Ontario — Overlay Districts

Last reviewed: July 3, 2026

Overview

Overlay zoning districts in the City of Ontario are special regulatory layers applied on top of the base zoning map to implement focused policy goals (agricultural transition, historic preservation, emergency shelter siting, interim reuse, affordable housing, airport safety, and transit-center transition). The controlling rules for overlays are contained in the Ontario Development Code: base overlay listings appear in § 5.01.010.F and the overlay standards and applicability are codified in § 6.01.035.

Note: first appearance links below point to other Ontario pages you will likely consult when applying (parking, design review, ADUs, development standards, etc.). Use them when the overlay interacts with those rules.

How the code organizes overlays (short)

• The Development Code lists the overlay districts by name under § 5.01.010.F. The overlay-specific development rules (purpose, applicability, standards, special approvals) are grouped under § 6.01.035 (Overlay Zoning Districts) and by the individual overlay subsections.

• Overlays apply in combination with an underlying base zoning district; uses and dimensional standards generally default to the underlying district except where the overlay explicitly modifies them. This general rule is stated in § 6.01.035.B and reinforced across individual overlay subsections.

• For land use permissions not shown in the Land Use Matrix, the code instructs use of the Zoning Administrator interpretation process; overlays can permit specific interim or additional uses by reference to Table 5.02‑1 and the overlay text. See § 5.02.010 and § 5.01.010.F.

District-by-district breakdown

Below are the overlay districts identified in Ontario’s Development Code, with the code reference and the most decision-relevant takeaways. Each subsection cites the controlling ordinance paragraph(s) and points to the file preview where the text appears.

AG — Agricultural Overlay (AG)

• Purpose: Interim preservation and regulation of agricultural uses until area develops consistent with The Ontario Plan; intended to permit agricultural operations and compatible support uses (including dairies) on a temporary basis. Code: § 5.01.010.F (listing) and § 6.01.035.C.1 (standards & applicability).
• Typical permitted uses (practical): continuing agricultural operations, agricultural support activities, dairies (subject to separation and operation rules). See the AG subsection for detailed definitions and restrictions. Code reference: § 6.01.035.C.1.
• Key development controls you must check:
  • New non-agricultural buildings (except agricultural buildings and single-family on >=10-acre lots) generally require a Specific Plan first. See: § 6.01.035.C.1.b(2).
  • Animal separation distances, manure/stockpile setbacks, and operational requirements are prescribed (examples: certain stockpile and separation distances; permanent structures and expansions may require Development Plan or CUP). See: § 6.01.035 (AG subsections) and related development standards.
  • Signs within AG have special limits (small freestanding/wall sign rules). See: § 6.01.035.C.1.q.
• Where it applies: as shown on the official Zoning Map (verify via the zoning map/Planning Department). See: § 6.01.035.C.1.b(1).

Practical guidance: Expect stricter separation and operational controls for animal-based uses; plan ahead for Specific Plan or Development Plan triggers if you propose non‑agricultural construction. Verify parcel status with the Planning Department.

EA — Euclid Avenue Overlay (EA)

• Purpose: Protect Euclid Avenue’s scenic and historic character, recognizing its National Register listing and downtown role. Code: § 5.01.010.F (listing) and § 6.01.035 (EA subsection).
• Applicability: Applies to properties inside the EA boundary on the official Zoning Map; provisions apply to all building work (including additions/remodels) whether or not a building permit is required. See: § 6.01.035 (EA applicability).
• Development standards: Projects must follow the underlying base zoning standards and the Downtown Ontario Design Guidelines (reference C). See: § 6.01.035 (EA development standards).
• Special approvals: Any Development Plan that triggers review within EA also requires a Certificate of Appropriateness under the City’s historic preservation procedures (see Historic Preservation rules). See: § 6.01.035 (EA—Certificate of Appropriateness).
• Notable use-specific limit: Medical offices/clinics located in MU‑1 with street frontage on Euclid Avenue are allowed only on the second floor or above; ground-floor occupancy is not allowed in that specific subcase. Code: § 6.01.035 (EA—medical office rule).

Practical guidance: If your project is on Euclid, plan early for design compliance and coordinate with the City’s Certificate of Appropriateness process and the Downtown Ontario Design Guidelines; see the City’s design review and historic preservation pages.

