Arden

Sacramento County regulates ADUs on unincorporated parcels under its Zoning Code (Title 3, Chapter 5.4), adopted by the Board of Supervisors in 2020 and most recently updated in 2023 to conform with California's subsequent ADU preemption package. The county permits up to one ADU plus one JADU per single-family parcel ministerially, and the state-mandated two ADUs per multifamily lot; parking is not required within one-half mile of transit. The county ordinance layers the locally-controlled parameters (setbacks, design standards, objective height limits, fire-safe construction in WUI zones, Delta Primary Zone siting constraints, floodway restrictions) on top of California Government Code Sections 65852.2 (ADU) and 65852.22 (JADU), which preempt most local ADU regulation statewide. The county has adopted the state statutory framework of AB 68 / AB 881 (2019), SB 13 (2019 fee relief), AB 976 (2019 owner-occupancy removal through 2024, extended under subsequent amendments), AB 2221 / SB 897 (2022 design-review and permit-timeline clarifications), AB 1033 (2023 optional condo-separation — Sacramento County has NOT adopted an AB 1033 program as of 2026-04-20), AB 976-successor (permanent preemption of owner-occupancy rules), AB 2533 (2024 amnesty for unpermitted ADUs built before 2020), and SB 543 (2024 impact-fee clarifications). Distinct county-level contributions on top of the state floor are the Delta Primary Zone siting constraints administered jointly with the Delta Protection Commission, the Williamson Act contract-land provisions limiting ADU construction on parcels under active agricultural-preserve contracts, the Airport Land Use Compatibility Plan (ALUCP) review for ADUs within the Mather Field, Sacramento Executive, Sacramento International, and Franklin Field influence areas, and the Natomas Basin Habitat Conservation Plan (NBHCP) fees/review for ADUs constructed within the Natomas Basin.

• Sacramento County Zoning Code, Title 3 (Zoning), Chapter 5.4 (Accessory Dwelling Units)
• Sacramento County Planning & Environmental Review — ADU program webpage
• Board of Supervisors ordinance adopting the 2020 ADU conforming amendments (SCC Ord. 2020-0003 series)
• Board of Supervisors ordinance adopting the 2023 ADU update (SCC Zoning Code amendments for AB 2221 / SB 897 / AB 1033 conformance)

State-floor overlay: California state law (Gov. Code 65852.2, 65852.22) preempts most local ADU regulation. The state sets ministerial-approval requirements, caps fees, mandates 60-day permit review, forbids local owner-occupancy requirements (AB 976 and successor amendments making the removal permanent), sets minimum allowed sizes (850 sqft one-bedroom, 1,000 sqft two-bedroom), forbids parking requirements within one-half mile of transit or on replacement-covered-parking ADUs, and caps impact fees at zero for ADUs under 750 sqft. Sacramento County's ordinance reiterates and applies these floors, adding only the locally-controlled Delta, Williamson Act, airport, WUI, and floodplain overlays. Where a project sits in the Delta Primary Zone, a Williamson Act contract parcel, a Very High Fire Hazard Severity Zone, a FEMA Special Flood Hazard Area, or an Airport Influence Area, state ADU preemption still applies to the ADU allowance itself but does not preempt the county's separate authority over those overlay regimes.

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.

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)).