Local zoning · Union City

Union City — Historic Preservation

Q: If my house is in Union City’s LHP overlay, do I need extra permits to replace windows or add a small deck?

It depends. The Code calls out changes to street‑facing façades, second‑story additions, and accessory structures above certain sizes as review triggers in the administrative site development review lists; minor internal work that does not change façades is less likely to trigger LHP review, but the Director can treat borderline work as a referral item. Check Chapter 18.72 (administrative review) for triggers and director referral authority. § 18.72.010

Historic Preservation under the Union City local zoning and planning code, with the controlling citations.

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Last reviewed: July 2, 2026

Overview

Union City's zoning code establishes a Landmark and Historic Preservation Overlay Zone (LHP) and integrates historic-resource review into its development-review procedures. The overlay is codified in Chapter 18.106 (range § 18.106.100 – § 18.106.420) and interacts with the City's administrative and site development review processes in Chapter 18.72 and Chapter 18.76. The rules affect alterations, additions, accessory structures and discretionary entitlements for properties that are designated or eligible for designation. § 18.106.100 ; § 18.72.010 ; § 18.76.010 .

Note: this page stays strictly within the Union City zoning/planning ordinance (Title 18) and interprets how the Code treats historic resources. For building-safety details consult the California Building Standards Code.

How Union City handles historic properties (big picture)

The City maintains a formal LHP Overlay Zone to identify and manage city-designated landmarks and historic districts; see § 18.106.100 – § 18.106.420 for the overlay chapter text and structure. § 18.106.100 .
Projects affecting properties that are in or eligible for the LHP overlay are commonly reviewed through the City's Administrative Site Development Review or full Site Development Review depending on the scope of work and potential impacts. The administrative path and its triggers are in Chapter 18.72 (§ 18.72.010 – § 18.72.105); larger or cumulatively‑impactful projects move to Chapter 18.76 (§ 18.76.010 – § 18.76.110). § 18.72.010 ; § 18.76.010 .
The administrative-review rules explicitly list the LHP Overlay Zone among the districts with special administrative review triggers (for example: second‑story additions, exterior remodels, and accessory structures over certain sizes). See the administrative review applicability lists in Chapter 18.72. § 18.72.010 .

Because historic review is implemented by overlay + the normal review procedures, you will usually interact with the Planning Division (Zoning Administrator, Planning Commission) and the City's review checklists and application procedures. See the City's standard submission/checklist flow in Chapter 18.53 and administrative review intake rules in Chapter 18.72. § 18.53.010 ; § 18.72.010 .

(Links for related review topics are placed where those words first appear.) For design and review standards you will also use the City's Development Standards, Design Review, and Parking rules.

District-by-district breakdown (how historic-pres rules interact with typical Union City districts)

Note: the LHP is an overlay (LHP) that sits on top of base zones. For parcels inside the overlay, the overlay rules and the base zone rules both apply; the overlay may impose additional review triggers and requirements. § 18.106.100 ; § 18.12.010 .

LHP (Landmark and Historic Preservation Overlay Zone)

Purpose: Establishes the City's local framework for identifying and protecting local landmarks and historic districts. See § 18.106.100 – § 18.106.420 for purpose, application and organization. § 18.106.100 .
Typical permitted uses: Uses follow the underlying base zone; overlay adds preservation-focused review requirements rather than a new list of allowed uses. See district list in § 18.12.010. § 18.12.010 .
Key development-review rules: Exterior changes (including changes to a street-facing façade), second-story additions to historic residences, and accessory structures over the stated size thresholds are called out as review triggers in the administrative-review lists; projects may require administrative site development review or full site development review depending on scope. See Chapter 18.72 and Chapter 18.76. § 18.72.010 ; § 18.76.010 .
Where it applies: On parcels that the City has mapped or designated as local landmarks or within locally designated historic districts (the overlay map and designation records are held by Planning). Verify parcel status with Planning. Verify with the jurisdiction.

RS / R‑5000 and other single‑family Residential districts (RS, R‑5000, R‑511, etc.)

