Can a manufactured home be an ADU in California?

Yes, a manufactured home can be an accessory dwelling unit in California. State ADU law expressly includes a manufactured home, as defined in Health and Safety Code section 18007, in its definition of an ADU, so a HUD-code home can serve as the second dwelling on a lot with an existing or proposed primary residence. For Central Valley homeowners with room in the back, this is one of the faster ways to add a real, permitted second home, because the home arrives largely built instead of framed from scratch on site.

Size limits to plan around

California caps detached ADUs at 1,200 square feet statewide, and cities cannot set a lower ceiling than that. Separately, the state protects ADUs of at least 800 square feet from objective local standards that would otherwise block them. Many manufactured floor plans fit comfortably inside these limits.

Foundation, utilities, and HCD

An ADU must provide complete independent living facilities: living, sleeping, eating, cooking, and sanitation. A manufactured home used as an ADU is connected to the required utilities and, in most cases, set on a permanent foundation and recorded on HCD Form 433A so it is treated as real property.

Faster permitting timelines

Recent changes to state ADU law tightened the clock on cities. A local agency typically must decide whether your application is complete within 15 business days, then approve or deny within 60 days of a complete application, and impact fees are generally prohibited on ADUs of 750 square feet or less. Rules still vary by city and county, so confirm setbacks and any local overlay with your jurisdiction. We help Fresno-area homeowners match a manufactured floor plan to their lot and the rules that apply to it.