Riverside, CA Accessory Structures: ADU Rules (2026)
ADU rules in Riverside, CA, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.
Key Facts
- Detached ADU cap
- 1,200 sq ft maximum
- Attached ADU cap
- 50% of primary dwelling or 1,200 sq ft
- New one-story setback
- 4 ft side/rear if under 16 ft tall
- Height cap
- 20 ft single-story / 30 ft two-story
- Units per SFR lot
- Primary + 1 ADU + 1 JADU
Summary
Riverside's ADU rules set real numbers: a detached ADU can't exceed 1,200 square feet, new one-story ADUs under 16 feet need just a four-foot side/rear setback, height tops out at 20 feet for single-story units, and a single-family lot can host a primary home plus one ADU and one JADU, per §19.442.030.
D.Unit Size.1.Attached ADUs.a.The total floor area of an attached ADU, including conversion of existing floor area, shall not exceed 50 percent of the existing or proposed primary dwelling floor area or 1,200 square feet, whichever is less.b.The total floor area requirements shall not prevent the establishment of an ADU that is at least:i.850 square feet for units with one bedroom or less; orii.1,000 square feet for units with more than one bedroom .2.The total floor area of any detached ADU shall not exceed 1,200 square feet.3.The total floor area of any MADUs shall be between 150 square feet and 430 square feet as measured within the exterior faces of the exterior walls.4.JADUs shall be no more than 500 square feet in size. ... i.A minimum side and rear setback of four feet shall be provided for new one-story ADUs and MADUs under 16 feet in height. ... G.Height.2.Single-story detached ADUs and MADUs shall not exceed 20 feet in height.3.Two-story detached ADUs and ADUs constructed on the second floor of an existing accessory building, shall not exceed 30 feet in height.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 33).
Full Breakdown
030 sets the zoning standards for ADUs, MADUs, and JADUs in every residential zone. Unit size scales by type: an attached ADU is capped at 50 percent of the existing or proposed primary dwelling's floor area or 1,200 square feet, whichever is less, though the code guarantees at least 850 square feet for a one-bedroom unit and 1,000 square feet for anything larger; a detached ADU is capped at 1,200 square feet outright; MADUs run between 150 and 430 square feet; and JADUs can't exceed 500 square feet.
030(C)(2)(a)(i) requires only a four-foot side and rear setback for new one-story ADUs and MADUs under 16 feet tall, while taller new ADUs must meet the underlying zone's setback for the primary dwelling, and front and street-side setbacks always follow the underlying zone in full. 030(G), with the RC zone limited to a single story and 20 feet regardless. 030(E)(1)(a) allows the primary dwelling plus one attached or converted ADU, one detached new-construction ADU or MADU, and one JADU, up to four units total. There's no minimum lot size to qualify, and ADU floor area doesn't count toward the lot's overall coverage limit.
Violations & Fines
Exceeding the 1,200-square-foot detached cap, building past the four-foot setback minimum without the required zone setback for taller units, or adding more units than §19.442.030(E) allows on a single lot puts the project out of compliance with the chapter. Because ADU review is ministerial, the Community & Economic Development Director can deny or condition the permit for noncompliance rather than approving with a variance, and an as-built unit that doesn't match the approved plans is subject to standard code enforcement.
Frequently Asked Questions
How big can a detached ADU be in Riverside?
What setback does a new ADU need from my property line in Riverside?
How many ADUs can I build on one lot in Riverside?
Sources & Official References
Other rules in Riverside
How Riverside compares: Easiest Cities to Build an ADU·California rules heatmap·Compare Riverside to another location·View the California accessory structures overview
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ADU Rules in Nearby Cities
How other cities in Riverside County handle adu rules.