electrical, insulation, drywall, and final. AB 1308 now requires final inspections within 10 business days of a completion notice on small projects.
Step 7. Certificate of occupancy
The CO is what makes the unit legal to rent, insurable, and countable on an appraisal. Record the JADU deed restriction if you built one.
Permits for unpermitted ADUs
If the unit already exists and was built before 2020, AB 2533 gives you a health-and-safety-only path to legalize it with fees waived.
Start with step one. Run your address in Parcy, or send it to our team and we will carry the permit through.
Frequently asked questions
How long does it take to get an ADU permit in California?
A complete application must be approved or denied within 60 days. Completeness must be determined within 15 business days under SB 543. Pre-approved plans must be acted on within 30 days.
How much does an ADU permit cost?
Plan check and permit fees typically run $5,000 to $15,000 depending on the city and unit size. Impact fees are waived under 750 square feet.
Do I need an architect for an ADU permit?
You need stamped plans and structural engineering, which can come from an architect, a designer with an engineer, or a city pre-approved plan set plus a site plan.
Informational only. Not legal, architectural, or investment advice. Confirm current rules with your local planning department.