ADU Rules: Fontana vs Ontario
How do adu rules rules compare between Fontana, CA and Ontario, CA?
Fontana has fewer restrictions than Ontario.
Fontana, CA
San Bernardino County
Fontana permits ADUs and JADUs under California Gov Code 65852.2. Ministerial approval within 60 days, no replacement parking for garage conversions, and detached ADUs up to 1,200 sq ft.
View full Fontana rules →Ontario, CA
San Bernardino County
Ontario must allow ADUs and JADUs under California Gov Code 65852.2 and 65852.22 on all single-family and most multifamily lots. Approval is ministerial within 60 days, with no minimum lot size.
View full Ontario rules →Key Facts Comparison
| Fact | Fontana | Ontario |
|---|---|---|
| Approval timeline | 60 days ministerial per GC 65852.2 | - |
| Max detached ADU | 1,200 sq ft or 1,000 sq ft by bedroom count | - |
| Parking rule | No added parking, no replacement for converted garage | - |
| Setbacks | 4 feet side and rear for new detached ADU | 4 ft side and rear |
| Impact fees | Waived for ADUs under 750 sq ft | - |
| State law | - | Gov Code 65852.2 and 65852.22 |
| Size | - | Up to 850-1,000+ sq ft detached |
| Parking | - | Waived near transit, half mile |
| Approval | - | Ministerial, 60 days |
Highlighted rows indicate differences between cities.
Fontana FAQ
Can I build an ADU on my Fontana single-family lot?
Yes. State law and Fontana Municipal Code allow one ADU plus one JADU on every single-family lot, subject to size, setback, and height limits.
Do I lose my garage parking if I convert it to an ADU?
You can convert the garage without providing replacement parking under state ADU law - the city cannot require a new covered space.
How long does ADU approval take in Fontana?
Complete applications must receive a ministerial decision within 60 days under Government Code 65852.2.
Ontario FAQ
Can Ontario deny my ADU application?
Only if the project fails the objective state-law or local standards. Otherwise state law requires ministerial approval within 60 days of a complete application.
Do I have to live on site to build an ADU?
No. State law suspends owner-occupancy requirements for ADUs permitted through January 1, 2025, a window that has been extended further by subsequent legislation.
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