ADU Rules: Fontana vs Rialto
How do adu rules rules compare between Fontana, CA and Rialto, CA?
Fontana and Rialto have similar restriction levels.
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 →Rialto, CA
San Bernardino County
Rialto allows ADUs on single-family and multifamily lots under California Government Code §66314 (formerly §65852.2), with local zoning standards in Rialto Municipal Code Title 18 (Zoning). State law preempts most restrictive local provisions: a detached ADU up to 1,200 sq ft and a JADU up to 500 sq ft are allowed by right on a single-family lot, plus the city must permit at least one ADU and one JADU per single-family parcel.
View full Rialto rules →Key Facts Comparison
| Fact | Fontana | Rialto |
|---|---|---|
| Approval timeline | 60 days ministerial per GC 65852.2 | 60 days ministerial review (Gov. Code §66317) |
| 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 | - |
| Impact fees | Waived for ADUs under 750 sq ft | - |
| Governing law | - | Cal. Gov. Code §66314 (state ADU statute) + Rialto Municipal Code Title 18 (Zoning) |
| Max ADU size (state floor) | - | 850 sq ft studio/1-BR; 1,000 sq ft 2+ BR; up to 1,200 sq ft allowed |
| Min setback | - | 4 ft side/rear (state preemption) |
| Permit office | - | Rialto Building & Safety, 150 S Palm Ave, (909) 820-2505 |
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.
Rialto FAQ
Can Rialto deny my ADU if I meet state standards?
No. State law requires ministerial (non-discretionary) approval if your ADU meets the objective standards in Gov. Code §66314 — Rialto cannot impose a public hearing or design review on a code-compliant ADU.
Do I need to live on the property to build an ADU?
No owner-occupancy is required for an ADU permitted between Jan 1, 2020 and Jan 1, 2025 under Gov. Code §66314(a)(6). JADUs always require owner-occupancy of either the main house or the JADU under Gov. Code §66333.
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