Ventura County, CA Accessory Structures: ADU Rules (2026)
ADU rules in Ventura County, CA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Max ADU size (small lot)
- 850-1,000 sq ft
- Max ADU size (10+ acres)
- 1,800 sq ft
- Detached ADU height
- 16-18 ft, 2 stories max
- Side/rear setback
- 4 feet minimum
Summary
In unincorporated Ventura County, accessory dwelling unit floor area is capped by lot size, 850 to 1,800 square feet, under the county's ADU zoning standards, which also set height, story and setback limits for detached units.
g.ADU Size for Attached and Detached ADUs:(1)For lots that are nine thousand (9,000) square feet or less, the maximum total floor area of an attached or detached ADU shall be eight hundred fifty (850) square feet if there is one (1) bedroom or an efficiency unit; or one thousand (1,000) square feet if there is more than one (1) bedroom; or(2)For lots that are larger than nine thousand (9,000) square feet, but less than ten (10) acres, the maximum total floor area of an attached or detached ADU shall be one thousand two hundred (1,200) square feet; or(3)For lots that are ten (10) acres in size or larger, the maximum total floor area of an attached or detached ADU shall be one thousand eight hundred (1,800) square feet.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 51).
Full Breakdown
The zoning code sets maximum ADU floor area by lot size: 850 sq. ft. for a one-bedroom or efficiency unit (1,000 sq. ft. with more than one bedroom) on lots of 9,000 sq. ft. or less; 1,200 sq. ft. on larger lots up to 10 acres; and 1,800 sq. ft. on lots of 10 acres or more. Detached ADUs are capped at 16-18 feet in height and two stories, with 4-foot side and rear setbacks. This applies only in the unincorporated area, the ten incorporated cities, including Oxnard, Thousand Oaks and Ventura, apply their own ADU standards.
Violations & Fines
Building an ADU larger than the size cap for the lot, or exceeding height or setback limits, is a zoning violation subject to a Notice of Violation and administrative civil penalties under the county's enforcement provisions.
Frequently Asked Questions
How big can an ADU be on an unincorporated Ventura County lot?
Does this apply inside Oxnard or Thousand Oaks?
Sources & Official References
Other rules in Ventura County
How Ventura County compares: Easiest Cities to Build an ADU·California rules heatmap·Compare Ventura County to another location·View the California accessory structures overview
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