ADU permit cost and fee breakdown in Napa, California
GetYourPermit’s researched permit-fee range for a detached accessory dwelling unit in Napa, with category estimates and direct reference links used in our investigation.
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ADU size
California prohibits development impact fees for ADUs of 750 sq ft or less, so the 749 / 750 / 751 steps are worth comparing.
Estimated total
GetYourPermit researched range at 750 sq ft
$3,135 – $13,535
This estimate combines our fee-schedule research and project-planning experience. Actual charges vary by parcel, plans, valuation, utilities, and outside agencies.
Typical planning amount
$8,835
Modeled at the 600 sq ft reference.
Where the money goes
These are fee components within the permit process, not separate approvals.
- Building plan check$701
The Building Division’s review of the drawings; part of the Building Permit process.
- Building permit issuance$1,424
The permit issuance charge; where plan check is bundled, the combined amount is carried here.
- School district fees$500 – $3,300
Possible school-district developer fees based on current thresholds and scope.
- Utility fees$500 – $8,000
Possible water, sewer, electrical, meter, or capacity-related charges.
- Surcharges, taxes & state fees$10 – $110
Percentage surcharges, construction taxes, and State-mandated charges.
The darker segment is the low end of the range; the full bar is the high end.
Published fee references
Building permit issuance
The permit issuance charge; where plan check is bundled, the combined amount is carried here.
| Fee | Amount | Basis | Source |
|---|---|---|---|
| ADU/JADU Building Permit fee | $2,125 | Flat fee | City of Napa Master Fee ScheduleLocation: Master Fee Schedule 2.1.36, ADU/JADU Building Permit FeesConfirms: The City’s current fee schedule has a dedicated $2,125 ADU/JADU row through 1,200 square feet and identifies the included review layers. |
Impact fees
Development impact fees. Prohibited for ADUs of 750 sq ft or less.
| Fee | Amount | Basis | Source |
|---|---|---|---|
| ADU under-750-sq-ft impact-fee rule | Verify on the City’s official website | Verify on the City’s official website | City of Napa Master Fee ScheduleLocation: Master Fee Schedule 12.0 Development Impact Fees; City ADU pageConfirms: The current schedule has multiple project-dependent impact and capacity layers, while the live ADU page does not establish a single current total. |
These are estimates, not official fees
Use these figures for early budgeting only. They are not a quote, not a government fee determination, and not legal advice. Actual fees depend on your parcel, your plans, your construction valuation, your utility provider, and the fee schedule in force on the day your permit is issued. Confirm every number with Napa before you commit money.
City reference pages for verification
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