VANPLEX
David Babakaiff
Written by David Babakaiff · Co-Founder, VanPlex | 25+ Years BC Construction Last reviewed: October 2026

Ontario | Three or more homes

Ontario, California Three or More Homes: Multiple-Family Zones, Development Plans, Objective Design Standards, Density Bonus, Mixed Use and SB 79

This page covers projects of three or more homes on a lot in the City of Ontario: triplexes, fourplexes, townhomes and apartments. The Development Code has no section named for missing middle housing. The rules are the multiple-family standards of the Development Code, a Development Plan review that starts at three homes on a lot, and a set of objective design standards adopted in 2025. The state density bonus adds homes beyond the zone maximum. The Ontario overview has the summary.

Three or more homes in Ontario in six facts

Where Multiple-Family Homes Are Allowed

Table 5.02-1, the Land Use Matrix, marks multiple-family dwellings P, permitted, in the MDR-11, MDR-18, MDR-25 and HDR-45 columns and prohibited in AR-2, RE-2, RE-4 and LDR-5. The code defines the use as "Two or more attached dwelling units," so a duplex, a triplex, a row of townhomes and an apartment building are one use with one set of standards. The matrix also permits it in ten of the eleven mixed-use columns. In the CN and CC commercial zones homes come only as part of a residential mixed-use development with a Conditional Use Permit.

The number of homes comes from the density range of the zone, counted on the lot's area. The zoning districts page explains the range, the rounding and the minimum. For three or more homes the minimum matters as much as the maximum: a 10,000 square foot lot yields two homes in MDR-11, three or four in MDR-18 and five in MDR-25 (VanPlex arithmetic: 0.2296 acres times 11.0 is 2.5; times 11.1 and 18.0 is 2.55 and 4.13; times 18.1 and 25.0 is 4.16 and 5.74, with the minimum rounded up and the maximum rounded down).

Multiple-Family Standards by Zone

Standard MDR-11 MDR-18 MDR-25 HDR-45
Density range, homes per acre 5.1 to 11.0 11.1 to 18.0 18.1 to 25.0 25.1 to 45.0
Minimum project area 0.23 acre (10,000 sq ft) 0.23 acre (10,000 sq ft) 0.23 acre (10,000 sq ft) 1.0 acre
Minimum project width and depth 100 ft by 100 ft 100 ft by 100 ft 100 ft by 100 ft 180 ft by 200 ft
Maximum project coverage 60% 60% 60% 100%
Setback from public streets 20 ft freeway, 30 ft arterial, 20 ft collector or local Same Same 10 ft
Setback from interior project boundary 5 ft 5 ft 5 ft 5 ft
Maximum building height 35 ft 45 ft 60 ft 75 ft
Open space per home 500 sq ft 500 sq ft 400 sq ft 310 sq ft

Source: Ontario Development Code, Section 6.01.010, Table 6.01-3 and Table 6.01-4 (Rev. 08.18.2026). The open space row applies to projects of more than 3 dwellings.

  • Project area, in place of lot size. The table prints "N/A" for minimum lot size and lot coverage. It sets a minimum project area and a maximum project coverage. An existing lot below the project area "shall be permitted all of the development rights of the zone in which it is located, except that the maximum density shall be limited to the minimum number of dwelling units allowed within the specified density range."
  • Space between buildings. Detached buildings of up to two stories need 25 feet front to front and 10 feet side to side. Buildings of three stories or more need 30 feet and 15 feet. Rear to rear is 20 feet.
  • Drives and parking. Living area sits at least 15 feet from the edge of a private drive and 10 feet from parking spaces. Garages need 5 feet.
  • Storage. Each home needs 240 cubic feet of "lockable private storage space" in a garage, a storage building or a space reached from the home.
  • Near a freeway. "A health risk assessment shall be required for multiple-family development projects located within close proximity to a freeway, as determined by the Zoning Administrator."
  • Walls. Section 6.02.020 requires 6-foot walls or decorative fences on the interior side and rear project boundaries, and a 6-foot decorative masonry wall where the project meets neighboring residential development.
  • Trash. Projects without individual pickup provide trash enclosures at least 10 feet from the interior project boundary and from the livable part of any building.

