Cities | Riverside

Riverside Multiplex Rules 2026: ADUs, SB 9, R-3 Zones and Hillside Limits

Riverside's rules for more than one home on a lot sit in the Riverside Municipal Code: Title 19 is the Zoning Code, Title 18 the Subdivision Code, Title 17 the Grading Code and Title 20 the Cultural Resources Code. This page sums up the routes to two, three, four or more homes on a Riverside lot, what each allows, and where City text and state law differ. Every code section was read in Supplement 33, which includes ordinances through No. 7776 of June 23, 2026. The seven guide pages below cover each topic in depth.

Riverside Guide Pages

Start With State Law

Four state laws set the floor Riverside must allow. SB 9 (2021) allows two main homes on a lot in a single-family zone, a split into two lots, or both, approved by staff with no hearing. ADU law sets the accessory dwelling units (ADUs), second homes on a lot, and junior ADUs a city must allow. A junior ADU is a unit of 500 square feet or less inside the walls of the house. SB 684 and SB 1123 allow maps of up to 10 lots with 10 homes. SB 79 raises zoning near qualifying rail and bus stops, but only in an "urban transit county," which Government Code 65912.156 defines as "a county with more than 15 passenger rail stations."

HCD's SB 79 advisory lists Alameda, Los Angeles, Sacramento, San Francisco, San Mateo, Santa Clara and San Diego Counties as the places where the upzoning took effect on July 1, 2026. Riverside County is outside that list. SB 9, ADU law and SB 684 all apply in Riverside today, and the City has written each into its own code: Chapter 19.442 for ADUs, Chapter 19.443 for SB 9 homes, Chapter 18.085 for SB 9 lot splits, and an SB 1123 checklist for small-lot maps.

Riverside is a charter city, a city that runs under its own local charter. Charter Section 200 gives it "the power to make and enforce all laws and regulations in respect to municipal affairs, subject only to such restrictions and limitations as may be provided in this Charter and in the Constitution of the State of California." The City states that Chapter 19.443 exists "to ensure compliance with California Government Code Sections 65852.21 and 66411.7, otherwise known as Senate Bill 9."

Riverside in Numbers

The US Census Bureau's Vintage 2025 city file estimates 323,057 people in the City of Riverside on July 1, 2025, up from a 2020 estimates base of 315,470. In that file Riverside is the twelfth largest city in California, after Bakersfield (422,165), Anaheim (341,008) and Stockton (324,597), and ahead of Irvine (318,764). Riverside County has 2,544,916 people in the same file.

The code that governs those residents' lots is organized by title. Chapter 19.100 holds the residential zones, Chapter 19.150 the use tables, Chapters 19.442 and 19.443 the ADU and SB 9 rules, Chapter 19.780 the Planned Residential Development permits, and Chapter 19.580 parking. Subdivision maps are in Title 18, hillside grading in Title 17, historic review in Title 20, and impact fees in Title 16.

The Routes to More Homes Compared

Sources: Riverside Municipal Code 19.442, 19.443, 18.085, 19.780, Tables 19.100.040 B and 19.150.020 A; City SB 1123 checklist.

House Lots: One Home Plus ADUs

Riverside's single-family zones are RA-5, RC, RR, RE and five R-1 zones, from R-1-1/2 Acre to R-1-7000. Table 19.100.040 A sets their density from 0.20 homes per gross acre in RA-5 to 6.2 in R-1-7000, and the smallest standard lot is 7,000 square feet. The use table prohibits apartments in all of them. So on a house lot, the routes to more homes come from state law.

The first is the ADU. Section 19.442.030 limits a house lot to "the primary dwelling; one attached or converted ADU; one detached, new construction ADU or MADU; and one JADU," which is four homes. A detached ADU may be 1,200 square feet and 20 feet tall on one story or 30 feet on two. No parking is required, and the floor area of an ADU is left out of lot coverage. Riverside also allows a movable ADU on wheels of 150 to 430 square feet.

Three City rules are stricter than the statute, and the statute controls in each case: zone setbacks for ADUs over 16 feet tall (state law caps side and rear setbacks at four feet), owner occupancy for every junior ADU (state law drops it when the junior ADU has its own bathroom), and impact fees on an ADU of exactly 750 square feet. See the ADUs and SB 9 page.