ES — Emergency Shelter Overlay (ES)

• Purpose: Implement the Housing Element by identifying areas where Emergency Shelters, Supportive Housing, Transitional Housing and Transitional Living Centers are allowed consistent with Government Code § 65583. Code: § 5.01.010.F (listing) and § 6.01.035 (ES subsection).
• Applicability: ES overlay boundaries are set by the Housing Element/Policy Plan; alternate locations may be added by City Council resolution on recommendation of the Planning Commission. See: § 6.01.035 (ES applicability).
• Permitting and standards: Within ES, those shelter-related uses are permitted by being in the overlay and are subject to the City’s temporary-shelter standards (refer to § 5.03.400) and the development standards of the underlying base zoning district (Division 6.01). See: § 5.02.010.D.4 and § 6.01.035 (ES text).

Practical guidance: If you are planning an emergency shelter or supportive housing, confirm the parcel lies within the ES boundary on the official Zoning Map and follow the temporary shelter operating standards (see § 5.03.400). Verify separation, parking, and programmatic requirements with staff.

MTC — Multimodal Transit Center Overlay (MTC)

• Purpose: Allow interim reuse of existing industrial/warehouse buildings while preserving long-term multimodal transit center vision. Code: § 5.01.010.F.4; see § 6.01.035 (MTC subsection).
• Allowed interim uses inside existing buildings: general warehousing/storage/distribution, wholesale trades, limited retail (capped at 15% of building GFA or 8,000 SF, whichever is less), and office administrative/business support services; the Zoning Administrator may approve similar uses if they are wholly contained and compatible. Code: § 5.02.010.D.5 and § 6.01.035 (MTC).
• Expansion/new construction: Any expansion or new building generally requires adoption of a Specific Plan to prescribe long-term allowed uses and standards. See: § 6.01.035 (MTC—Specific Plan trigger).
• Time-limited: The MTC Overlay has an explicit end date in the ordinance language (for the current MTC implementation the overlay remained in effect through a defined date unless extended). Check the ordinance subsection for the current sunset or extension process. See: § 6.01.035 (MTC duration/extension).

Practical guidance: If you occupy an existing warehouse in the MTC area, you can rely on interim industrial/limited retail uses but plan for a Specific Plan for major changes or expansion. Confirm whether the overlay is still active for your parcel (verify on the zoning map and with Planning).

ICC — Interim Community Commercial Overlay (ICC)

• Purpose: Allow interim community-commercial use of existing commercial buildings that are nonconforming as to zoning/land use while preserving long-term Policy Plan vision. Code: § 5.01.010.F.5 and § 6.01.035 (ICC).
• Applicability & allowed uses: Properties in the ICC follow land-use requirements of CN and CC zoning districts (see Table 5.02‑1 Land Use Matrix) for allowed interim uses. See: § 6.01.035 (ICC applicability and uses).
• Expansion limits: Building expansions are permitted only to expand an existing legally established commercial use and are subject to the CC district standards and the nonconforming structure expansion rules (Subsection 3.01.020.J). See: § 6.01.035 (ICC—expansion rules).
• Conversion to housing: New residential development in ICC locations will usually require a zone change to the applicable residential district (example cited: HDR‑45) and full compliance with that district’s standards. See: § 6.01.035 (ICC—new residential requires zone change).

Practical guidance: ICC is useful to keep commercial uses alive in older buildings, but expanding footprints or proposing housing will trigger more formal zone change/Specific Plan review.

AH — Affordable Housing Overlay (AH)

• Purpose: Facilitate housing opportunities and implement required rezonings from the City’s adopted Housing Element to comply with State housing law. Code: § 5.01.010.F.6 (AH listing).
• Detail available in code: The Development Code establishes the AH overlay as a tool for required rezone programs; specific development standards and allowed incentives are implemented where the overlay is applied or through referenced density/incentive provisions (see density bonus provisions). For precise standards, refer to the AH text where applied and density bonus rules in Division 6.01. See: § 5.01.010.F.6 and § 6.01.010.H (density bonus cross‑references).
• Practical guidance: If your property is in an AH overlay, expect implementation tied to Housing Element programs and potential use of density bonuses; verify the parcel’s AH status and the specific implementing rezoning document.

