An attached ADU is built as an addition to your existing home, on the side, at the back, or above an attached garage. It is a legally separate dwelling with its own front door, kitchen, bathroom and living space. A fire-rated wall separates it from your home.
When an attached ADU makes sense
- Tight lots where there is no room for a separate backyard home
- Corner lots with a long side yard
- Homes with an attached garage you want to keep, by building above it
- Families who want an aging parent close by with a shared wall instead of a walk across the yard
Size and design rules
- Up to 1,200 sq ft or 50% of the main house, whichever is less
- 4-foot side and rear setbacks
- Up to two stories and 25 feet under Oxnard’s ordinance standards
- Its own exterior entrance; an interior door to the main house is optional
- Roofline, siding and windows designed to match the existing home
Doing it right
An attached ADU changes your existing house, so good planning is critical:
- Structural engineering for the new foundation and how the roofs tie together
- Fire separation between units
- Sound insulation in the shared wall and floor
- Utilities: often a new electrical sub-panel and plumbing branch, sometimes separate meters
- Weatherproofing where new meets old, which is especially important with Oxnard’s salt air and winter storms
Attached ADU vs. a regular room addition
A room addition just makes your house bigger. An attached ADU creates a second legal home, which can be rented, adds more resale value and qualifies for the faster, ministerial ADU approval process. If you were planning an addition anyway, it is worth asking whether designing it as an ADU makes more sense.
Get a free consultation and a builder will look at your house, your lot and your goals.
Common questions
How big can an attached ADU be in Oxnard?
An attached ADU in Oxnard can be up to 1,200 sq ft or 50% of the floor area of the main house, whichever is less. State law still guarantees at least an 800 sq ft ADU where the lot can fit it.
Is an attached ADU cheaper than a detached one?
Sometimes. Sharing a wall and being close to existing utilities can save money, but tying into an existing roof and structure adds work. On a tight lot, an attached ADU may be the only way to fit the size you want.
Can an attached ADU be built as a second story?
Yes. An ADU can be built above an attached garage or as a second-story addition, subject to height limits and structural engineering. Oxnard allows ADUs up to two stories and 25 feet under its ordinance standards.