Purpose and uses: Standard single‑family residential purposes and permitted uses are set in Chapter 18.32 (§ 18.32.010 – § 18.32.190). § 18.32.010 .
Typical permitted uses: One‑family dwellings, accessory uses (subject to ADU rules), home occupations, etc., consistent with Chapter 18.32. § 18.32.010 .
Key dimensional standards to check: setbacks, lot coverage, and yard rules are in Chapter 18.32 and the City's bulk regulations; the Code lists which standards continue to apply to historic/overlay cases. See § 18.32.010 and related bulk chapters. § 18.32.010 .
Historic interaction: If a home in an RS district is in the LHP overlay, changes to street‑facing façades or second‑story additions are explicit administrative-review triggers described in Chapter 18.72. § 18.72.010 .

RM (Multifamily Residential districts, e.g., RM‑1500)

Purpose and uses: Multifamily development standards and permitted uses are in Chapter 18.32 (applies to RM districts as well). § 18.32.010 .
Key standards: Off‑street parking for residential uses is applied per the RM 1500 standards in Section § 18.32.160; design and building massing are controlled by the same review chapters when work triggers review. § 18.32.160 .
Historic interaction: The administrative‑review list includes RM districts for minor projects; for historic resources, exterior modifications in RM zones that fall within the overlay will follow the LHP review triggers. § 18.72.010 .

CUL (Union Landing Commercial District) and other Commercial districts

Purpose and uses: Commercial district allowed uses and bulk rules are in Chapter 18.36 (§ 18.36.010 – § 18.36.210); CUL specifics are cross‑referenced to Chapter 18.39. § 18.36.010 .
Key standards: Off‑street parking and sign rules apply per Chapter 18.36 and Chapter 18.30; site plan and design rules (including when a project is subject to site development review) are listed in Chapter 18.76. § 18.36.150 ; § 18.76.010 .
Historic interaction: If a commercial building is within a locally designated historic district or the LHP overlay, the overlay adds review triggers (for example, certain exterior remodels or additions) and can elevate review to the Commission level. See Chapter 18.72 for referral/appeal triggers. § 18.72.010 .

-H (Hillside Combining District)

Purpose and standards: The combining district imposes hillside design and slope protection standards (see Chapter 18.96 references in the Code). Projects in the -H may be subject to the administrative review exceptions described in Chapter 18.72. § 18.96.010 — Not found in retrieved materials; see Chapter 18.72 for administrative-review language applying to the H‑District. § 18.72.010 .
Historic interaction: The Code specifically allows the Director to treat some H‑District minor projects under administrative review; if an H‑District property is also within the LHP overlay, overlay review triggers still apply. § 18.72.010 .

Most decision‑relevant standards & quick code cross‑references

Topic / Decision trigger	Short rule	Code reference
LHP overlay chapter exists	Local overlay for landmarks and historic districts; organization and scope in overlay chapter	§ 18.106.100 – § 18.106.420
Administrative site development review (minor projects)	Administrative review may apply to façade changes, 2nd‑story additions, accessory structures >450 sq ft in LHP	§ 18.72.010 – § 18.72.105
Site development review (all other projects)	Large or cumulatively‑impactful projects to Planning Commission per site development review	§ 18.76.010 – § 18.76.110
SB 9 exclusion for historic sites	SB 9 Housing Developments cannot be located within a historic district or a City‑designated landmark/district (includes LHP)	§ 18.31.010 – § 18.31.110 and explicit exclusion language in SB 9 chapter § 18.31. ; see also specific exclusion text
Parking & commercial impacts	Parking standards for commercial and residential use (used in review for historic conversions/adaptations)	§ 18.36.150

Practical guidance / interpretation (plain‑English synthesis for applicants)