CNO — Chino Airport Overlay (CNO)

• Mentioned in the list: The CNO overlay (Chino Airport) appears in the enumeration of overlays. Code: § 5.01.010.F (listing).
• Detail available in retrieved materials: Not found in retrieved materials beyond its enumeration. Verify CNO-specific compatibility standards, safety zones, and any Airport Land Use Compatibility Plan cross-references with Planning and the ALUCP. Not found in retrieved materials.

Quick reference table — decision-relevant items

Checklist (what an applicant must satisfy when proposing work in an overlay)

• Confirm the parcel is inside the overlay boundary on the official Zoning Map (verify with Planning). See: § 6.01.035.B.
• Determine the underlying base zoning district and applicable development standards (setbacks, height, FAR) in Division 6.01 and Table 5.02‑1. See: § 5.02.010 and Division 6.01.
• For EA projects: prepare design documentation to meet the Downtown Ontario Design Guidelines and plan for the Certificate of Appropriateness if a Development Plan is required. See: § 6.01.035 (EA).
• For ES projects: satisfy the temporary-shelter operating standards in § 5.03.400, including any programmatic, distance, or management conditions. See: § 5.03.400 and § 6.01.035 (ES).
• If proposing expansion/new construction in MTC or AG, verify whether a Specific Plan or a zone change is required. See: § 6.01.035 (MTC, AG).
• Check sign, refuse, lighting, screening, and parking requirements — overlays sometimes add or modify standards; consult the City’s parking, development standards, landscaping and screening, and signage pages.
• Confirm whether design review or historic review applies (see design review and historic preservation).

Risks & Ambiguities

Plain-English summary

Overlay districts in Ontario are extra layers on the zoning map that either allow interim uses (like warehouses in the MTC or commercial uses in ICC), protect special places (Euclid Avenue), or implement housing and agricultural policy; the overlay text modifies or supplements the usual zoning rules and is enforced in tandem with the base district standards (verify overlay maps and applicable subsections before you design or apply). See: § 5.01.010.F and § 6.01.035.

Source References

• Ontario Development Code — CHAPTER 5.0: Zoning and Land Use: overlay listings, especially § 5.01.010.F (enumeration of overlays).
• Ontario Development Code — Overlay Zoning District Standards: § 6.01.035: Overlay Zoning Districts (purpose, applicability, per-overlay standards).
• Ontario Development Code — MTC uses and limits (warehouse/retail cap): Table and MTC text in Division 5.02 / § 6.01.035 (MTC subsections).
• Ontario Development Code — EA (Euclid Ave) Certificate of Appropriateness and medical office rule: EA subsection in Division 6.01.
• Ontario Development Code — ES (Emergency Shelter) cross-reference to temporary shelter standards: § 5.03.400 and ES subsection (Division 5 and Division 6).

If you need the actual ordinance PDF or the official Zoning Map extract for a parcel, request a copy of the City’s online Development Code/official zoning map or ask Planning for a parcel-specific overlay confirmation (Verify with the jurisdiction).

Retrieved passages

• Ontario Zoning Code (Section 65583.) High relevance show source text
• Ontario Zoning Code (Section 65583.) High relevance show source text
• Ontario Zoning Code (Section 4.02.025) High relevance show source text
• Ontario Zoning Code (Section 5.01.010.F.3) Medium relevance show source text
• Ontario Zoning Code (Section 5.01.010.F.4) Medium relevance show source text
• Ontario Zoning Code Medium relevance show source text
• Ontario Zoning Code (Section 4.01.035) Medium relevance show source text
• Ontario Zoning Code (Section 6.01.015) Medium relevance show source text

Cited sections

• Ontario Development Code — CHAPTER 5.0: Zoning and Land Use: overlay listings, especially **§ 5.01.010.F** (enumeration of overlays). (CHAPTER 5.0)
• Ontario Development Code — Overlay Zoning District Standards: **§ 6.01.035: Overlay Zoning Districts** (purpose, applicability, per-overlay standards). (§ 6.01.035)
• Ontario Development Code — MTC uses and limits (warehouse/retail cap): Table and MTC text in Division 5.02 / § 6.01.035 (MTC subsections). (§ 6.01.035)
• Ontario Development Code — EA (Euclid Ave) Certificate of Appropriateness and medical office rule: EA subsection in Division 6.01.
• Ontario Development Code — ES (Emergency Shelter) cross-reference to temporary shelter standards: § 5.03.400 and ES subsection (Division 5 and Division 6). (§ 5.03.400)
• Ontario_ZoningCode.md

• Official Ontario code library