Open Space and Recreation

Section 6.01.010.E applies to multiple-family projects "of more than 3 dwellings," so a triplex is below it and a fourplex is inside it. Table 6.01-4 sets open space for each home: 200 square feet private and 300 common in MDR-11 and MDR-18, 150 and 250 in MDR-25, and 60 and 250 in HDR-45. The split is "recommended and may be adjusted by the developer," and the total must be met.

  • Private open space. At the home's main living level, "a minimum contiguous clear area of 60 SF, a minimum clear horizontal dimension of 7 FT." A balcony or roof deck counts at 50 square feet and 6 feet.
  • Recreation. Table 6.01-5A asks a project of 4 to 10 homes for one minor recreation facility, such as a tot lot, a picnic and barbecue area or a community garden. Larger projects add major facilities such as a pool or recreation building, and "Projects consisting of 45 or fewer dwellings may provide two minor recreation facilities in place of one major recreation facility."
  • What is left out. "Off-street parking spaces, drive aisles, driveways, loading areas, or service areas, shall not be included in minimum open space calculations."
  • Parking plan. Section 6.03.015 requires a Parking Management Plan with a Development Plan for a multiple-family project "which consists of 3 or more dwelling units." It assigns each resident space to a home. See the parking, setbacks and height page.

The Development Plan

A Development Plan is Ontario's review of the site plan and building design of a project. Section 4.02.025 requires it for "The development of 3 or more dwelling units on a single lot," "The development of 5 or more lots within a residential subdivision," and "The development of 5 or more dwelling units, regardless of the number of lots involved." Adding homes to an existing multiple-family project needs one "when such addition would result in 3 or more dwelling units on a single lot after the addition." Two attached homes on a lot are below every item in that list by its wording; confirm with the City before relying on it.

  • Who decides. Table 2.02-1 has one line for residential developments of 5 or more dwelling units "or the development of 3 or more dwelling units on a single lot or parcel." The Development Advisory Board recommends, the Planning Commission approves, and the City Council hears appeals.
  • Findings. The Commission must find that the project is consistent with The Ontario Plan, is "compatible with those on adjoining sites" with attention to privacy and views, will "complement and/or improve upon the quality of existing development in the vicinity," and meets the development standards and design guidelines. The application is denied if one finding cannot be made.
  • How long it lasts. "a Development Plan shall become invalid if not exercised within 24 months following the effective date of application approval," unless extended. Extensions come one year at a time, up to three.
  • Fees. The Planning fee schedule of August 22, 2026 lists Development Plan Review at $20,712.30 for less than 5 acres and $28,332.81 for 5 acres or more. Each includes a 5 percent General Plan Fee, and hearing fees are added.
  • State housing forms. The City's Applications and Resources page posts an SB 330 Preliminary Application form and an SB 6 eligibility checklist. The California permit streamlining page explains what a preliminary application does.

Objective Development and Design Standards

An objective standard is one that can be measured, such as a length in feet, as opposed to a judgment about quality. Reference J of the Development Code is the Residential Objective Development and Design Standards, or ODDS. Its cover page says it was "adopted by the Ontario City Council on April 1, 2025, by Ordinance No. 3298." The City Council agenda of March 18, 2025 introduced the ordinance under File No. PDCA24-001 and the agenda of April 1, 2025 listed it for adoption. The document says it provides "objective standards for streamlined ministerial approval of residential multiple-family and mixed- use development projects consistent with state law."