If your property is listed in the local overlay or is eligible for the overlay, expect the project to be flagged for extra review: the City specifically calls out exterior façade changes, second‑story additions, and larger accessory buildings on historic properties as triggers that require administrative or Commission review under § 18.72.010. § 18.72.010 .
Small, purely internal repairs that do not change façades or building massing are less likely to trigger historic overlay review; however, “minor vs. major” determinations are made by the Director/Zoning Administrator and may be referred to the Planning Commission if there is public interest or controversy. See the Director’s referral authority and findings required for referral in Chapter 18.72. § 18.72.010 .
When the project is routed to the Planning Commission the findings required for approval are the same types used citywide (consistency with General Plan and district purpose, see Chapter 18.76). § 18.76.010 .
For historic properties you must follow normal Development Standards (setbacks, height, lot coverage), Parking and design‑review procedures; design details will be evaluated against the overlay goals in Chapter 18.106. § 18.106.100 .

Also consult the City's early preliminary review processes and the Planning Division checklists so you bring the right historic‑resource documentation up front. See the Code sections describing preliminary review and required application materials. § 18.53.010 .

Checklist

Confirm whether the parcel is within the LHP overlay (verify with Planning). § 18.106.100
Determine whether the work is a trigger (street‑facing façade change, second‑story addition, accessory structure over 450 sq ft, demolition or major alteration). § 18.72.010
Prepare application package per the City's preliminary/submittal checklists (address, APN, narrative, plans, materials). See preliminary review and application lists in § 18.53.010 and administrative review application requirements in § 18.72.
Provide photographic documentation and a description of historic significance (if property is already designated or was evaluated). Not all forms are in the zoning chapter—coordinate with Planning. Verify with the jurisdiction. § 18.106.100
Prepare to show consistency with the General Plan and applicable design guidelines (Design Review procedures) if the project escalates to site development review. § 18.76.010
Confirm parking impacts and off‑street parking numbers early (Section § 18.36.150 for commercial, § 18.32.160 for residential). § 18.36.150 ; § 18.32.160
Be aware: SB 9 ministerial approvals are explicitly not available for parcels within an historic district or City‑designated landmark/district. § 18.31.010

Risks & Ambiguities

Issue	Why it matters	What to verify
Precise LHP map / parcel inclusion	Whether the overlay applies controls the entire review path (administrative vs. discretionary)	Confirm overlay status with Planning; LHP designation is map/record‑based (verify with staff). § 18.106.100
Exact LHP design standards (e.g., "certificate of appropriateness", demolition delay)	Chapter 18.106 is the overlay chapter but the full text for demolition controls or historic‑specific standards was not recovered in full in the provided extracts	Not found in retrieved materials — Verify with the City for whether demolition restrictions, COA procedures, or specific materials guidelines exist in § 18.106.
Whether a proposed change is "minor"	The Director may treat many things as minor or refer them to the Commission; that discretion affects timeline and appeal rights	The Director's referral authority and findings are in Chapter 18.72; contact the Zoning Administrator for a pre‑application determination. § 18.72.010
SB 9 / objective ministerial eligibility for a given parcel	SB 9 is implemented differently if a parcel is in the LHP (SB9 exclusions apply)	SB 9 chapter states parcels within a historic district or City‑designated landmark/district are excluded from SB 9 ministerial approvals. Confirm parcel status and consult § 18.31.010. § 18.31.010

Plain‑English Summary

If your property is inside Union City's LHP (Landmark and Historic Preservation Overlay), expect extra review for façade work, second‑story additions, demolition, and larger accessory buildings — these projects are handled under the City's administrative or site development review processes and must show consistency with the General Plan and overlay goals. See § 18.106.100, § 18.72.010, and § 18.76.010 for the controlling rules. § 18.106.100 ; § 18.72.010 ; § 18.76.010

