An ADU permit confirms your accessory dwelling unit meets local zoning, building, and safety code before you build. Nationally, expect 6 to 16 weeks from application to approval and $3,000 to $12,000 in fees, though both vary heavily by city.
Getting an ADU approved is rarely the part that surprises people. It’s everything wrapped around it: the zoning check nobody mentioned, the separate electrical permit that shows up three weeks after you thought you were done, the plan checker who wants a revision because your setback math used the wrong lot line. I’ve walked this process in enough different counties now that I’ve stopped expecting it to look the same twice.
That said, the shape of it is more universal than homeowners expect. The paperwork differs. The order of operations doesn’t.
What an ADU Permit Actually Is
An ADU permit isn’t one document. It’s usually a zoning or land use approval stacked on top of a building permit, and often a handful of separate trade permits (electrical, plumbing, mechanical) that get pulled once construction actually starts.
Cities bundle these differently. Some hand you one combined ADU packet and one clock. Others make you track three or four separate approvals, each with its own queue and its own reviewer. Nobody tells you which kind of city you’re in until you’re already standing in line.
The Permit Process, Step by Step
Strip away the local variation and almost every jurisdiction runs the same five stages, just at different speeds.
Pre-application check. Before you draft anything, confirm the lot’s zoning, size, and setback rules. Skip this and you can spend real money on a design that never had a shot.
Application submittal and completeness review. You submit the packet: site plan, floor plan, elevations, sometimes a survey. The city checks that it’s complete, not that it’s approvable. Those are different reviews, and homeowners regularly confuse them.
Plan review. Plan checkers go through the drawings against building code, fire code, and zoning. This is where most of the calendar time actually goes, and it’s the stage that varies most by city.
Corrections and resubmittal. Almost nobody sails through on the first pass. Expect at least one round of corrections, small stuff like missing dimensions, or bigger stuff like a structural detail the engineer needs to redo.
Permit issuance. Once corrections clear and fees are paid, the permit issues and you can legally start construction. Trade permits (electrical, plumbing, mechanical) typically get pulled after this point, not before, which is where a lot of “I thought I was done” confusion comes from.
| Stage | Typical duration | What happens |
|---|---|---|
| Pre-application check | 3 to 7 days | Confirm zoning, lot size, and setbacks before you draft anything |
| Application submittal & completeness review | 1 to 3 weeks | City checks the packet is complete, not that it’s approvable |
| Plan review (first round) | 2 to 6 weeks | Plan checkers review against building, fire, and zoning code |
| Corrections & resubmittal | 1 to 3 weeks | Most projects get at least one correction round before approval |
| Permit issuance | A few days to 1 week | Fees are paid and the permit issues once corrections clear |
Source: ADU Wizard Data Hub
Add it up and you’re usually looking at 6 to 16 weeks from a complete application to a permit in hand. That’s before a shovel touches dirt. Construction and inspections run separately, on their own timeline, once the permit is issued.
Now, the fees. This is the part people budget for last and regret it.
| Fee component | Typical range | Notes |
|---|---|---|
| Plan check / plan review | $500 to $2,500 | Pays for staff time reviewing your drawings, not a guarantee of approval |
| Building permit fee | $1,500 to $4,000 | Covers inspections through final sign-off |
| Impact / development fees | $0 to $5,000 | Many cities waive or reduce these under a size threshold, often around 750 sq ft |
| Utility connection or capacity fees | $500 to $3,000 | The one most homeowners forget to budget for |
| School or special district fees | $0 to $1,500 | Only kicks in above certain sizes in some jurisdictions |
Source: ADU Wizard Data Hub
Notice that impact fees, usually the single biggest line item, get waived or reduced under a size threshold in a lot of places. That’s not a rounding error. It’s the reason so many ADU projects cluster right under 750 square feet.
If you want the actual math for your build instead of national ranges, our Data Hub breaks out permit costs and timelines by state, and it’s a better starting point than any single number in this article.
What Changes City to City
Here’s the honest version: the national ranges above are a starting point, not a promise. The permit process is set by state law but run by a local department, and that combination is where all the variation lives.
More states have written statewide ADU rules than most homeowners realize, and a growing number set hard deadlines for how long a city can sit on an application. California’s ADU Handbook requires agencies to determine whether an application is complete within 15 business days, with a 60-day clock on appeals, among the tightest statutory timelines in the country. Washington State’s guidance sets its own floor: two ADUs allowed per lot, and impact fees capped at half of what the primary home pays. Neither state tells you what your specific city’s plan review queue looks like right now, because that part is still entirely local.
