A detached ADU, sometimes called a backyard home, guest house or casita, is a stand-alone house built behind or beside your main home. It has its own foundation, roof, entrance, kitchen and bathroom, and it is permitted as a legal second dwelling on your property.
In Oxnard, detached ADUs are the most popular choice for homeowners who want rental income or a private home for family. Tenants pay more for a unit with its own walls and entry, and parents or grown kids get real independence while living a few steps away.
What you can build in Oxnard
- Size: up to 850 sq ft for a studio or one-bedroom, up to 1,200 sq ft for two or more bedrooms
- Setbacks: 4 feet from side and rear property lines
- Height: 16 feet on most lots under the state standards, more near major transit; up to two stories under Oxnard’s ordinance when the ADU meets the city’s standards
- Parking: none required if you are within half a mile of public transit, and never for the parking you give up
- Approval: ministerial, with no public hearing; the city must decide within 60 days of a complete application, or 30 days with a pre-approved plan
See our Oxnard ADU rules guide for the full list, including the Coastal Zone.
Popular detached ADU layouts
| Layout | Typical size | Best for |
|---|---|---|
| Studio | 350–500 sq ft | Single tenant, home office, aging parent |
| One-bedroom | 500–750 sq ft | The rental sweet spot; stays under the 750 sq ft impact fee threshold |
| Two-bedroom | 750–1,000 sq ft | Families, roommates, highest rent |
| Two-bedroom, two-bath | 1,000–1,200 sq ft | Multigenerational living, long-term value |
Keeping a detached ADU at 750 sq ft or less means no city impact fees, which is why so many Oxnard one-bedrooms are designed right at that size.
What a full detached ADU project includes
- Site visit and feasibility. Lot size, setbacks, easements, the sewer lateral, the electrical panel and access for equipment.
- Design. Floor plan, elevations and finishes that match your main house, whether that is a 1960s ranch in Bryce Canyon or a newer two-story in Riverpark.
- Engineering and Title 24. Structural calculations, energy compliance and, for most new ADUs, rooftop solar.
- Permits. Oxnard ADU Zone Clearance through Planning, then plan check with Building & Engineering.
- Construction. Foundation, framing, roofing, plumbing, electrical, HVAC, insulation, drywall, cabinets, tile and finishes.
- Inspections and final. City inspections at each stage and final sign-off so the unit can be legally occupied.
Built for the Oxnard climate
Oxnard’s mild coastal weather is easy on people and hard on buildings. Salt air, fog and the marine layer mean corrosion-resistant fasteners, good flashing and moisture-smart wall assemblies matter more here than inland. Fiber cement or stucco siding, vinyl or fiberglass windows and a well-ventilated roof keep a backyard ADU looking new for decades.
What a detached ADU costs
Detached ADUs are the biggest ADU investment. In Oxnard most land somewhere around $220,000 to $400,000 or more, depending on size, foundation, utility runs and finishes. Our Oxnard ADU cost guide breaks down where the money goes.
Ready to see what fits your backyard? Call or request a free on-site consultation and a builder will walk the lot with you.
Common questions
How big can a detached ADU be in Oxnard?
Oxnard allows a detached ADU of up to 850 sq ft with one bedroom or less, and up to 1,200 sq ft with more than one bedroom. State law also guarantees you can build at least an 800 sq ft ADU with 4-foot side and rear setbacks, even on lots where other zoning rules would otherwise get in the way.
How tall can a detached ADU be?
A detached ADU built under the state's guaranteed standards can be 16 feet tall on most single-family lots, and 18 feet within half a mile of major transit, with 2 more feet allowed to match the main house's roof pitch. Oxnard's ordinance also allows up to two stories and 25 feet for ADUs that meet its other standards. Your builder will confirm which limit applies to your lot.
Does a detached ADU need its own utility meters?
Not necessarily. Many detached ADUs share the main house's water and gas service and run a new electrical sub-panel. Separate meters cost more but make it easier to bill a tenant. Your builder will look at your existing panel, sewer line and water service during the site visit.
Can I build a detached ADU and a junior ADU on the same lot?
Yes. On a single-family lot in Oxnard you can generally build one detached ADU plus one junior ADU inside the main house, for a total of three homes on the lot.