Permitting In Unincorporated Ventura County.
ADUs are allowed in every residential zone of unincorporated Ventura County, with state law driving much of the framework. The county reviews applications within 60 days of submittal, and most projects take three to four months to permit. The county's Resource Management Agency ADU page is the official reference.
Note that these rules cover unincorporated areas only. Incorporated cities like Ventura and Oxnard set their own requirements, so the first step is confirming your jurisdiction. Check your lot and we will do it for you.
Size Limits That Scale With Your Lot.
There is no minimum lot size for an ADU here, but how big you can build depends on your parcel and bedroom count. The base maximums are 850 square feet for studios and one-bedrooms and 1,000 square feet for two or more bedrooms. Lots over 9,000 square feet allow 1,200 square feet, and parcels over 10 acres allow detached ADUs up to 1,800 square feet. Attached ADUs follow the same tiers.
Height is capped at 16 feet, or 18 feet near transit or where the lot has a multi-story building. Set the unit back at least 20 feet from all property lines and it can match the primary home's height up to the zone's standard limit, with an extra 2 feet allowed to match the main house's roof pitch. JADUs must fit within the existing walls of the main home and top out at 500 square feet.
Setbacks, Special Areas, And Parking.
All ADUs need at least 4-foot side and rear setbacks. Two mapped areas carry extra limits: in the Ojai Traffic Impact Area, ADUs require parcels of at least 1 acre and are capped around 700 square feet, and in the Arroyo Santa Rosa/Tierra Rejada Groundwater Impact Area, allowable size runs roughly 700 to 1,200 square feet depending on lot size. The groundwater-area rules trace back to a county ordinance for the Santa Rosa Valley.
Parking is one off-street space for a new ADU, or two if it has two or more bedrooms (never more than two). The requirement is waived near transit, in historic districts, in permit-only parking zones where permits are not offered to the ADU, or near a car-share vehicle. Conversion ADUs and JADUs need no parking at all.
Eligibility And Unit Counts.
Any lot zoned for residential or mixed use in unincorporated Ventura County qualifies: standard single-family zones like R1, rural residential and agricultural zones, and multifamily zones. The one hard rule is that the ADU must share its parcel with an existing or proposed primary dwelling; a vacant lot cannot host an ADU on its own.
Single-family lots can add one ADU (attached or detached) plus one JADU, two extra units alongside the main home. Multifamily lots can add up to eight new detached ADUs plus interior conversions of non-livable areas like storage rooms or garages, up to 25% of the existing unit count. For projects at that scale, see Abodu's multifamily program. Owners should also review the County Assessor's ADU information to understand how a new unit is assessed.
What It Actually Costs.
Custom site-built ADUs in California routinely exceed $250,000 before the first change order lands.
Abodu quotes transparent published pricing: homes from $234,800 plus a published installation price, an expected all-in from $298,800, covering design, permits, the factory build, delivery, and installation. Here is how the process works, step by step.