Cities | Rialto
Rialto, California Multiplex Rules 2026: Zoning, ADUs, SB 9, Apartments, the Housing Opportunity District and Fees
Rialto, California is a city of 106,554 people in San Bernardino County. Its zoning and subdivision rules sit in Titles 18 and 17 of the Rialto Municipal Code, published on Municode. The ADU section dates from 2020 and the SB 9 chapters from 2022, and state law has changed since, so on several points the statute now decides. In 2026 the City Council adopted an updated Housing Element and a Housing Opportunity District that allows 35 to 50 homes per acre on 315 parcels. This page sums up the ways to build two, three, four or more homes on a Rialto lot. The seven guide pages below cover each topic in depth.
Rialto in six facts
- The US Census Bureau estimates the population of the City of Rialto, California at 106,554 on July 1, 2025. Source: US Census Bureau, Vintage 2025
- Rialto's zoning rules are Title 18 of its Municipal Code; the Municode copy, Supplement 39, is current through Ordinance No. 1713 of April 28, 2026. Source: RMC preface
- Apartments are allowed in R-3 at one home per 2,000 square feet of net lot area and in R-4 at one per 900 square feet. Source: RMC Secs. 18.22.030, 18.24.030
- Ordinance No. 1709, adopted April 14, 2026, created a Housing Opportunity District at 35 to 50 homes per acre; it is not yet in the Municode copy. Source: Ordinance No. 1709
- Rialto's ADU section dates from July 14, 2020, and state law now overrides it on height, unit counts and fees. Source: RMC Sec. 18.10.070; Gov. Code 66323
- SB 9 two-home projects and lot splits are allowed on single-family lots, approved by the Community Development Director with no hearing. Source: RMC Secs. 18.113.040, 17.51.040
Rialto Guide Pages
Start With State Law
Four state laws set the minimum Rialto 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 a house. SB 684 and SB 1123 allow maps of up to 10 lots with 10 homes. The state density bonus gives extra homes to projects of five or more units that include affordable homes.
Rialto writes ADU law into Section 18.10.070, SB 9 into Chapter 18.113 for two-home projects and Chapter 17.51 for lot splits, and the density bonus into Chapter 18.101. It has no section of its own for SB 684 and SB 1123 maps, so the statute applies directly. Where a Rialto section is stricter than the current statute, the statute controls; the guide pages name each such point.
SB 79 allows taller and denser projects near qualifying rail and bus stops. The state Department of Housing and Community Development (HCD) says in its SB 79 advisory that its upzoning took effect on July 1, 2026 in seven counties: Alameda, Los Angeles, Sacramento, San Francisco, San Mateo, Santa Clara and San Diego. San Bernardino County is not among them.
Rialto in Numbers
The US Census Bureau's Vintage 2025 city file estimates 106,554 people in the City of Rialto on July 1, 2025, up from a 2020 estimates base of 103,944. In that file Rialto is the 65th largest city in California, after Jurupa Valley (107,311) and ahead of West Covina (105,301). San Bernardino County has 2,224,091 people in the same file.
The code's preface says the Rialto Municipal Code was "originally published by Book Publishing Company in 1973" and that the current supplement "brings the Code up to date through Ord. No. 1713, passed April 28, 2026." Many zoning sections have history notes that cite the "1965 code." The City Council meets on the second and fourth Tuesday of each month, and its agendas are posted in the City's Legistar system.
The City's Housing Opportunity District page gives a state housing allocation of 8,272 homes for 2021 to 2029: 2,218 very low income, 1,206 low income, 1,371 moderate income and 3,477 above moderate income. The City Council adopted the updated Housing Element by Resolution No. 8474 on March 10, 2026. The three or more homes page covers what that plan commits the City to change.
