Sacramento County

The Sacramento County Department of Community Development — Planning & Environmental Review (PER) and Building Permits & Inspection (BPI) divisions — is the single-point-of-contact for ADU permits on parcels in unincorporated Sacramento County. The unincorporated area covers approximately 596 square miles (roughly 59% of the county's 994 sqmi land area) and includes densely developed urban-fringe communities (Arden-Arcade, Carmichael, Fair Oaks, Orangevale, North Highlands, Rio Linda, Elverta, Antelope, Rosemont, Florin, Vineyard, Parkway, Fruitridge Pocket), suburbanizing unincorporated areas (Wilton, Herald, Sloughhouse, Rancho Murieta), rural agricultural districts (Delta communities of Walnut Grove, Ryde, Locke, Hood, Courtland, Clarksburg, Freeport), and foothill-transition lands near Folsom Lake (Gold River, Mather, Rancho Seco fringes). The seven incorporated cities — City of Sacramento, Citrus Heights, Elk Grove, Folsom, Galt, Isleton, and Rancho Cordova — permit their own ADUs independently. PER combines planning / zoning review, building plan review, grading and drainage review, fire-district referral (unincorporated areas are served by the Sacramento Metropolitan Fire District, Cosumnes CSD Fire Department, Galt FPD, Wilton FPD, Herald FPD, Courtland FPD, Walnut Grove FPD, or the River Delta FPD depending on location rather than a city fire department), and environmental review (CEQA is normally exempt for ministerial ADUs per Gov. Code 65852.2(f) and Pub. Res. Code 21080(b)(8)).

Process overview: ADU approval in unincorporated Sacramento County is a ministerial combined zoning / building / fire / environmental review. Typical sequence: (a) applicant completes the PER ADU pre-application checklist and verifies parcel zoning via the county's ParcelViewer GIS and zoning-map layer; (b) applicant submits an ADU Building Permit application through ACT Online with site plan, floor plans, elevations, Title 24 energy-compliance documentation, structural plans (for detached), and a Fire Safety Element attestation if the parcel is in a Very High Fire Hazard Severity Zone; (c) PER zoning confirms ADU type eligibility, size, setbacks, height, and any overlay triggers (Delta Primary Zone, Williamson Act, ALUCP, NBHCP, historic, biological); (d) BPI building plan check reviews for California Building Code, California Residential Code, California Energy Code, and CALGreen compliance; (e) the applicable fire district (Sacramento Metro Fire, Cosumnes CSD Fire, Galt FPD, Wilton FPD, etc.) reviews for defensible space, water supply (minimum fire flow), and access (driveway width, turnarounds) for parcels outside hydranted-water service; (f) the Sacramento Area Council of Governments (SACOG) Airport Land Use Commission reviews ADUs within Airport Influence Areas for Mather Field, Sacramento Executive, Sacramento International, and Franklin Field; (g) Delta Protection Commission advisory review applies to ADUs within the Delta Primary Zone; (h) Natomas Basin Habitat Conservation Plan mitigation fee applies to ADUs within the Natomas Basin; (i) permit issuance, construction, inspections, certificate of occupancy. The ministerial 60-day clock (Gov. Code 65852.2(b)) starts on application acceptance as complete; overlay-triggered sub-reviews (ALUC, Delta, NBHCP) run in parallel and do not extend the ADU review itself beyond state limits.

