Dixon — Historic Preservation

Last reviewed: July 2, 2026

Overview

Dixon’s Zoning Code does not contain a standalone historic-preservation chapter or an explicit local landmarking procedure in the uploaded zoning materials. Historic resources are treated primarily as constraints within other regulations (notably the residential SB9 rules and subdivision/lot-split rules) and through the City’s normal design-review and overlay tools. See the Dixon Zoning overview for context on how these regulations fit together. Verify with the jurisdiction for any locally adopted landmark ordinance or historic district map not included in the retrieved materials.

How historic preservation appears in Dixon’s Zoning Code

• The most explicit, operative references to historic resources appear as exclusions or special-locational restrictions in the RL district rules for SB9 two-unit development and for urban lot splits. Those rules prohibit SB9 development or urban lot splits within a historic district, sites on the State Historic Resources Inventory, or properties designated as local/county landmarks via ordinance. See § 18.04.040.

• There is no separate local “historic resources” chapter, no local procedures for landmark designation, and no citation in the uploaded zoning file to a municipal historic commission or to a city-level historic resource list. Not found in retrieved materials. Verify with the City Clerk / Community Development Department.

• Projects that affect the appearance of buildings or sites will often require design review under the Code; design-review criteria explicitly include building massing, exterior materials, and compatibility with adjacent properties (which is the standard tool Dixon uses to manage changes affecting historic character). See § 18.23.020 and § 18.23.050. Link: Dixon Design Review.

• Where a project is inside an adopted overlay (for example a -PD Overlay), the overlay approval and PD Plan process can include special design constraints or preservation-related conditions. See the PD/overlay findings and conditions in § 18.32.040 and § 18.32.050. Link: Dixon Overlay Districts.

• Because the Code ties some State-level historic listings into its exemptions, property status on the State Historic Resources Inventory (Public Resources Code § 5020.1) is treated as a limiting factor for certain ministerial projects (SB9 / urban lot splits). The Code references that State inventory in the SB9/urban-lot-split restrictions in § 18.04.040.

• Technical code allowances/exemptions for historic structures under the California codes (Title 24 / Building Code) are not re-written into the zoning code; building-code relief and accessibility variances for historic structures come from the adopted Building Code and related state authorities. Link: California Building Standards Code. Not found in the Dixon Zoning Code as a separate local preservation mechanism.

District-by-district breakdown (Dixon-relevant districts)

Notes: district names and standards below are pulled from the Dixon Zoning Code. Where the zoning code directly ties historic-resource treatment to a district’s rules, that is noted.

RL (Residential Low) — applicable preservation constraints

• Purpose / where it applies: The RL district is the lower-density residential district described in the residential districts chapter; see the residential development standards table. Key site rules appear in TABLE 18.04.030 and supplemental regulations at § 18.04.040.
• Historic-preservation relevance: SB9 two-unit development and SB9 urban-lot-split standards in § 18.04.040 expressly prohibit SB9 development or urban lot splits on lots that are: within a historic district, on a property included on the State Historic Resources Inventory, or designated/listed as a city or county landmark or historic property or district pursuant to a city or county ordinance. § 18.04.040 also limits demolition for SB9 work to not exceed 25 percent of existing exterior structural walls.
• Typical permitted uses and dimensional standards: single-family residences as permitted uses in RL; see TABLE 18.04.030 for minimum setbacks, maximum lot coverage, and related standards (for example 45% lot coverage for RL in the table). Link: Dixon Development Standards.
• Practical note: If you own a home in RL and are pursuing an ADU or SB9 split, check § 18.04.040 first to see if historic status blocks ministerial SB9 ministerial pathways — if so, the City may require discretionary review.

RM (Residential Medium) — general note

• Purpose / where it applies: RM supports medium-density residential uses; development standards are listed in TABLE 18.04.030 (setbacks, lot coverage, open space). TABLE 18.04.030 and the RL table entries are the controlling development standards for RM. Link: Dixon Development Standards.
• Historic-preservation relevance: The explicit SB9/urban-lot-split historic exclusions found in § 18.04.040 are written for the RL District; the Code does not reproduce the same SB9 text for RM in the retrieved snippets. That said, any exterior changes in RM remain subject to the City’s design review rules when applicable. See § 18.23.020.

CMX / DMX / CN / CR / CS (Commercial & Mixed-Use districts)

• Purpose / where it applies: These districts are defined in Chapter 18.05; the CMX / DMX land use matrix and special rules appear in § 18.05.020 and TABLE 18.05.020. Commercial districts can require design review for exterior alterations and new construction. Link: Dixon Zoning and Dixon Land Use.
• Historic-preservation relevance: The Code does not include a separate commercial historic overlay in the retrieved materials, but design-review criteria (mass, materials, streetscape) at § 18.23.060 provide the City’s primary leverage over exterior changes that could affect historic character. See § 18.23.050 and § 18.23.060. Link: Dixon Design Review.

-PD Overlay District (Planned Development) — preservation tool if applied

• Purpose / where it applies: -PD Overlay and PD Plan procedures are governed by Chapter 18.32; § 18.32.040 lists required findings for a PD Overlay, and § 18.32.050 lists conditions the City may impose. The PD mechanism can be used to attach preservation conditions or special design controls to a site. Link: Dixon Overlay Districts.
• Historic-preservation relevance: If a PD is adopted for a site containing historic resources, the PD Plan is the logical place to memorialize preservation standards, allowed alterations, or demolition limits because the PD approval can impose binding conditions.

