ADU permit cost and fee breakdown in Modesto, California
An early-budgeting estimate of the permit-related fees an accessory dwelling unit is likely to incur in Modesto. These are not official figures.
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ADU size
California generally exempts ADUs under 750 sq ft from development impact fees, so the 749 / 750 / 751 steps are worth comparing.
Estimated total
Estimated total permit fees at 750 sq ft
$8,050 – $35,350
Assumed construction valuation
$270,000
Used only to compute valuation-based fees. It is not a construction quote.
Where the money goes
- Building permit$1,500 – $4,000
The core permit issued by the city building department.
- Plan check$1,000 – $2,500
Review of your drawings for code compliance.
- Impact fees$3,000 – $12,000
Development impact fees. Often waived for ADUs under 750 sq ft.
- School district fees$0 – $5,000
Developer fees charged by the local school district.
- Utility connection$2,000 – $10,000
Water, sewer, and electrical connection or capacity charges.
- Inspection$400 – $1,200
Field inspections during construction.
- Technology & surcharges$50 – $250
Records, technology, and general plan surcharges.
- Other$100 – $400
Fees that do not fit the categories above.
The darker segment is the low end of the range; the full bar is the high end.
Read before you budget
- Most fee lines are working estimates rather than verified published city rates. Confirm every line with the city before budgeting.
- Totals do not vary by ADU size for this city, so the size selector will not change the estimate.
Fee items
Building permit
The core permit issued by the city building department.
ADU building permit fee estimate
$1,500 – $4,000
Estimated range
Accessory Dwelling Unit (ADU) Building Permit Fee Estimate
Plan check
Review of your drawings for code compliance.
ADU Plan Check Fee
$1,000 – $2,500
Estimated range
Impact fees
Development impact fees. Often waived for ADUs under 750 sq ft.
California ADU impact-fee exemption under 750 sq. ft.
$0
Flat fee
Accessory Dwelling Unit (ADU) Building Permit Fee EstimateADU Impact Fee (750 sq. ft. or larger)
$3,000 – $12,000
Estimated range
School district fees
Developer fees charged by the local school district.
ADU School District Developer Fee
$0 – $5,000
Estimated range
Utility connection
Water, sewer, and electrical connection or capacity charges.
ADU Utility Connection and Capacity Fee
$2,000 – $10,000
Estimated range
Inspection
Field inspections during construction.
ADU Building Inspection Fee
$400 – $1,200
Estimated range
Technology & surcharges
Records, technology, and general plan surcharges.
ADU Technology Surcharge
$50 – $250
Estimated range
Other
Fees that do not fit the categories above.
City of Modesto ADU permit application / fee payment process
$100 – $400
Estimated range
Accessory Dwelling Units - Modesto, CA
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 Modesto before you commit money.
City reference pages for verification