How Riverside Handles Accessory Structures: A Practical Guide

Riverside maintains 243 local ordinances across all categories, and 9 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where Riverside falls on the strict-to-permissive spectrum compared to other cities.

Tiny Homes

Riverside allows movable accessory dwelling units (MADUs) between 150 and 430 square feet on single-family lots under RMC Chapter 19.442. Tiny homes on wheels classified as RVs cannot be used as permanent dwellings on residential lots.

Key details: MADU size range: 150-430 sq ft. Detached ADU max: 1,200 sq ft. JADU max: 500 sq ft. THOWs as permanent dwellings: Not allowed on residential lots. Code chapter: RMC Chapter 19.442.

Occupying a tiny home on wheels as a permanent dwelling on a residential lot is a code violation enforced by Code Enforcement under RMC Title 1. Administrative citations follow the §1.17 escalating schedule (typically $100/$200/$500). The City may also pursue abatement to require removal of the THOW. Unpermitted MADUs without water, sewer, and electrical hookups face similar enforcement.

ADU Impact Fees

Per California Government Code §66323 (as amended by SB 543, 2025), Riverside may not charge any development impact, capacity, or connection fee on an ADU of 750 sq ft or less. For ADUs larger than 750 sq ft, the city's impact fees must be charged proportionately to the size of the primary dwelling.

Key details: Impact fees ADU ≤750 sq ft: $0 (exempt). Impact fees ADU >750 sq ft: Proportional to primary dwelling. JADU ≤500 sq ft: Exempt from impact fees. Plan-check fees: Still apply. Statutory authority: Gov. Code §66323.

A homeowner charged an impact fee in violation of Gov. Code §66323 may demand a refund and, after exhausting administrative remedies under Gov. Code §66020, sue to recover the unlawfully collected fee with interest. The city is required to refund fees collected in error.

If you are coming from a city with tighter rules, you will find Riverside gives residents more flexibility on adu impact fees.

ADU Owner Occupancy

Riverside does not impose an owner-occupancy requirement on standalone ADUs — this is preempted by California Government Code §66315. However, properties with a Junior ADU (JADU) under RMC §19.442 must have the owner occupy either the primary dwelling or the JADU per Gov. Code §66333.

Key details: ADU owner-occupancy: Not required (preempted). JADU owner-occupancy: Required. JADU deed restriction: Required (Gov. Code §66333). Separate sale of JADU/ADU: Prohibited.

For JADUs only: failure to maintain owner occupancy or record the required deed restriction is a violation of RMC §19.442.030 and Gov. Code §66333. Enforcement is via administrative citation under RMC §1.17 (up to $1,000/day under Gov. Code §36900(c)) and revocation of the JADU permit. For standalone ADUs, owner-occupancy cannot be enforced.

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

ADU Permits

An ADU in Riverside requires a building permit issued ministerially (no discretionary review) and must be approved or denied within 60 days of a complete application, per California Government Code §66317 and RMC Chapter 19.442.

Key details: Permit type: Ministerial building permit. Review timeline: 60 days (Gov. Code §66317). Issuing department: Riverside CEDD. Discretionary review: Not permitted. JADU deed restriction: Required (Gov. Code §66333).

Constructing or occupying an ADU without a permit triggers a stop-work order from the Building Official under California Building Code §114 and RMC §16.04. Civil penalties under RMC §1.17 begin at $100 and escalate; the property owner is also required either to obtain a retroactive permit (with double plan-check fees per the City's adopted Fee Schedule) or remove the structure.

Shed Rules

One-story detached storage sheds 120 sq ft or smaller are exempt from a building permit under California Residential Code R105.2 and Riverside Municipal Code Title 16, but they must still meet zoning setbacks in RMC Chapter 19.440 (Accessory Buildings and Structures).

