San Benito County, CA Accessory Structures: ADU Impact Fees (2026)
Key Facts
- Fee waiver threshold
- Under 750 sq ft
- Larger ADU fee
- Proportional to floor area
- Example rate
- 750/2,250 sq ft = 33%
- Water/sewer charges
- Still apply separately
Summary
ADUs under 750 square feet pay zero county impact fees in unincorporated San Benito County; larger units pay a fee scaled to their share of the primary home's floor area.
No county-imposed impact fees shall be charged for an accessory dwelling unit that is less than 750 square feet in size. For accessory dwelling units 750 square feet or larger, county-imposed impact fees shall be charged proportionately in relation to the square footage of the primary dwelling (e.g., the floor area of the accessory dwelling unit, divided by the floor area of the primary dwelling, times the typical fee amount charged for a new dwelling).
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2025 S-28: current through Ordinance 1078).
Full Breakdown
San Benito County waives county-imposed impact fees entirely for any accessory dwelling unit smaller than 750 square feet. Once an ADU hits 750 square feet or more, fees are charged proportionately: divide the ADU's floor area by the primary dwelling's floor area, then apply that fraction to the standard new-dwelling fee (a 750-square-foot ADU next to a 2,250-square-foot house pays 33% of the usual fee). The break covers only county impact fees, water and sewer connection or capacity charges, garbage and recycling charges, and fees from other agencies still apply on their own schedules.
Violations & Fines
Impact fees are collected as a condition of the building permit, so there's no separate violation: an applicant who understates ADU square footage to dodge the proportional fee risks permit revocation and repayment once discovered.
Frequently Asked Questions
Does a small ADU in San Benito County pay county impact fees?
How are fees calculated for a larger ADU?
Sources & Official References
Other rules in San Benito County
California rules heatmap·Compare San Benito County to another location·View the California accessory structures overview
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