Key decision-relevant standards (table)

Checklist — what an applicant affecting a potentially historic property must satisfy

• Determine whether the parcel is in a historic district or listed on the State Historic Resources Inventory; obtain written confirmation from City staff. Verify with the jurisdiction.
• If in RL and pursuing SB9 or an urban lot split, confirm SB9 eligibility — if the property is historic-listed the SB9 ministerial pathway is blocked per § 18.04.040.
• For any exterior change, prepare to submit for design review when the project meets criteria in § 18.23.020; address design-review criteria in § 18.23.060 (massing, materials, landscaping). Link: Dixon Design Review.
• If the property will be part of a development requiring discretionary approvals (PD, CUP, Variance), anticipate preservation/design conditions under § 18.32.050 and the Use Permit/Variance conditions chapters.
• Document demolition extent (the SB9 rule limits exterior structural-wall demolition to 25 percent in the SB9 context). § 18.04.040.
• Coordinate any building-code relief or historic-structure exceptions with the building official and refer to the California Building Standards Code for variance/alternate provisions for historic buildings. Link: California Building Standards Code.

Risks & Ambiguities

Information Gaps (what the retrieved zoning materials do NOT show)

• Any standalone Dixon “Historic Preservation” chapter, a local historic resources inventory, local landmark designation process, or a municipal historic preservation commission. Not found in retrieved materials.
• A local map (zoning map overlay) identifying “historic districts” or property lists at the city level. Not found in retrieved materials.
• Specific objective design standards (for ministerial review) tailored to prevent adverse impacts on historic properties (the Code has general design-review criteria but not a historic-specific objective ADU standard). Not found in retrieved materials; State ADU guidance discusses this subject.

Plain-English Summary

Dixon’s zoning code does not appear to run a separate local historic-preservation program in the uploaded materials; instead, the code treats historic status mostly as a limiting condition for specific ministerial pathways (notably SB9 two-unit and urban-lot-split rules in § 18.04.040) and as something the City will manage through normal design review and overlay/PD conditions. If your property might be historic, confirm the property’s official status with City staff early — it can block SB9/lot-split routes and push you into discretionary review.

Source References

• Dixon Zoning Code (Title 18), especially: § 18.04.040 (SB9/urban lot split exclusions, historic/inventory references) and TABLE 18.04.030 (residential development standards).
• Dixon Zoning Code, Design Review chapter: § 18.23.020, § 18.23.050, § 18.23.060 (applicability, scope, and criteria for design review).
• Dixon Zoning Code, PD/Overlay provisions: § 18.32.040, § 18.32.050 (findings and conditions for -PD Overlay).
• Dixon Zoning Code, Use Permits / Procedures and common procedural rules (appeals, completeness, CEQA reference) — relevant chapters 18.21, 18.24.
• State ADU guidance in the uploaded ADU handbook (background on ADUs in historic districts and what the State allows regarding objective standards).
• California Building Standards Code and Existing Building Code excerpts (uploaded) — on building-code exceptions and variance options for historic structures (Title 24 context). Link: California Building Standards Code.

Retrieved passages

• Dixon Zoning Code (§18.02.030.G) Medium relevance show source text
• Dixon Zoning Code (Section 18.21.120) Medium relevance show source text
• Dixon Zoning Code (Chapter 18.29) Medium relevance show source text
• Dixon Zoning Code (Section 21155) Medium relevance show source text
• Dixon Zoning Code (Chapter as) Medium relevance show source text
• CBC § 040 (Title 18) Medium relevance show source text
• Dixon Zoning Code (Section 5020.1) Medium relevance show source text
• Dixon Zoning Code (Section 18.30.110) Medium relevance show source text
• Dixon Zoning Code (Section 5020.1) Medium relevance show source text
• Dixon Zoning Code (§ 65915) Medium relevance show source text
• CBC § G106 (SECTION G106) Medium relevance show source text
• Dixon Zoning Code (§ 66314) Medium relevance show source text

Cited sections

• Dixon Zoning Code (Title 18), especially: **§ 18.04.040** (SB9/urban lot split exclusions, historic/inventory references) and **TABLE 18.04.030** (residential development standards). (Title 18)
• Dixon Zoning Code, Design Review chapter: **§ 18.23.020**, **§ 18.23.050**, **§ 18.23.060** (applicability, scope, and criteria for design review). (§ 18.23.020)
• Dixon Zoning Code, PD/Overlay provisions: **§ 18.32.040**, **§ 18.32.050** (findings and conditions for -PD Overlay). (§ 18.32.040)
• Dixon Zoning Code, Use Permits / Procedures and common procedural rules (appeals, completeness, CEQA reference) — relevant chapters **18.21**, **18.24**.
• State ADU guidance in the uploaded ADU handbook (background on ADUs in historic districts and what the State allows regarding objective standards).
• California Building Standards Code and Existing Building Code excerpts (uploaded) — on building-code exceptions and variance options for historic structures (Title 24 context). Link: California Building Standards Code. (Title 24)
• Dixon_ZoningCode.md
• 2025 California Building Code.md
• 2025 California ADU handbook.md

• Official Dixon code library