The Ways to More Homes Compared
| Way | Where | Homes | Approval |
|---|---|---|---|
| ADU and junior ADU | Any single-family or multi-family residential zone | House plus a converted ADU, a detached ADU and a JADU (state law) | Staff, 60 days |
| SB 9 two-unit project | R-1 zones | 2 main homes of 500 to 800 sq ft each | Director, no hearing, no appeal |
| SB 9 urban lot split | R-1 lots of 2,400 sq ft or more | 2 lots of 40 to 60 percent, up to 2 homes each | Director, no hearing |
| Small multiplex | R-3 | Up to 4, at one per 2,000 sq ft of net lot area | Precise plan of design, Director |
| Apartments | R-3 (5 or more), R-4 | R-4: one per 900 sq ft of lot area | Planning Commission |
| Housing Opportunity District | 315 listed parcels | 20 to 50 per acre | By right with 20 percent lower-income homes |
| Small-lot map (SB 684 / SB 1123) | Multifamily lots up to 5 acres; vacant single-family lots up to 1.5 acres | Up to 10 | Staff approval with no hearing under Gov. Code 66499.41, 60 days |
Sources: Rialto Municipal Code Sec. 18.10.070, 18.113.050, 17.51.050, 18.22.040, 18.22.030 and 18.24.030 (Supplement 39); Ordinance No. 1709; Gov. Code 66323, 65852.21, 66411.7 and 66499.41.
Zones That Allow Homes
The house zones are A-1 (one-acre lots), R-1A and R-1B (8,400 square feet), R-1C (7,700), R-1A-10,000 and R-1D, a planned zone for tracts of ten acres or more. Each R-1 zone sets a minimum house size as well as a lot size. Title 18 has no R-2 chapter. Apartments are allowed in R-3 at one home per 2,000 square feet of net lot area and in R-4 at one per 900 square feet, with townhouses in the PRD-A zone at up to twelve per net acre. The City also lists nine specific plans with their own zones. See the zoning districts page.
House Lots: ADUs and SB 9
Section 18.10.070, added in July 2020, allows ADUs on every lot in a single-family or multi-family residential zone and requires a decision within sixty days with no hearing. It caps height at 16 feet or one story and allows one ADU and one junior ADU per house lot. State law now requires more: a converted ADU, a detached ADU of up to 800 square feet and a junior ADU on one lot, and 18 feet for a detached ADU near a major transit stop. The City lists 11 pre-selected ADU plans. See the ADUs and SB 9 page.
SB 9 allows two main homes on an R-1 lot under Chapter 18.113, each 500 to 800 square feet, or a split into two lots of 40 to 60 percent each under Chapter 17.51, starting from a lot of at least 2,400 square feet. The applicant for a split must sign an affidavit to live in one of the homes for three years. The lot size and subdivisions page covers lot splits, parcel maps and small-lot maps.
Three or More Homes
In R-3, four or fewer homes need a precise plan of design approved by the Community Development Director, and five or more need a conditional development permit from the Planning Commission. Projects in R-3 and in the Housing Opportunity District where at least 20 percent of the homes are for lower-income households are allowed by right. Ordinance No. 1709 sets the District's density at 35 or 40 homes per acre by area, 50 where the base zone is commercial, and at least 20 on every site. Rialto's own density bonus table stops at 35 percent, and the state bonus reaches 50 percent. See the three or more homes page.
Parking, Setbacks and Height
A house needs two spaces in an enclosed garage. An apartment needs two spaces, one of them in a garage, plus one guest space for every four homes, and tandem parking does not count. R-1 lots need a 25-foot front yard and may cover 30 percent of the lot. Heights run from 35 feet in R-1 and R-3 to 75 feet in R-4. See the parking, setbacks and height page.
Warehouses and Hazard Zones
Rialto amended its warehouse chapter in September 2025 to comply with state Assembly Bill 98. A new warehouse within 900 feet of a home or residentially zoned land must keep a buffer of 50 to 100 feet, and large ones must keep loading bays 300 to 500 feet away. The Rialto Fire Department told the City Council in June 2025 that the new state fire maps removed the very high fire hazard zone from the city and enlarged the high and moderate zones. Flood areas and earthquake fault zones have their own permit rules. See the warehouses and hazard zones page.
Fees
Rialto charges flat planning fees: its posted schedule lists $2,468.40 for a residential precise plan of design under five acres and $1,369.60 plus the City Clerk's cost for an appeal to the City Council. New homes pay development impact fees at final inspection. On the posted schedule, which shows fees effective July 1, 2021, the per-home lines add up to $20,449.05 for a single-family home and $15,105.17 for a multi-family home before water and school fees (VanPlex arithmetic), and the code raises the fees each July 1. See the permits and fees page.
Recent City Council Actions
- August 8, 2023. Ordinance Nos. 1681, 1682 and 1683 created the residential overlay and made projects with 20 percent lower-income homes a by-right use in R-3.
- May 14, 2024. Ordinance No. 1693 updated the floodplain chapter to the May 8, 2024 federal flood study.
