Rialto, CA Accessory Structures: ADU Rules (2026)
ADU rules in Rialto, CA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Max ADU size
- 1,200 sq ft (50% of primary or 850-1,000 sq ft floor)
- Detached height limit
- 16 feet or one story, whichever is less
- Setbacks
- 4 ft minimum to side and rear property lines
- Review
- Ministerial, no hearing, 60-day decision
- Pre-approved plans
- 11 city pre-selected ADU plans, 499-1,200 sq ft
- Utilities
- Separate gas, water, and electric meters for detached ADUs
Summary
Rialto allows one ADU plus one junior ADU per single-family lot with ministerial approval within 60 days under Rialto Municipal Code Section 18.10.070. Detached ADUs are limited to 16 feet in height, four-foot side and rear setbacks, and 1,200 square feet maximum.
An ADU is a secondary housing unit that is built on the same lot as the primary residence. ... Development standards for ADUs, including height limits, size limits, lot coverage, and design guidelines can be located in the Rialto Municipal Code, Section 18.10.070. ... All detached accessory dwelling units require separate gas, water, and electric meters. All new detached dwellings require solar panels. New dwellings must match the architectural features of the primary dwelling and conform to the design standards. ... Setbacks less than 5 feet from the property line will require fire rated walls if the ADU is not sprinklered. Setbacks between dwellings must be 10 feet if the ADU is not sprinklered.
Full Breakdown
Rialto Municipal Code Section 18.10.070 caps ADU size at 50 percent of the primary dwelling or 850 square feet (1,000 square feet for multi-bedroom units), whichever is more, never exceeding 1,200 square feet. Height is limited to 16 feet or one story; side and rear setbacks are four feet. One parking space is required unless the unit is within one-half mile walking distance of public transit or converted from existing space. The city's ADU program page adds that detached ADUs need separate gas, water, and electric meters, all new detached dwellings require solar panels, and designs must match the primary dwelling. Eleven pre-approved plans (499 to 1,200 square feet) are available. State law (Government Code Section 66323) mandates ministerial approval.
Violations & Fines
Building an ADU without permits triggers code enforcement and after-the-fact permitting; however, under AB 2533 (Government Code 66332) Rialto cannot deny a permit to legalize a unit built before January 1, 2020 unless substandard conditions exist.
Frequently Asked Questions
Do I need a public hearing to build an ADU in Rialto?
Does Rialto offer pre-approved ADU plans?
Will my Rialto ADU need fire sprinklers?
Sources & Official References
Other rules in Rialto
How Rialto compares: Easiest Cities to Build an ADU·California rules heatmap·Compare Rialto to another location·View the California accessory structures overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.
ADU Rules in Nearby Cities
How other cities in San Bernardino County handle adu rules.