ADUs
How long does an ADU actually take?
We will not quote you a permit duration, because it is not ours to promise. What we can hand you is the three deadlines the city owes you.
An ADU runs in four phases: feasibility, design and engineering, permitting, then construction. Permitting is the phase nobody controls and everybody underestimates — but as of 2026 three statutory clocks run against the city rather than against you: 15 business days to tell you whether your application is complete, 60 days to approve or deny a complete application, and 30 days for a ministerial decision if you use a pre-approved plan. Those are the only durations we will state, because they are the only ones anybody can state honestly.
The three clocks, and what starts each one
| Clock | What it covers | What happens if the city misses it |
|---|---|---|
| 15 business days | Determining whether your ADU application is complete, and telling you in writing with a list of missing items (Gov. Code §66317(a)(2)(A)–(B)). New on 1 January 2026 | The application is deemed complete — §66317(a)(2)(F) |
| 60 days | Approving or denying a complete application, where there is already a dwelling on the lot (Gov. Code §66317(a)(3)) | The statutory deadline is breached; raise it in writing and escalate |
| 30 days | A ministerial decision on an application that uses the city's pre-approved ADU plan, under AB 1332 / Gov. Code §65852.27 | Same — and this is the fastest route that exists |
This clock is new, it is the only one that produces an automatic consequence, and in our experience almost no homeowner is tracking it. Note the submission date, add 15 business days, and if nothing has arrived in writing by then, say so in writing. It costs you one email and it can save you a review cycle.
The four phases, honestly described
Feasibility
Walk the lot before anyone draws anything. Usable rear-yard rectangle after setbacks, access for equipment and concrete, where the utilities come in and how far they have to travel, and whether the existing electrical service can carry another dwelling. This phase is short and it is the cheapest place to find out your lot will not take what you pictured.
Design and engineering
An architect and structural engineer produce the stamped permit set including Title 24. This phase moves at the speed of your decisions. It is the one you control most directly and the one most often extended by changing your mind late. If your city runs a pre-approved plan programme, this is the phase that can largely disappear.
Permitting
Submit, wait on the completeness determination, then plan check, corrections and resubmittal. Rarely one round. The three clocks above live here. This is the phase that varies most between jurisdictions, which is why we ask your building department rather than quoting you a number.
Construction
Site work and foundation, framing, roof and envelope, rough-in for all trades and their inspections, insulation and drywall, finishes, then final inspection and occupancy. The most predictable phase, because it is sequenced work with known dependencies.
Why we will not give you a completion date before permits
Plan-check duration is set by your jurisdiction, not by us. A single confident completion date offered before plan check is a sales tool, not a schedule — and the builder who gives you one has quietly moved the risk of a date they do not control onto their own credibility, which means they will be managing that instead of managing your job.
What you should get instead is a schedule that names the phases, marks which dates depend on the city rather than on us, identifies the long-lead items early, and gets updated when something moves.
What actually moves an ADU schedule
- The pre-approved plan question, asked early enough to matter. Every California city must run an AB 1332 programme. Where one exists, it can take the plan cost off the project and collapse plan check into a 30-day ministerial clock. Ask before anyone starts drawing, not after.
- Utility coordination. Service connections and upgrades run on the utility's timeline. On a detached unit in San José the separate PG&E meter is its own process and it does not move faster because your framing is done.
- An electrical service that cannot carry the load. If the existing service is undersized, an upgrade — typically $7,000–$10,000 — becomes the first item in the project rather than a surprise in the middle of it.
- Late selections. The most common cause of slippage and the most controllable one.
- Site conditions found below grade. Less common than on a remodel, but soils and buried surprises are real on ADU foundations.
- Inspection holds. Work stops until the inspector arrives and passes it. That is by design and it is not padding.
You should be able to see where the job is without asking. On our projects that means photos, schedule and selections through BuilderTrend — the same view we have. How we work →
Common questions
How long does it take to get an ADU permit in California?
What is the fastest way to permit an ADU?
Why won't you give me a completion date before permits?
What delays ADU projects the most?
What happens if the city misses the 15-business-day deadline?
Where to go next
Written by the team at Elusive Construction, a licensed California general contractor (B #1112902) building in Santa Clara and San Mateo counties. General information about how residential construction works — not legal advice. For your specific contract, talk to an attorney.
Also Worth Reading
The rest of what we publish
Cost guides
What an ADU, an addition, a kitchen or a whole house actually costs here, and what moves each number.
Our own projects
Two jobs written up start to finish, including what we found once the walls were open.
Paying for it
Renovation lenders we work with. We take no referral fee, and we never quote you a rate.
Where we build
Sixteen cities across two counties, and what genuinely changes at each city line.
Have a project you want priced honestly?
Book a Project Discovery Call and we'll tell you what's realistic — scope, budget and timeline — whether or not we're the right builder for it.