ADU rules in Unincorporated Ventura County
The key facts first, then what we've learned building there.
The snapshot
Checked October 2026. We re-check every lot against the current code.
Unincorporated Ventura County
| Rule | Answer |
|---|---|
| Detached ADU size | Up to 1,200 sq ft |
| Setbacks | 4 ft side and rear |
| Height | 16 ft; 18 ft near transit; 25 ft attached |
| Pre-approved plans | Yes, the county runs pre-reviewed standard ADU plans |
| Coastal and inland | Coastal areas have their own rules and may need a coastal permit |
| Fire zones | Much of the county is mapped fire hazard; ember-resistant construction applies |
| Rural lots | Septic and well review may apply on larger lots |
| Electricity | SCE |
| Building department | Ventura County Resource Management Agency (RMA) |
What's different here
The county offers pre-reviewed ADU plans, a faster path than a fully custom design.
Coastal areas follow coastal rules and may need a coastal permit; inland areas don't.
Large parts of the county are fire hazard zones, which bring ember-resistant materials and access checks.
On larger lots, septic, well and long utility runs shape where the ADU goes.
What applies here
Cities must now keep a set of pre-approved ADU plans.
Learn moreRebuild after a fire, with an ADU to live in or rent while the main house goes up.
Learn moreSB 9 lets a single-family lot be split in two, with up to two homes on each.
Learn moreSince January 2025, California lets an existing apartment property add detached ADUs, one for every existing unit up to eight, plus conversions of garages and storage.
Learn morePlans that fit
Ready-drawn plans we adapt to your lot and your city.
Ask about your address
We check the lot against these rules and tell you what fits.