That’s the gap this whole section of the site is built to close. Whether your city runs ministerial, by-right review or still routes ADUs through a discretionary hearing changes your timeline more than almost anything else. Whether it has a pre-approved plan program can cut weeks off. Whether it sits inside a historic district, coastal zone, or hillside overlay can add a whole extra layer of review that the state numbers above don’t account for at all.
Look up your state and city below for the specifics: typical local timeline, typical fees, and which department you’re actually dealing with.
Common Permit Mistakes I See
Most of these have nothing to do with the design. They’re process mistakes, and they’re avoidable once you know they’re coming.
Not confirming utility capacity before submitting
Homeowners design the whole unit, submit, and then find out the sewer lateral or water service can’t support a second dwelling without an upgrade. That’s not a plan review comment, it’s a redesign, and it usually surfaces late.
Assuming “ADUs are legal here” means no design review
Ministerial approval is the default in a lot of places now, but overlay districts still apply on top of it. Historic review, coastal commission sign-off, hillside grading rules: none of that disappears just because the base zoning allows ADUs by right.
Treating a pre-approved plan as permit-ready on day one
Standard plans genuinely save time, but almost every city still requires a site-specific supplement: foundation type, drainage, grading. Skip that step and the “pre-approved” plan sits in the same queue as a custom one.
Forgetting that trade permits are separate
The building permit is not the finish line. Electrical, plumbing, and mechanical permits usually get pulled after, sometimes by your contractor and sometimes by you, and each one has its own inspection. I’ve seen homeowners think they’re done and then get surprised by a fourth permit process, weeks after the ADU permit issued.
Starting work before the permit is actually issued
I get why it happens, contractors are booked out and homeowners want to lock in a schedule. But starting on a verbal “should be fine” instead of the issued permit is how projects get red tagged mid-framing, which costs far more time than waiting the extra week would have.
Frequently Asked Questions
How long does an ADU permit take?
Most ADU permits take 6 to 16 weeks from a complete application to issuance. Ministerial, by-right cities with pre-approved plan programs tend to land at the shorter end. Cities running discretionary review, or lots inside a historic or coastal overlay, tend to run longer. Check your specific city’s page for a tighter estimate.
How much does an ADU permit cost?
Permit-related fees typically run $3,000 to $12,000 nationally, covering plan check, the building permit itself, impact fees, and utility connection charges. Impact fees are the biggest swing factor, and many jurisdictions waive or reduce them for ADUs under roughly 750 square feet.
Do I need an architect to pull an ADU permit?
Not always. Plenty of jurisdictions accept a licensed designer’s stamped drawings, and pre-approved plan programs exist specifically so you don’t need a full custom architectural set. Detached units on complicated lots, or anything requiring structural engineering, usually benefit from one anyway.
Can I pull my own ADU permit as the homeowner?
In most places, yes, an owner-builder permit is an option, though it puts you on the hook for every inspection and every code question directly. I’d only recommend it if you’re genuinely comfortable managing plan review corrections yourself. Most homeowners are better served letting their designer or contractor pull it.
What gets ADU permit applications rejected?
Incomplete utility information, setback or lot coverage errors, and missing structural details account for most of what I’ve seen come back. A completeness review catches the obvious gaps; the plan review round is where the real substance issues show up, which is exactly why the corrections stage exists.
If I were starting an ADU permit today, I’d call the planning department before I hired anyone, not after. Ask three questions: is review ministerial or discretionary here, is there a pre-approved plan program, and what’s the current plan review queue. That one phone call tells you more about your real timeline than any national guide, including this one. From there, our ADU cost guides and financing options cover what happens once the permit’s in hand, and if you’re weighing whether the investment is worth it at all, our look at ADU property value is the honest version of that question.
Browse ADU permits by location
Pick your state for permitting department contacts and a full timeline breakdown, then drill into a specific city where we cover one.
California
California's ADU law guarantees ministerial approval within 60 days, not a suggestion. Four 2026 bills tighten completeness deadlines, size measurement, and fees. Cities still control actual speed on the ground, and whether their own ordinance is even legal yet.
Oregon
Oregon requires cities over 2,500 people to allow at least one ADU by right, with no parking or owner-occupancy requirement. There's no ADU-specific approval clock; cities fall back to the general 120-day rule. Most permits move faster than that ceiling in practice.