- January 28 and February 25, 2025. Council agendas listed Urgency Ordinance Nos. 1697 and 1698, a moratorium on new indoor storage facilities and its extension.
- July 22, 2025. Ordinance No. 1700 adopted the state's updated fire hazard severity zone maps.
- September 23, 2025. Ordinance No. 1703 amended the warehouse chapter for Assembly Bill 98.
- March 10, 2026. Resolution No. 8474 adopted the updated 2021-2029 Housing Element.
- March 24, 2026. Ordinance Nos. 1710 and 1711 added the Housing Opportunity District to the Foothill Central and Gateway specific plans.
- April 14, 2026. Ordinance No. 1709 amended Chapter 18.116 to create the Housing Opportunity District. It is not printed in Supplement 39.
Where the Code, City Documents and State Law Differ
The guide pages flag each difference where it arises. The main ones:
- Supplement 39 prints the 2023 overlay at 50 homes per acre in five areas; Ordinance No. 1709 sets 35 or 40 by area and 50 where the base zone is commercial. The ordinance controls.
- Section 18.10.070 allows one ADU and one junior ADU per house lot and caps height at 16 feet or one story; Government Code 66323 and 66321 require more. The statutes control.
- Section 18.10.070 exempts ADUs "under seven hundred fifty square feet" from impact fees; Government Code 66311.5 exempts ADUs of 750 square feet or less.
- Chapters 18.113 and 17.51 set no decision deadline; Government Code 65852.21 and 66411.7 require a decision within 60 days or the application is deemed approved.
- Chapter 18.101 caps the density bonus at 35 percent; Government Code 65915 allows up to 50 percent.
- Section 18.68.040 gives fifteen days to appeal a Planning Commission decision; Section 18.66.090 makes a conditional development permit decision final after five days.
- The City's AB 98 page says Ordinance No. 1703 was adopted on September 9, 2025; the September 9 agenda lists its first reading, and the code's history note gives September 23, 2025.
- The impact fee schedule on the City's Fees page is dated July 1, 2021, while Section 3.33.040 raises the fees each July 1.
Limits of This Guide
The code comes from Municode's Supplement 39, current through April 28, 2026. Later City actions come from City Council, Planning Commission and Economic Development Committee agenda records in the City's Legistar system and pages on rialtoca.gov, read on October 10, 2026. Those records were searched through October 8, 2026 and showed no later ordinance on zoning, ADUs or SB 9. Final City Council minutes for 2025 and 2026 were not found in that system, so votes are given only where a signed ordinance or resolution was read. The zoning map, the General Plan, the nine specific plans and the Housing Opportunity District maps were not read in detail, and the City's current impact fee amounts after 2021 were not found. Whether Rialto is a general law or charter city was not confirmed from a City document. Ask the Planning Division at (909) 820-2535 which standards apply to your lot and whether any later ordinance applies.
Best For
- ✓ House lots that can take a converted ADU, a detached ADU and a JADU under state law.
- ✓ R-3 lots of 8,000 square feet or more, for four homes with only a precise plan of design.
- ✓ Housing Opportunity District sites, at 35 to 50 homes per acre.
Usually Fails When
- ✕ A plan follows a Rialto limit from 2020 or 2022 with no check of the current statute.
- ✕ An R-3 project of five or more market-rate homes is budgeted with no Planning Commission hearing.
- ✕ The fee budget uses the 2021 posted amounts with no check of current rates.
What To Verify Before Spending Money
- → The lot's zone, any specific plan and whether it is on the Housing Opportunity District list.
- → Current impact fees and planning fees with the City.
- → Flood, fault and fire hazard maps, and the zoning of neighboring land.
Where to Go Next
Related on VanPlex: the SB 684 and SB 1123 page, the California impact fees page and the duplex to fourplex guide.
Frequently Asked Questions
How many people live in Rialto, California?
Where is the Rialto zoning code?
What is the easiest way to add a home to a Rialto house lot?
Which state housing laws apply in Rialto?
When did Rialto last change its housing rules?
Does Rialto have a duplex zone?
How many parcels are in the Rialto Housing Opportunity District?
Who do I contact about zoning for a Rialto lot?
Are short-term rentals allowed in Rialto ADUs and SB 9 homes?
What should I check before buying a Rialto lot to add homes?
Official sources (checked October 2026)
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