Impact fees: Sacramento County aligned its impact-fee schedule to SB 13 (2019) and subsequent state fee legislation. ADUs under 750 sqft are exempt from all county impact fees (Transportation / Roadway Fee, Park Fee, Fire Facility Fee, Habitat Conservation Fee where applicable, Drainage Fee). ADUs 750 sqft or larger pay impact fees proportional to their size as a fraction of the primary dwelling per Gov. Code 65852.2(f)(3). Building-permit fees, plan-check fees, and fire-district plan-review fees are separate from impact fees and apply at cost-recovery rates regardless of ADU size. Sewer (Sacramento Regional County Sanitation District — SacSewer — or one of the Delta-area sanitation districts for the unincorporated Delta, or on-site septic for rural parcels), water (Sacramento County Water Agency, Carmichael Water District, Fair Oaks Water District, Orangevale Water Company, Rio Linda / Elverta Community Water District, Sacramento Suburban Water District, Citrus Heights Water District — which also serves unincorporated fringes — Galt Irrigation District, Clay Water District, or on-site well for rural parcels), and school fees (Sacramento City USD, San Juan USD, Elk Grove USD, Folsom-Cordova USD, Galt Joint Union ESD, Galt Joint Union HSD, Twin Rivers USD, Natomas USD, Center Joint USD, Robla ESD, Arcohe ESD, River Delta USD, etc.) are administered by the respective district authorities, not the county. The 750-sqft-ceiling ADU is a dominant cost-minimization design in unincorporated Sacramento County because of the hard impact-fee cutoff. Within the Natomas Basin, the NBHCP mitigation fee applies on top of the standard fee package for in-basin parcels. (schedule)

The Sacramento County Assessor maintains parcel-level assessment records for all real property in Sacramento County, including parcels inside all seven incorporated cities. California is a statewide Proposition 13 jurisdiction: real property is assessed at the lower of (a) factored base-year value (1975 or last change-in-ownership / new-construction value, escalated at the lesser of 2% or CPI annually) or (b) current fair market value under Prop 8. An ADU is treated as new construction on the host parcel: the ADU itself receives a supplemental assessment at its construction-cost fair-market value as of completion date, while the primary dwelling's Prop 13 base-year value is NOT re-triggered. The supplemental assessment is prorated from the completion date through the end of the fiscal year and the annual assessment cycle thereafter. This 'addition only' treatment is the single most important ADU economic fact statewide: owners can add square footage via an ADU without resetting the Prop 13 base of the existing home. California Revenue & Taxation Code Section 74.3 further provides a New Construction Exclusion for ADUs used as the principal place of residence of a parent or child (intergenerational-housing ADU), but the exclusion is narrow and must be elected by timely filing.

Assessment policy: ADU new-construction supplemental assessments are issued after the building-permit final inspection, typically within 6 to 12 months of completion (the longer end is common during active-permit-year backlogs). The supplemental tax bill is issued by the Sacramento County Department of Finance (Tax Collection division) separately from the annual roll bill. For most owner-built 500-800 sqft ADUs in unincorporated Sacramento County, typical observed supplemental assessments range from $130,000 to $250,000 of new assessed value (reflecting current construction cost, not finished-home-sale comps), yielding a supplemental annual property-tax increase of approximately $1,300 to $2,700 at the combined ~1.00-1.10% effective rate (1% Prop 13 base plus local voter-approved debt service and Mello-Roos CFDs where applicable). Owners planning an intergenerational ADU should file the Rev. & Tax. Code 74.3 Claim for New Construction Exclusion (Parent/Child ADU) promptly after permit issuance; late filings lose benefit for prior fiscal years. The Sacramento County Assessor publishes an ADU-specific supplemental-assessment bulletin aligned with the Board of Equalization's statewide template.

Sacramento County administers or co-administers several overlay regimes that materially affect ADU siting on unincorporated parcels: (1) the Delta Primary Zone, established under the Delta Protection Act (Pub. Res. Code Division 19.5) and administered jointly by the Delta Protection Commission and Sacramento County, which constrains residential development on the roughly 500,000-acre agricultural core of the Sacramento-San Joaquin Delta; (2) FEMA Special Flood Hazard Areas (SFHA) along the Sacramento River, American River, Cosumnes River, Mokelumne River, Dry Creek, and Delta sloughs, with floodway and floodplain restrictions enforced jointly with the 50+ local Reclamation Districts that maintain levees across the Delta and Natomas Basin; (3) Very High Fire Hazard Severity Zones (VHFHSZ) designated by CAL FIRE covering the eastern foothill fringes approaching Folsom Lake and the Cosumnes River gorge toward El Dorado County; (4) Williamson Act agricultural preserve contract lands covering roughly 290,000 acres of unincorporated farmland, which restrict non-agricultural construction (including ADUs unless they support the contract's agricultural use); (5) Airport Land Use Compatibility Plans (ALUCP) administered by the Sacramento Area Council of Governments (SACOG) Airport Land Use Commission covering Sacramento International, Sacramento Executive, Mather Field, Rio Linda Airport, and Franklin Field; and (6) the Natomas Basin Habitat Conservation Plan (NBHCP), a federally-approved HCP covering roughly 53,000 acres of the Natomas Basin that imposes mitigation-fee and take-permit requirements on residential construction. Coastal Commission jurisdiction does not apply to Sacramento County (the county is not coastal). Seismic-retrofit overlays are not a county-administered regime in Sacramento County; California seismic building-code compliance applies statewide through the California Building Code adopted by the county.