  • Where it applies. To "all multiple-family residential categories" on the General Plan land use map and to the mixed-use categories. In a specific plan or PUD, "Development applications shall utilize ODDS wherever PUD or Specific Plan standards are silent."
  • Three building types. Projects are sorted by density and building size, as the table below shows. A project under 1 acre that exceeds 25 homes per acre "can use neighborhood or housing Form in lieu of the urban massing form."
  • Height next to houses. "Buildings within 100 feet of single-family residential dwellings must not exceed 35 feet or the height of adjacent residential buildings, whichever is greater."
  • Common open space. "Common open space shall cover a minimum of 15 percent of the total lot area," and none is required "for lots within a 1/4-mile of an existing park or plaza a minimum 0.25 acres in size."
  • Private open space. "A minimum of 60 square feet of private open space shall be provided for each residential unit," with the same park exception.
  • Parking placement. "Surface parking lots shall be located at the rear, side, or internal lot lines and away from the front lot line," and where a lot has an alley, vehicle access comes from the alley.
  • Architecture. Each project selects one of six styles: "Mission-Spanish Colonial Revival, Craftsman, American Mercantile, Tuscan, Modern, or Farmhouse." The applicant fills out an ODDS checklist.
ODDS building type Applies to Setback, arterial street Collector street Local street
Urban 25 homes per acre or more 0 ft 5 ft 5 ft
Neighborhood Fewer than 25 homes per acre, with buildings of more than 5 units 10 ft 10 ft 15 ft
Housing Fewer than 25 homes per acre, with buildings of 5 or fewer units 14 ft 14 ft 20 ft

Source: Ontario Development Code, Reference J, Section 2.2 and Table 2.01 (Rev. 04.01.2025).

The two documents print different street setbacks. Table 6.01-3 asks an MDR project for 30 feet from an arterial street and 20 feet from a collector or local street. ODDS Table 2.01 prints 0 to 20 feet by building type. ODDS says its standards apply "In addition to any objective standards imposed through the underlying base zone," and Section 1.01.015 of the code says that in a conflict within the code "the more restrictive provision shall apply." Ask the Planning Department which setback it applies to your lot.

Density Bonus

The state density bonus law gives a project extra homes, and relief from some standards, when it sets aside homes at affordable prices or rents. Section 6.01.010.H applies it in Ontario to "single-family and multiple-family residential development projects, and mixed-use development projects, which contain a minimum of 5 dwelling units." Government Code 65915 defines a housing development the same way, as "a development project for five or more residential units."

  • Two procedures in one subsection. Paragraph H.3.a says a request "for a density bonus and other incentives" is processed like a Development Agreement and "shall require the approval and adoption of a Development Agreement and a Density Bonus Agreement." Paragraph H.3.b says "A request for a density bonus, in and of itself, shall not require a General Plan Amendment, Zone Change, Development Agreement, or other discretionary approval" and follows the ministerial procedure.
  • Who decides. Table 2.02-1 has both lines. "Density Bonus and Other Incentives" goes to the Planning Commission for a recommendation and the City Council for a decision, with a public hearing. "Density Bonus" alone is decided by the Planning Director.
  • What the statute says. Government Code 65915 says the granting of a concession or incentive "shall not require or be interpreted, in and of itself, to require a general plan amendment, local coastal plan amendment, zoning change, study, or other discretionary approval," and it has a matching sentence for the density bonus itself. Where the City procedure asks for more than the statute allows, the statute controls. Ask the City which procedure it uses for a project that requests incentives.
  • Grounds to refuse an incentive. The City "shall grant the requested concession or incentive" unless it finds the incentive is not needed for affordable housing costs, would have a specific adverse impact on health, safety, the physical environment or a listed historic property, or "would be contrary to state or federal law."
  • A typing error. The first finding cites "GC Section 659159(c)," which has one digit too many. The state density bonus law is Section 65915.

Government Code 65918 says "The provisions of this chapter shall apply to charter cities," so the bonus applies in Ontario whichever form of city it is.

