Sacramento County, CA Accessory Structures: ADU Impact Fees (2026)
Key Facts
- Small-ADU exemption threshold
- under 750 sq ft
- Larger ADU fee method
- prorated to primary unit's fee
- Governing program
- SCTMFP, countywide
- Fees cannot be
- waived outside listed exemptions
Summary
Sacramento County waives its Countywide Transportation Mitigation Fee for accessory dwelling units under 750 square feet; larger ADUs pay a prorated share of the primary unit's fee.
The following Development Projects shall not be subject to the SCTMFP fee: A. Accessory Dwelling Units less than 750 square feet. ... Fee is based on the ratio of the floor area of the ADU compared to the primary unit, times the fee that would be charged on the primary unit, if the primary unit was being newly built.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4941150; v18 updated 2026-05-19).
Full Breakdown
Under Sacramento County Code § 16.91.100, ADUs smaller than 750 square feet are fully exempt from the Sacramento Countywide Transportation Mitigation Fee Program (SCTMFP) fee charged at building permit issuance. ADUs at or above 750 square feet aren't exempt outright: per the § 16.91.040 fee schedule, the fee is based on the ratio of the ADU's floor area to the primary unit's floor area, multiplied by the fee that would apply to a newly built primary unit. The SCTMFP applies countywide to all development projects in the unincorporated area (§ 16.91.050); fees can't be waived outside the listed exemptions and are remitted to the Sacramento Transportation Authority.
Violations & Fines
No building permit or certificate of occupancy is issued until any owed SCTMFP fee is paid; the County calculates the fee at permit issuance under § 16.91.050.
Frequently Asked Questions
Does my Sacramento County ADU owe a transportation impact fee?
Does the exemption apply inside Sacramento, Elk Grove, or other cities?
Sources & Official References
Other rules in Sacramento County
California rules heatmap·Compare Sacramento County to another location·View the California accessory structures overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.