Rialto's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Rialto, California, there are 9 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.

Tiny Homes

Tiny homes in Rialto are regulated either as ADUs under California Government Code §65852.2 (state ADU law) and Rialto Municipal Code Title 18, or as RVs/manufactured housing under state HCD rules. Permanent tiny homes on foundations qualify as ADUs and benefit from California's ministerial-approval preemption.

Key details: Permanent tiny home: Processed as ADU per Cal. Gov. Code §65852.2. On wheels (THOW): RV under HCD Title 25 / Vehicle Code - not a dwelling unless ADU-certified. Building code: CRC Appendix Q for tiny houses under 400 sf. Local zoning: RMC Title 18 (must conform to state ADU law).

Living in an unpermitted tiny home, RV, or trailer as a permanent residence on a Rialto lot is enforced by Community Compliance under Title 8 (Health and Sanitation) and Title 18 (Zoning), with citations, abatement orders, and potential removal. ADU approvals improperly denied may be appealed to HCD under Gov. Code §65852.2(h).

ADU Rental Restrictions

Rialto cannot ban ADU rentals, but state law (Cal. Gov. Code §66314(a)(6)) prohibits renting an ADU for less than 30 days. Long-term rentals are permitted by right; short-term vacation rentals in ADUs are not allowed under state law statewide.

Key details: Min rental term: 30 days (Cal. Gov. Code §66314(a)(6)). Short-term rentals: Prohibited statewide for ADUs. Long-term rentals: Allowed; city cannot ban. AB 1482 rent cap: 5% + CPI, max 10% annually (Civil Code §1947.12) — exemptions apply. JADU rentals: Cannot be rented separately from owner-occupied main house (§66333).

Renting an ADU for under 30 days violates state law and can be cited as a zoning violation under RMC Title 18. AB 1482 violations (overcharging rent) can result in tenant lawsuits for damages plus attorney fees.

ADU Impact Fees

ADUs under 750 sq ft are exempt from all impact fees in Rialto by force of state law (Cal. Gov. Code §66314(f)(3)). ADUs 750 sq ft or larger may be charged impact fees only proportionally to the primary dwelling's square footage. School-district fees are separately governed.

Key details: Impact fee exemption: ADUs under 750 sq ft — zero impact fees (Cal. Gov. Code §66314(f)(3)(A)). Larger ADUs (750+ sq ft): Proportional fees only, based on ratio to primary dwelling. School fees: Not preempted; may apply over 500 sq ft (Ed. Code §17620). Building permit fees: Cost-of-service charges still apply. Enforcement: HCD complaint under Gov. Code §66317.7.

Charging impact fees on a sub-750-sq-ft ADU is a violation of state law; applicants can demand a refund under Gov. Code §66314 and may file a complaint with HCD. HCD has authority under Gov. Code §66317.7 to refer noncompliant ordinances to the Attorney General.

Rialto is more permissive than most cities when it comes to adu impact fees. That said, there are still limits.

ADU Permits

ADU permits are issued by the Rialto Building & Safety Division (150 S Palm Ave). State law (Gov. Code §66317) requires the city to act on a complete ADU application within 60 days, ministerially, with no discretionary hearing. Plans must comply with the California Building Standards Code (effective 2025 edition as of Jan. 1, 2026) and RMC Title 15.

Key details: Permit issuer: Rialto Building & Safety Division. Address: 150 S Palm Avenue, Rialto, CA 92376. Phone: (909) 820-2505. Statutory review window: 60 days (Cal. Gov. Code §66317(b)). Code edition: 2025 California Building Standards (effective Jan. 1, 2026).

Starting construction before permit issuance triggers stop-work orders and investigation fees (typically 2x permit fee) under the California Building Code §110 as adopted by RMC Title 15. Failure to call for required inspections can result in tear-out and re-inspection charges.

Garage Conversions

Rialto ministerially approves conversion of an existing, legally permitted garage into an ADU with no new setbacks and no replacement parking, but the garage door must be replaced with windows or doors matching the home. Unpermitted units built before 2020 can be legalized under AB 2533.

Key details: Approval: Ministerial; conversions keep existing setbacks. Garage door: Must be removed and replaced with matching windows/doors. Replacement parking: Not required when garage or carport is converted. Allowed expansion: Up to 150 sq ft for ingress and egress (Gov. Code 66323). Pre-2020 units: Legalization path under AB 2533 / Gov. Code 66332.

Unpermitted garage conversions are subject to code enforcement, but for units completed before January 1, 2020 the city may not penalize an applicant seeking legalization and must approve permits needed to correct health and safety violations.

ADU Owner Occupancy

Rialto cannot impose an owner-occupancy requirement on ADUs permitted between Jan. 1, 2020 and Jan. 1, 2025 (Cal. Gov. Code §66314(a)(6)). Owner-occupancy is required for Junior ADUs (JADUs) under Cal. Gov. Code §66333 — owner must live in either the main house or the JADU.

Key details: ADU owner-occupancy: Cannot be required for permits issued Jan 2020-Jan 2025 (Cal. Gov. Code §66314(a)(6)). JADU owner-occupancy: Required — owner must live in main house or JADU (Cal. Gov. Code §66333(a)). Deed restriction: Required for JADUs only — filed before final inspection. After Jan. 1, 2025: Cities may impose owner-occupancy on new ADU permits.

Falsely claiming owner-occupancy at JADU permit issuance is grounds for permit revocation and code-enforcement abatement under RMC Title 18. The recorded deed restriction is enforceable by the city against any future owner.

If you are coming from a city with tighter rules, you will find Rialto gives residents more flexibility on adu owner occupancy.

Shed Rules

Rialto lists accessory buildings and gazebos among work requiring a building permit. Under Municipal Code Section 18.52.030, detached accessory buildings may occupy at most 25 percent of the rear yard and need 10 feet of separation from the house if over 120 square feet.

Key details: Rear yard coverage: Max 25% of rear yard for detached accessory buildings. Total lot coverage: Max 30% of lot area in single-family zones. Setback: May be within 5 ft of interior property lines by the rear yard. Separation: 10 ft from main house if roof area exceeds 120 sq ft. Living quarters: Accessory buildings may not be used as living quarters.

Unpermitted accessory buildings are code violations; Rialto requires permits for accessory buildings, gazebos, patios, and masonry walls, and code enforcement can require after-the-fact permits or removal. Contact Building and Safety at (909) 820-2505.

ADU Rules

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.

Key details: 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.

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.

Carport Rules

Rialto's Building and Safety standard bars using a residential patio cover as a carport or garage, and R-1 zoning limits private garages to a three-automobile capacity with an 18-foot setback when a side-yard garage opens onto the street.

Key details: Patio cover height: Max 12 feet, one story, recreational use only. Prohibited use: Patio covers may not serve as carports, garages, or storage. Garage capacity: Private garages limited to 3 automobiles in R-1 zones. Side-yard garage setback: 18 ft from side property line when opening onto street. Patio cover setbacks: 5 ft from side lot line, 10 ft from rear lot line.

Using a patio cover as a carport or garage violates the city standard; non-standard covers and unpermitted carports can draw stop-work orders and after-the-fact permitting through Building and Safety, (909) 820-2505.

The Bottom Line

Compared to many U.S. cities, Rialto gives residents more room on accessory structures. 2 of the 9 rules here are rated permissive. But permissive does not mean unregulated. There are still requirements, and the city does enforce them when violations are reported.

All of the above reflects Rialto's municipal code as of our last review. If you need specifics on fines, exemptions, or filing requirements, the detailed ordinance pages linked above have the full breakdown.