Mixed-Use Zones, the Affordable Housing Overlay and Senior Housing

  • Mixed-use zones. The seven mixed-use districts allow 14 to 75 homes per acre. In six of them "development shall occur only after a Planned Unit Development has first been adopted for the affected property," so a builder either uses one of the 15 PUDs on the City's PUD page or applies for a new one, which the City Council adopts by ordinance. The Planning fee schedule lists a Planned Unit Development at a time and materials deposit of $10,000.00. MU-8D, at Euclid Avenue and Francis Street, uses the HDR-45 standards for homes at 20.0 to 75.0 homes per acre.
  • Commercial zones. In CN and CC, homes above or behind shops need a Conditional Use Permit, and Section 5.03.285 sets the count with an Equivalent Impact Study paid for by the applicant.
  • Affordable Housing Overlay. Inside the AH Overlay every new housing project needs "a minimum density of 20 dwelling units per acre." A project with at least 20 percent of its homes for lower income households for 30 years (Tier 1), or 25 percent (Tier 2), is "allowed by right." On overlay land with a specific plan base zone and a Medium Density Residential designation, a Tier 1 project may use the MDR-25 standards, and Tier 2 allows "a maximum density of 25 to 30 dwelling units per acre." The posted chapter ends partway through the Tier 2 rules.
  • Senior housing. Section 5.03.360 sets a base density of 25 homes per acre for senior citizen housing in CN, CC, MU-1 and MU-6, a 20 percent density bonus, and "an additional density bonus of 10%" when at least half of the added homes are affordable to very low or low income seniors. Minimum unit sizes are 450 square feet for a studio, 550 for one bedroom and 650 for two. Parking "may be as low as 0.25 spaces per rental dwelling unit," set by a parking demand study.
  • Small lot and cluster houses. Detached homes at multiple-family densities are covered on the lot size and subdivisions page.
  • ADUs on multiple-family lots. An existing multiple-family property may add up to 8 detached ADUs, capped at the number of existing homes. See the ADUs and SB 9 page.

SB 79 and Other State Laws

SB 79 is the 2025 state law that sets housing heights and densities near major transit stops. It applies county by county. Government Code 65912.156 defines its stops as ones "within an urban transit county," and HCD's advisory of March 20, 2026 says the upzoning provisions "will take effect on July 1, 2026, in Alameda, Los Angeles, Sacramento, San Francisco, San Mateo, Santa Clara, and San Diego Counties." San Bernardino County is absent from that list. The advisory adds that "the geographic scope of SB 79 is dynamic and will modify over time," so the answer can change when new rail service opens.

A search of the ten Development Code files read for this guide found no mention of SB 79, of Government Code 65912.1, or of the words inclusionary, rent control or rent stabilization. The code's own transit rule is in the HDR-45 purpose, which places that zone "generally located within 1/2-mile of a transit corridor or station." One fee refers to an affordability rule outside the code: the Ontario Ranch impact fee sheet effective July 1, 2026 lists an "Affordability In-Lieu" fee of $3.58 per square foot. The rule behind it was not found in the documents read.

Limits of This Page

The Chapter 6.0 file is named "Rev 08-18-2026" and Reference J is dated April 1, 2025. City Council agendas from January 7, 2025 to October 6, 2026 were read for later changes. The Ontario Plan, its land use map and Housing Element, the 52 specific plans, the 15 PUD documents and Reference D, the Residential Design Guidelines, were not read. Inside a specific plan, the plan's own standards replace the tables on this page. The rest of the Ontario Municipal Code is hosted by an outside publisher whose site blocks scripted requests, so any tenant or rental housing rules in it were not read. Ask the Planning Department which standards apply to your site.

Best For

  • ✓ MDR-18 and MDR-25 lots of 10,000 square feet or more, which hold three to five homes by the density ranges.
  • ✓ Sites in the Affordable Housing Overlay that can set aside 20 percent of homes for lower income households.
  • ✓ Senior housing in CN, CC, MU-1 or MU-6, with a base of 25 homes per acre and bonuses on top.

Usually Fails When

  • ✕ A triplex is planned on a 10,000 square foot MDR-11 lot, where the range allows at most two homes.
  • ✕ An HDR-45 site of less than 1.0 acre is priced at 45 homes per acre.
  • ✕ A mixed-use lot is bought for apartments and no Planned Unit Development covers it.

