ADU Permit Process in California, Step by Step (2026)

In California, a city has 15 business days to tell you whether your ADU application is complete, then 60 days to approve or deny it, with no public hearing. If you use a pre-approved plan from the city's AB 1332 program, the decision is due within 30 days. Design and construction take far longer than the review itself, so most projects run 6 to 18 months from first sketch to move-in.

Key takeaways

• ›Completeness check: 15 business days, or the application is deemed complete (SB 543).
• ›Decision: within 60 days of a complete application, ministerial, no hearing.
• ›Pre-approved plans must be approved or denied within 30 days (AB 1332), and every city must offer a program.
• ›Most delays come from incomplete plans and correction cycles, not the legal deadlines.

What should you do before applying for an ADU permit?

Spend a few hours on free research before paying for drawings.

• ›Read your city's ADU rules. Start with your city page, for example Los Angeles, San Diego, or Sacramento. Check size limits, height, and anything local like design standards.
• ›Look at the pre-approved plan library. State law (AB 1332) requires every city to offer a pre-approved detached ADU plan program. Some cities, such as Garden Grove and Sacramento, offer city-owned plans free.
• ›Ask for a pre-application meeting. Many planning departments offer an informal review where you describe the project and get early feedback before you pay for full plans.
• ›Estimate fees. Use the permit fee estimator and the cost calculator.

Step 1: Who draws ADU plans, and what do they cost?

You need complete construction drawings to apply. Your options:

• ›Architect: most flexibility, best for tricky sites or custom designs, and usually the most expensive route
• ›Designer or draftsperson: less expensive and enough for most straightforward projects
• ›Prefab or modular company: plans come with the product
• ›Pre-approved plan: pick a design from your city's program, add a site plan, and customize finishes

A full set covers the site plan, floor plans, elevations, sections, foundation and framing, and Title 24 energy compliance. Incomplete plans are the most common reason applications bounce.

Step 2: How long does ADU plan review take?

Once you submit, state law sets two clocks (Gov. Code §66317, as amended by SB 543 in 2025):

1. ›Completeness: 15 business days. The city must say whether the application is complete. If it does not respond in time, the application is deemed complete.
2. ›Decision: 60 days. The city must approve or deny a complete application within 60 days. Review is ministerial, so there is no public hearing.

For plans that match a pre-approved design, the deadline is 30 days (AB 1332, Gov. Code §65852.27).

The building department reviews the drawings against the California Building Code, Title 24, and local standards, and routes them to planning, fire, and public works. If corrections come back, your designer revises and resubmits. One correction cycle is normal. Three or more usually points to weak original drawings.

Step 3: What fees do you pay when the permit is issued?

Once plans are approved, the city issues the permit and collects the rest of the fees:

• ›Building permit and plan check fees (usually based on project valuation)
• ›Mechanical, electrical, and plumbing fees
• ›School fees, but only for ADUs over 500 sq ft (units of 500 sq ft or less are exempt under SB 543)
• ›Impact fees, but only for ADUs of 750 sq ft or more, and then proportional to the main home (Gov. Code §66324)
• ›Utility connection fees, where they apply

Permit fee ranges in our city data run from $3,500–$9,000 in Bakersfield to $8,000–$35,000 in San Francisco, based on ADUByCity city data, as of 2026. Permits expire if work does not start or stalls without inspections, so ask your city how long yours stays active.

Step 4: Which inspections does an ADU need?

An inspector must sign off at each stage before work continues:

• ›Foundation: forms and rebar set, before the pour
• ›Framing: walls, floor, and roof framed
• ›Rough-in: plumbing, electrical, and mechanical before walls close
• ›Insulation: before drywall
• ›Drywall nailing: in some cities
• ›Final: everything complete

A contractor with recent local experience prepares for each one (see how to hire an ADU contractor).

Step 5: Do you need a certificate of occupancy to rent an ADU?

Yes. After the final inspection, the city issues a certificate of occupancy or final sign-off confirming the unit is legally habitable. Without it, you should not rent the unit. Insurance may not cover an unpermitted dwelling, and you risk fines and liability. If you already have an unpermitted unit, see how to legalize an unpermitted ADU.

Worked example: permit timeline in Los Angeles

Los Angeles runs the LADBS Standard Plan Program, with pre-approved designs including one city-owned plan that is free to use. Based on ADUByCity city data, as of 2026:

A custom design also adds weeks of design time up front. Other cities with 30-day paths for pre-approved plans in our data include Hayward, Sunnyvale, and Santa Rosa.

How long does the whole ADU process take?

Total: about 6 months for a smooth pre-approved project, 18 months or more for a complex site with several correction cycles. Compare city timelines on the compare page.

What causes ADU permit delays?

• ›Incomplete plans: missing details trigger correction cycles, and each one resets part of the wait.
• ›Extra reviews: coastal zones (for example Santa Monica) and historic districts (for example Pasadena) can add time.
• ›Scope changes: changing the design after approval means a revision and re-review.
• ›Failed inspections: each one costs days or weeks.

If a city misses the 15-business-day or 60-day deadline, point to Gov. Code §66317 in writing and ask for a decision. HCD also accepts reports of cities that do not follow state ADU law.

For the full legal picture, see California ADU laws and ADU setback requirements.

Sources

• ›Gov. Code §66317: ADU permit timelines (SB 543)
• ›Gov. Code §65852.27: pre-approved ADU plans (AB 1332)
• ›Gov. Code §66324: ADU impact and school fees
• ›HCD: Accessory Dwelling Units
• ›LADBS: ADU Standard Plan Program
• ›LADBS: Accessory Dwelling Unit (ADU)
• ›Fee and timeline ranges: ADUByCity city data, as of 2026