• Delta Primary Zone — Delta Protection Commission / Sacramento County joint administration — ADUs on existing residential parcels inside the Primary Zone are permitted but reviewed for LURMP consistency. New residential parcels cannot be created in the Primary Zone and ADUs cannot be used to effectively subdivide agricultural land. Delta Protection Commission advisory review adds roughly 30-45 days to the overall ADU timeline, though the state ADU 60-day ministerial clock runs in parallel and cannot be extended beyond state limits.
• FEMA Special Flood Hazard Areas (SFHA) and Reclamation District levee-protected lands — ADUs in an SFHA require lowest-floor elevation to or above Base Flood Elevation plus one foot of county freeboard, flood vents on enclosures below BFE, structural anchoring, and a post-construction Elevation Certificate. In the Natomas Basin, the 2008-era FEMA de-accreditation of the levee system was resolved via the multi-billion-dollar Natomas Levee Improvement Program completed in stages through 2021, restoring A99 mapping; owners should verify current effective FIRM panel before design. Delta-island ADUs face case-by-case elevation requirements depending on the reclamation district's levee certification status and applicable FEMA panel.
• CAL FIRE Very High Fire Hazard Severity Zones (VHFHSZ) — foothill fringe — An ADU in a VHFHSZ must comply with California Building Code Chapter 7A (WUI-rated exterior materials: ignition-resistant siding, dual-pane windows, 1/8-inch-max vent screens, Class A roofing, non-combustible eaves / soffits / decks), minimum 100-foot defensible space per Pub. Res. Code Section 4291, minimum driveway width and turnaround per fire-district standards, and minimum fire-flow water supply (2,500 gpm residential standard, reduced for sprinklered ADUs per California Residential Code Section R313). The WUI premium on ADU construction cost in VHFHSZ areas runs an estimated 6-12% over comparable non-WUI construction.
• Williamson Act agricultural-preserve contract lands — An ADU on a Williamson Act parcel requires a county finding that the ADU is compatible with the contract's agricultural use. A non-farming rental ADU on a contract parcel is typically NOT compatible and may require contract non-renewal (a 9-year wind-down) before an ADU can be built for non-agricultural rental. Farm-employee ADUs and immediate-family ADUs are commonly found compatible. Owners should confirm Williamson Act status via the county parcel viewer before ADU design.
• Airport Land Use Compatibility Plans (ALUCP) — SACOG Airport Land Use Commission — An ADU in an ALUCP safety zone (Zones 1-6) may face density restrictions, avigation-easement recording requirements, and noise-attenuation construction standards (STC-rated windows, forced-air HVAC with acoustic treatment, soundproof attic insulation) for the 60/65/70 dB CNEL noise contours. Within the Mather Field AIA, the Board of Supervisors has historically applied the Mather ALUCP strictly; owners should verify AIA / safety-zone / noise-contour status on the SACOG ALUC maps before ADU design.
• Natomas Basin Habitat Conservation Plan (NBHCP) — An ADU in the Natomas Basin must pay the NBHCP mitigation fee in addition to the standard county fee package. The mitigation fee funds habitat acquisition and management protecting giant garter snake, Swainson's hawk, and other listed species. Owners should confirm in-basin status on the county parcel viewer and obtain a NBHCP fee quote from the Natomas Basin Conservancy before finalizing the ADU budget.