What To Verify Before Spending Money

  • → Which street setback the City applies: Table 6.01-3 or ODDS Table 2.01.
  • → Whether a density bonus request with incentives goes to the Planning Director or to the City Council.
  • → Whether the site is in a specific plan, a PUD, the AH Overlay or an airport safety or noise zone.

Where to Go Next

Zoning Districts
Density ranges, the rounding rule and the mixed-use zones.
Parking and Setbacks
Parking by bedroom count, guest spaces and tandem rules.
Airport Zones and Specific Plans
Where airport rules limit new homes, and how specific plans work.

Related on VanPlex: the Ontario overview, the California SB 79 page and the duplex to fourplex page.

Frequently Asked Questions

Where can I build a triplex or fourplex in Ontario, California? +
A triplex or fourplex is a multiple-family dwelling under the Ontario Development Code, and Table 5.02-1 permits that use in MDR-11, MDR-18, MDR-25 and HDR-45 and in ten of the eleven mixed-use columns. The lot must hold the count: a 10,000 square foot MDR-18 lot allows three or four homes by VanPlex arithmetic, and the same lot in MDR-11 allows two.
What permit does a project of three or more homes need in Ontario? +
A project of three or more homes on one Ontario lot needs Development Plan approval under Section 4.02.025 of the Development Code. The Development Advisory Board reviews it, the Planning Commission decides it, and the City Council hears appeals. The Planning fee schedule of August 22, 2026 lists Development Plan Review at $20,712.30 for a site of less than 5 acres, plus hearing fees.
How tall can an apartment building be in Ontario? +
Table 6.01-3 of the Ontario Development Code limits multiple-family buildings to 35 feet in MDR-11, 45 feet in MDR-18, 60 feet in MDR-25 and 75 feet in HDR-45. The 2025 design standards add a transition rule: a building within 100 feet of single-family homes must not exceed 35 feet or the height of the adjacent homes, whichever is greater. Airport height limits can be lower.
How much open space must an Ontario apartment project provide? +
An Ontario multiple-family project of more than 3 homes must provide 500 square feet of open space for each home in MDR-11 and MDR-18, 400 in MDR-25 and 310 in HDR-45, under Table 6.01-4 of the Development Code. The table splits each total into private and common space, for example 200 and 300 square feet in MDR-11, and lets the developer adjust the split.
What are the Objective Development and Design Standards in Ontario? +
The Objective Development and Design Standards, called ODDS, are Reference J of the Ontario Development Code, adopted by the City Council on April 1, 2025 by Ordinance No. 3298. They give measurable rules for multiple-family and mixed-use housing: three building types by density, façade lengths, open space, and a choice of six architectural styles. They apply in addition to the base zone standards.
How does the density bonus work in Ontario? +
Ontario follows the state density bonus law, Government Code 65915, through Section 6.01.010.H of its Development Code. It applies to projects with at least 5 homes. Table 2.02-1 lists a density bonus by itself as a ministerial decision of the Planning Director, and a density bonus with other incentives as a City Council decision after a Planning Commission recommendation.
Does SB 79 apply in Ontario, California? +
HCD, the state housing department, says in its advisory of March 20, 2026 that the SB 79 upzoning provisions took effect on July 1, 2026 in Alameda, Los Angeles, Sacramento, San Francisco, San Mateo, Santa Clara and San Diego Counties. Ontario is in San Bernardino County, which is absent from that list. The Ontario Development Code has no mention of SB 79.
Can senior housing be built in Ontario commercial zones? +
Yes, with a Conditional Use Permit in the CN and CC commercial zones. Section 5.03.360 of the Ontario Development Code sets a base density of 25 homes per acre there, a 20 percent density bonus, and a further 10 percent when at least half of the added homes are affordable to very low or low income seniors. Units start at 450 square feet for a studio.
What is the smallest site for apartments in the HDR-45 zone in Ontario? +
Table 6.01-3 of the Ontario Development Code sets a minimum project area of 1.0 acre in HDR-45, with 180 feet of width and 200 feet of depth. An existing smaller lot may still be developed, but a note to the table limits it to the minimum of the density range, which is 25.1 homes per acre. The MDR zones need 10,000 square feet.
Does Ontario have an inclusionary housing rule? +
A search of the ten Ontario Development Code files read for this guide found no use of the word inclusionary. The City impact fee sheet for Ontario Ranch, effective July 1, 2026, does list an "Affordability In-Lieu" fee of $3.58 per square foot. The rule behind that fee was not found in the documents read, so ask the Planning Department how it applies.
Does a duplex in an Ontario MDR zone need a Development Plan? +
Two attached homes on one lot fall below the list in Section 4.02.025 of the Ontario Development Code, which starts at 3 or more dwelling units on a single lot and at 5 or more homes or lots in a project. That is a reading of the list, so confirm it with the Planning Department. The multiple-family standards of Table 6.01-3 still apply.