Key details: Permit threshold: Over 120 sq ft, or any utilities. Max height (exempt sheds): One story. Zoning chapter: RMC Chapter 19.440. Habitation: Not allowed in an accessory shed. Permit issuer: Building & Safety Division (951-826-5697).

Building a shed without a required permit, or in violation of zoning setbacks, is a municipal code violation enforced by Code Enforcement under RMC Title 1 (administrative citations). Riverside's administrative citation fines under RMC §1.17 are typically $100 for the first violation, $200 for the second within a year, and $500 for each subsequent violation, plus the cost of bringing the structure into compliance or removing it.

ADU Rules

Riverside Municipal Code Chapter 19.442 governs Accessory Dwelling Units (ADUs), Junior ADUs (JADUs) and Movable ADUs (MADUs). Every single-family and multi-family property in the city is eligible for at least one ADU and one JADU under state law and §19.442.030.

Key details: Code chapter: RMC Chapter 19.442. Max detached ADU size: 1,200 sq ft. Max JADU size: 500 sq ft. Side/rear setback (≤16 ft tall): 4 feet. Minimum lot size: None.

ADUs built or occupied without a permit are subject to Riverside Municipal Code Title 1 enforcement: administrative citations starting at $100 (first), $200 (second), and $500 (subsequent) per RMC §1.17, plus stop-work orders and an order to demolish or legalize the unauthorized structure issued by the Building Official.

Carport Rules

Carports in Riverside are accessory structures under RMC Chapter 19.440 and must be permitted by Building & Safety. They must be open on at least two sides or they are reclassified as garages, and must meet zoning setbacks for their underlying residential zone.

Key details: Code chapters: RMC 19.440 & 19.580. Open sides required: At least 2. Permit required: Yes (Building & Safety). Historic district review: May be required. Fire-zone material rule: Ignition-resistant in VHFHSZ.

Building a carport without a permit is a code violation. Code Enforcement issues administrative citations under RMC §1.17 (typically $100 first offense, $200 second within 12 months, $500 third and subsequent). Unpermitted carports must either be removed or brought into compliance with after-the-fact permitting, which can include engineer-stamped plans.

ADU Rental Restrictions

Under RMC §19.442.030, ADUs, JADUs and MADUs in Riverside may only be rented for terms longer than 30 days — short-term vacation rentals are prohibited. This mirrors the local-agency authority granted by California Government Code §66314(a)(6).

Key details: Minimum rental term: 31 days. STR allowed in ADU: No. Authority: RMC §19.442.030; Gov. Code §66314(a)(6). Daily fine ceiling: Up to $1,000/day (Gov. Code §36900(c)).

Operating an ADU as a short-term rental violates RMC §19.442.030 and is subject to administrative citations under RMC §1.17: $100 first offense, $500 second, and $1,000 per day for continued violations involving building/zoning code under Gov. Code §36900(c). The city may also seek injunctive relief and recover enforcement costs.

This is one of the stricter rules in Riverside's municipal code. If you are unsure whether your situation complies, it is worth checking with the city before proceeding.

Garage Conversions

Converting an existing garage into an ADU or Junior ADU is permitted ministerially in Riverside under RMC Chapter 19.442 and California Government Code §65852.2. No replacement covered parking is required when the garage becomes an ADU.

Key details: Code chapter: RMC Chapter 19.442. State law: Cal. Gov. Code §65852.2. Replacement parking: None required. JADU size cap: 500 sq ft. Min rental term: 31+ days (no short-term).

Converting a garage to living space without a permit is a code violation enforced by Code Enforcement under RMC Title 1 administrative citations (typically $100/$200/$500 escalating). Unpermitted conversions can be ordered restored to the original garage or legalized via after-the-fact permits, which require full inspection and possible structural retrofits. Renting an unpermitted ADU adds further violations.

The rules around garage conversions in Riverside lean permissive, but that does not mean anything goes.

The Bottom Line

Compared to many U.S. cities, Riverside gives residents more room on accessory structures. 3 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 Riverside'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.