In California, the statutory answer is 60 days. Under the statewide accessory dwelling unit (ADU) law administered by the Department of Housing and Community Development (HCD), a local agency must approve or deny a complete ADU application ministerially, without a hearing, within 60 days of receiving it. That is the whole review window, and it is enforceable.
The useful answer to the ADU permit timeline question is different: 60 days plus your front end. The clock does not start when you email the drawings. It starts when the application is complete, and getting to complete is where the calendar actually goes.
Outside California, there is no statewide clock in most states, and an ADU is reviewed like any other small residential addition on the jurisdiction’s published turnaround.
What does California’s 60-day ADU permit clock cover?
It covers the agency’s review and decision on a complete application. Ministerial means staff apply objective standards and issue the permit if you meet them. No design review board, no discretionary finding, no public hearing.
Two consequences matter for scheduling. First, the agency cannot park your application indefinitely while a planner forms an opinion about the roof pitch. Second, if the agency does not act within the window, the application is deemed approved by operation of law in the circumstances the statute describes. Nobody wants to rely on that, and clients love hearing it exists.
What the clock does not cover: the completeness determination itself, utility connections handled by a separate district, school or impact fees where they apply, and anything you resubmit after a correction letter. Corrections restart practical progress even where they do not formally restart the statute.
HCD’s ADU Handbook is the reference to keep open. It is written for local staff as much as for designers, which makes it unusually direct about what a city may and may not require.
What has to happen before the clock starts?
This is the part clients underestimate, so put it in the proposal as a list rather than a duration:
- A survey or a reliable existing-conditions plan. Setbacks, easements, and the septic or sewer location decide the design.
- Zoning confirmation. Lot eligibility, maximum size, height, setback, and whether the unit is attached, detached, or a garage conversion.
- Utility confirmation. Water meter capacity, panel capacity, and whether a separate service is required or prohibited.
- A complete drawing set. Site plan, floor plan, elevations, sections, structural, and the state energy compliance documentation.
- Owner paperwork. Signatures, deed restrictions where required, and fee payment. This is the item that most often sits for two weeks.
None of that is glamorous. All of it is the difference between a 60-day review and a four-month one.
How long does an ADU permit take outside California?
It depends on whether the state or city has adopted an ADU ordinance with objective standards, and on the local plan check queue. Many jurisdictions publish their turnaround times for residential permits, and that published number is your best planning input. Ask for it at the counter or check the department’s website before you commit to a schedule.
Two structural facts shape the review anywhere. The International Code Council (ICC) publishes the I-Codes on a three-year cycle, with the 2024 edition current and the 2027 edition in development, but the governing edition is whatever your jurisdiction adopted. And in California, the 2025 California Building Standards Code (Title 24) took effect January 1, 2026, so a set drawn to the prior edition will come back.
AARP’s Livable Communities ADU material (2022 guides) is the most useful plain-English resource to hand a homeowner client, mainly because it sets expectations about process before you have to.
Why do ADU permits stall?
Rarely because of the building. Almost always because of the site or the paperwork.
The recurring five: an existing structure with no permit history that the city discovers during review, a septic system that needs county health approval, a fire access or hydrant flow requirement triggered by the added unit, a utility upgrade the client did not budget, and a garage conversion where the slab and footings do not meet current requirements.
There is also the quiet one. California permitted nearly 27,000 ADUs in 2023, which means the plan checkers reviewing yours have seen hundreds. They know the shortcuts, and they know which sheets you skipped. A set that looks like every other conversion set gets read faster than a clever one.
How should you schedule and price ADU permitting?
Schedule it as three blocks, not one: pre-application work, the statutory or published review window, and one correction cycle. Give the client a date for each block rather than a single permit date. When something slips, you are moving one block instead of breaking a promise.
Price it the same way. An ADU is a small fee with a full-size permit process, which is the classic margin trap for residential practices. Deltek’s Clarity A&E Industry Study 2026 (47th edition) puts firm-wide utilization just under 60% and operating profit on net revenue at 16.7%. Two unpriced correction rounds on a $14,000 ADU fee is the entire profit on that project and part of the next one. If you are deciding how to structure the fee at all, fixed fee vs. hourly vs. percentage of construction is the argument worth having before you send the proposal, not after.
Say the number out loud at the first meeting: 60 days of review, plus roughly the same again for everything that has to happen before and after it, assuming one correction round and a client who returns paperwork the week you send it. Homeowners can hear that. What they cannot forgive is a permit date that moves three times.
For the wider explanation of what all these review steps are doing, why permitting takes so long covers the structure behind the calendar.
AECPulse Project Manager tracks each ADU through its own jurisdiction with the application date, the statutory clock, and the correction rounds logged, so the homeowner’s weekly status question takes one glance rather than one phone call.