The California ADU Permit Process: Every Step from Plans to Approval

Ministerial means no hearing, no neighbor veto

Start with the most important fact: an ADU permit California is reviewed ministerially. The reviewer measures your plans against objective, written standards — setbacks, height, size, egress — and if you meet them, they must approve. There is no hearing no neighbor veto, no design review board, and no discretionary "does this fit the neighborhood character" judgment. That single change is why the process is so much faster than a typical remodel or addition.

How to get an ADU permit: the sequence

Here is how to get an ADU permit, step by step:

1. Prepare the plan set. Site plan, floor plans, four elevations, sections, structural calculations, and a Title 24 energy form. Hillside lots add a soils/geotech report.
2. Submit for plan check. The city routes your set through building, and where relevant, planning and utilities.
3. Clear the completeness check. The city confirms your application is complete — on a strict timeline (below).
4. Address plan-check comments. If corrections come back, you revise and resubmit.
5. Receive approval and pull the permit. Pay fees, get the stamped set, and construction can begin.

The two phases people conflate are the ADU plan check (does the drawing meet code?) and the completeness check (is the application whole?). They are different clocks, and knowing both is how you keep the city honest.

Coastal, historic, and fire-zone caveats

Ministerial approval is nearly universal, but a few overlays add a wrinkle. In the coastal zone, a coastal development permit can apply on top of the ADU approval. In a designated historic district, exterior changes may face extra objective standards. And in a very-high fire hazard severity zone, wildfire construction standards apply to the build. None of these overturn your right to the unit — they add objective requirements you design to. If your lot sits in one of these overlays, flag it at the design stage so the plan set accounts for it and the completeness check still passes on the first pass.

The 15 business day completeness check

New for 2026: after you submit, the city has a 15 business day completeness check to tell you whether your application is complete. If they say nothing in that window, the application is deemed complete by operation of law. If they do respond, they must send a written ADU incompleteness letter that lists every deficient item at once. They cannot dribble out new problems on your second submission — when you resubmit the flagged items, the city may only review those items, not invent fresh ones. That rule alone prevents the endless-revision trap that used to bury ADU applicants.

The 60 day ADU approval clock

Once your application is complete, the city must approve or deny within 60 days. This is the 60 day ADU approval deadline, and it has teeth: if the city blows the deadline on a complete, compliant application, the permit is deemed approved. Combined with the completeness rule, this is what makes the ADU approval timeline something you can actually plan a construction loan and a contractor start date around.

Pre-approved plans: the fastest ministerial ADU permit

If speed is the priority, use a pre-approved plan. Under AB 1332, every California city must run a program of ADU pre-approved plans — standardized designs the city has already reviewed and posted online. Building from an AB 1332 pre-approved ADU plan means the design work is done and the city's review shrinks dramatically, often to about 30 days. It is the closest thing to a shortcut in the entire process, and it turns a ministerial ADU permit into a nearly turnkey approval. The tradeoff is less design flexibility — you build one of the city's shapes — but for a rental unit that is usually a fine trade.

Information only; not a commitment to lend and not legal advice. Rules summarized here reflect California state law effective in 2026; local ordinances and site conditions vary. Confirm specifics with your city and a licensed professional before you build.

What to submit to pass plan check the first time

Most delays are self-inflicted — an incomplete set that trips the completeness check. Bring these and you sail through: an accurate site plan showing setbacks and the existing structures; complete floor and roof plans; four elevations; building sections; stamped structural calculations; the Title 24 (CF-1R) energy compliance form; and, for hillside or expansive-soil lots, a soils report. Clean sets get clean approvals.

What triggers an incompleteness letter — and how to avoid it

The completeness check is pass/fail, and failing it is the number-one cause of permit delay. Cities issue an incompleteness letter when the plan set is missing a required drawing, when the structural calculations aren't stamped, when the Title 24 energy form is absent, or when the site plan doesn't clearly show setbacks and existing structures. The fix is boring and effective: submit a complete, professionally prepared set the first time. Because the city must list every deficiency in that first letter — and can't add new ones later — a complete initial submission effectively locks the city into a single, fast review cycle.

Permit fees and what you pay at issuance

When the permit is approved you pay plan-check and building-permit fees, and for larger units any proportionate impact fees. These are modest next to construction, and the biggest ones — impact fees — are waived entirely for units under 750 square feet and for all JADUs. Don't let fee anxiety stall the application; the full fee picture, including the exemptions, is broken down in ADU Utilities, Fees & Costs in California.

Frequently Asked Questions