Official sources (checked October 2026)

City of Ontario, Development Code page (chapter PDFs)
https://www.ontarioca.gov/government/community-development/planning/governing-documents/development-code
Ontario Development Code, Chapter 2.0, Administration and Procedures (PDF, Rev. 08-18-2026)
https://content.ontarioca.gov/sites/default/files/2026-09/Chapter%202.0%20-%20Administration%20and%20Procedures_Rev%2008-18-2026.pdf
Ontario Development Code, Chapter 4.0, Permits, Actions, and Decisions (PDF, Rev. 08-18-2026)
https://content.ontarioca.gov/sites/default/files/2026-09/Chapter%204%200%20-%20Permits%20Actions%20and%20Decisions_Rev%2008-18-2026.pdf
Ontario Development Code, Chapter 5.0, Zoning and Land Use (PDF, Rev. 08-18-2026)
https://content.ontarioca.gov/sites/default/files/2026-09/Chapter%205.0%20-%20Zoning%20and%20Land%20Use_Rev%2008-18-2026.pdf
Ontario Development Code, Chapter 6.0, Development and Subdivision Regulations (PDF, Rev. 08-18-2026)
https://content.ontarioca.gov/sites/default/files/2026-09/Chapter%206.0%20-%20Development%20%26%20Subdivision%20Regs_Rev%2008-18-2026.pdf
Ontario Development Code, Reference J, Residential Objective Development and Design Standards (PDF, Rev. 04.01.2025)
https://content.ontarioca.gov/sites/default/files/2025-05/Reference%20J%20Residential%20Objective%20Development%20and%20Design%20Standards_ODDS_Rev%2004.01.2025.pdf
City of Ontario, Planning Applications & Resources
https://www.ontarioca.gov/government/community-development/planning/planning-applications-resources
City of Ontario, Planning Department Fee Schedule (PDF, Rev. 08.22.2026)
https://content.ontarioca.gov/sites/default/files/2026-08/FORM_Application_Fee%20Schedule_Rev%2008.22.2026.pdf
City of Ontario, Ontario Ranch Development Impact Fees effective 07/01/2026 (PDF)
https://content.ontarioca.gov/sites/default/files/2026-07/Ontario%20Ranch%20PDF%2007.14.26_0.pdf
City of Ontario, Planned Unit Developments page
https://www.ontarioca.gov/government/community-development/planning/governing-documents/planned-unit-developments-puds
City of Ontario, City Council agenda of March 18, 2025
https://ontarioca.granicus.com/AgendaViewer.php?view_id=1&clip_id=398
City of Ontario, City Council agenda of April 1, 2025
https://ontarioca.granicus.com/AgendaViewer.php?view_id=1&clip_id=402
HCD, SB 79 advisory, March 20, 2026 (PDF)
https://www.hcd.ca.gov/sites/default/files/docs/planning-and-community/sb-79-mpo-advisory.pdf
Government Code 65915 (state density bonus)
https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=65915
Government Code 65918 (density bonus applies to charter cities)
https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=65918
Government Code 65912.156 (SB 79 definitions)
https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=65912.156
General information, not legal advice. California housing law changes every year, and each city adds its own rules on top of state law. Confirm current requirements with the city or county planning department, and with a California-licensed attorney or architect, before you buy land or file plans.

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