San Mateo ADU Permit Fees & Cost Calculator
San Mateo homeowners can use this planning calculator to estimate ADU permit fees, plan check charges, impact fee exposure, school fees, utility costs, and other pre-development costs before speaking with the city or a design professional.
Free ADU fee calculator
Estimate local ADU fees
Step 1 of 5: Location
The MVP covers California cities with visible confidence levels and dated source tracking.
Fee overview
San Mateo fee estimates should be verified against the current city fee schedule before filing.
Garage conversions can have lower utility and site-work costs when existing services are adequate.
Detached ADUs may trigger more utility, fire access, drainage, or public works review than interior conversions.
School fees, if applicable, are usually confirmed outside the city building permit counter.
Projects over 750 sq ft need closer review for proportional impact fee treatment.
FAQs
Are San Mateo ADU fee estimates official?
No. ADUFee.com provides planning estimates only. Final fees are set by the city, utility providers, school district, and other agencies.
Do ADUs under 750 sq ft avoid impact fees in California?
California law generally protects ADUs with 750 sq ft or less of interior livable area from development impact fees, but homeowners should verify local application before budgeting.
Why can utility fees vary so much?
Water, sewer, and electric costs can depend on meter size, service capacity, lateral condition, trenching, provider rules, and whether the ADU needs a separate connection.