SB 9 in Riverside

Chapter 19.443 allows two main homes on a lot in "the R-1, RE, RR, RC, DSP-RES, and NSP-MDR single-family residential zones," considered "ministerially, without discretionary review or a hearing." An undivided lot may hold no more than four homes counting ADUs. Each SB 9 home needs one covered parking space unless the lot is near qualifying transit, side and rear setbacks are four feet, and the owner must live in one of the homes unless the lot came from a lot split.

Chapter 18.085 handles the SB 9 lot split. Each new lot must be at least 1,200 square feet and 40 percent of the original, the applicant signs a three-year owner occupancy affidavit, and the City Surveyor approves the map with no appeal. The City's checklist lists a filing fee of $5,240.58 for two parcels. SB 9 is barred on mapped arroyos, floodplains, habitat land, and in Historic Districts and Neighborhood Conservation Areas. The lots and subdivisions page covers the split in detail.

Three or More Homes

The R-3 and R-4 zones are where Riverside allows apartments outright. The five R-3 zones allow 10.9, 14.5, 17.4, 21.8 and 29 homes per gross acre, and R-4 allows 40, under Table 19.100.040 B. Every R-3 zone lists a 30,000 square foot minimum lot for new lots, but Section 19.100.075 sets lighter rules for existing lots under 21,780 square feet: five-foot interior side yards, a 40-foot height (45 feet over tuck-under parking), and no open space requirement for six or fewer homes. New R-3 and R-4 buildings need design review.

In single-family zones, a Planned Residential Development (PRD) can raise density with attached or detached homes: to 7.3 homes per gross acre in R-1-7000, or 8.0 with a design bonus. In R-3, a Small Lot PRD builds 16 or fewer houses on lots of 5,499 square feet or less. PRDs need a two-thirds vote of the Planning Commission. The density bonus in Chapter 19.545 adds 20 to 50 percent for projects with affordable homes. The three or more homes page covers each route.

R-3 and R-4 also permit tiny home communities on foundations, where buildings may sit five feet apart, and the MU-V and MU-U mixed-use zones allow 30 and 40 homes per acre, or 40 and 60 within half a mile of a transit stop on Magnolia or University Avenue. Along University Avenue, the City's 2026 density transfer pilot lets parcels move unused home counts to other parcels in the specific plan area.

Hillsides, Arroyos and Historic Districts

Riverside voters approved Proposition R and Measure C to protect hillsides, arroyos and farmland; the General Plan says Measure C passed in 1987. The City carries them out through the RC zone, where lots must be one-half acre under 15 percent average slope, two acres at 15 to 30 percent and five acres above 30 percent, and homes are limited to 20 feet and one story. The Grading Code bars "development or grading of any kind" within 50 feet of six named arroyos.

Title 20 governs historic property. Any change to a designated property or any building in a Historic District needs a Certificate of Appropriateness, and SB 9 is barred in Historic Districts and Neighborhood Conservation Areas. ADUs on historic lots follow design standards adopted February 19, 2025. See the hillsides and historic districts page.

Setbacks, Parking and Fees

An R-1-7000 house has a 20-foot front setback, 7.5-foot interior side yards and a 25-foot rear setback, with a 35-foot, two-story height limit. A house on an R-1 lot of 5,500 square feet or more needs two garage spaces, and apartments need 1.5 or 2 spaces per home, with 75 percent covered. State law bars minimum parking within half a mile of a major transit stop unless the City makes findings. The parking, setbacks and height page has the full tables.

The City's Planning Services Fee Schedule, "Effective July 1, 2026, by Resolution 24253," lists $11,849 for a tentative parcel map, $19,804 for a PRD and $8,552 for multi-family design review. Impact fees for parks, trails, fire stations, traffic and habitat are set in Title 16, with amounts set by City Council resolution, and ADUs under 750 square feet pay none. See the permits and fees page.

Where to Go Next

Related on VanPlex: the California impact fees page and the duplex to fourplex guide.

Frequently Asked Questions

Official sources (checked October 2026)