ADU permit cost and fee breakdown in Mill Valley, California
GetYourPermit’s researched permit-fee range for a detached accessory dwelling unit in Mill Valley, 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
$7,350 – $12,450
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
$9,750
Modeled at the 600 sq ft reference.
Where the money goes
These are fee components within the permit process, not separate approvals.
- Separate planning / zoning fee$400 – $700
Shown only where the City bills Planning or zoning review as a separate fee.
- Building plan check$1,450 – $2,650
The Building Division’s review of the drawings; part of the Building Permit process.
- Building permit issuance$1,900 – $3,400
The permit issuance charge; where plan check is bundled, the combined amount is carried here.
- Separate trade permits$500 – $950
Shown separately only where electrical, plumbing, or mechanical permits are billed outside a combination permit.
- School district fees$2,600 – $3,400
Possible school-district developer fees based on current thresholds and scope.
- Utility fees$300 – $850
Possible water, sewer, electrical, meter, or capacity-related charges.
- Processing, inspection & records$100 – $250
Fixed processing, inspection, records, and administrative charges.
- Surcharges, taxes & state fees$100 – $250
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 |
|---|---|---|---|
| Current residential/ADU building permit fee lookup | Verify on the City’s official website | Verify on the City’s official website | Forms, Fees & ResourcesLocation: Forms, Fees & Resources landing page and historical Building Permit Fees Effective July 1, 2025Confirms: The official source route establishes a valuation-based schedule but not the current fiscal-year numeric amounts. |
Impact fees
Development impact fees. Prohibited for ADUs of 750 sq ft or less.
| Fee | Amount | Basis | Source |
|---|---|---|---|
| Road impact fee applicability | 1% formula | Formula | Building FAQLocation: Building FAQ, Road Impact Fee paragraphConfirms: The City FAQ states the road-impact fee is 1% of permit valuation for permits valued at $10,000 or more. |
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 Mill Valley before you commit money.
City reference pages for verification
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