Source References

Union City Zoning Code — Title 18: Chapter 18.106, Landmark and Historic Preservation (LHP) Overlay Zone — § 18.106.100 – § 18.106.420.
Union City Zoning Code — Title 18: Chapter 18.72, Administrative Site Development Review — § 18.72.010 – § 18.72.105.
Union City Zoning Code — Title 18: Chapter 18.76, Site Development Review — § 18.76.010 – § 18.76.110.
Union City Zoning Code — Title 18: Chapter 18.31, SB 9 Subdivisions and Development Projects — § 18.31.010 – § 18.31.110 (includes explicit SB 9 exclusions for historic districts / landmarks).
Union City Zoning Code — Title 18: Chapter 18.32, Residential Districts — § 18.32.010 – § 18.32.190 (residential uses and bulk rules).
Union City Zoning Code — Title 18: Chapter 18.36, Commercial Districts (parking references) — § 18.36.010 – § 18.36.210; parking cited in § 18.36.150.
Application and preliminary review requirements: Chapter 18.53 (Preliminary Review / submittal checklists) and administrative application intake instructions in § 18.72.

If you need the live ordinance web link or a PDF of Chapter 18.106, request that from City Planning (their online code source is the City's Zoning Code on eCode360 — confirm current links with Planning). Verify parcel‑specific status and the City’s current overlay map with Planning staff.

Sources

Retrieved passages

Union City Zoning Code (Section 18.76.020) High relevance
Union City Zoning Code (§ 3) Medium relevance
Union City Zoning Code (§ 5) Medium relevance
Union City Zoning Code (§ 11.7) Medium relevance
Union City Zoning Code (Chapter 18.30.) Medium relevance
Union City Zoning Code (§ 7.0) Medium relevance
Union City Zoning Code (§ 4) Medium relevance
Union City Zoning Code (chapter which) Medium relevance
CFC § 6.0 (§ 6.0) Medium relevance
Union City Zoning Code (§ 2) Medium relevance
Union City Zoning Code (§ 2) Medium relevance
Union City Zoning Code (§ 5.6) Medium relevance
Union City Zoning Code (§ 2) Medium relevance
Union City Zoning Code (Title 18) Medium relevance
CBC § 4 (§ 4) Medium relevance
Union City Zoning Code (Chapter 12.75) Medium relevance
Union City Zoning Code Medium relevance
Union City Zoning Code (§ 3) Medium relevance
CBC § 5 (§ 5) Medium relevance
Union City Zoning Code (§ 2) Medium relevance
Union City Zoning Code (Chapter 18.112) Medium relevance
Union City Zoning Code (§ 2) Medium relevance
Union City Zoning Code (§ 11.0) Medium relevance

Cited sections

Official Union City code library

Frequently asked questions

What is the Landmark and Historic Preservation (LHP) Overlay Zone in Union City?

The LHP is a local overlay that identifies City‑designated landmarks and historic districts and imposes preservation‑oriented review requirements on projects that affect those properties. Its chapter runs as Chapter 18.106 (§ 18.106.100 – § 18.106.420) in the Title 18 Zoning Code. § 18.106.100

If my house is in Union City’s LHP overlay, do I need extra permits to replace windows or add a small deck?

It depends. The Code calls out changes to street‑facing façades, second‑story additions, and accessory structures above certain sizes as review triggers in the administrative site development review lists; minor internal work that does not change façades is less likely to trigger LHP review, but the Director can treat borderline work as a referral item. Check Chapter 18.72 (administrative review) for triggers and director referral authority. § 18.72.010

Who decides whether my proposed alteration to a historic building is approved?

The Zoning Administrator can approve administrative site development review items for historic properties; the Zoning Administrator may refer projects to the Planning Commission if they are controversial, major, or have cumulative impacts. The procedures are in Chapter 18.72 and, when escalated, in Chapter 18.76. § 18.72.010 ; § 18.76.010

Can I use SB 9 (split my lot or add SB9 units) if my property is in an historic district or LHP overlay?

No. The SB 9 chapter expressly excludes sites that are within an historic district or are designated/listed as a City landmark or historic property; the SB 9 eligibility rules reference historic listing as a disqualifier. See Chapter 18.31 for the SB 9 implementation and its exclusions. § 18.31.010 – § 18.31.110 ; exclusion language excerpted in the SB 9 chapter.

Will I lose the ability to modify my property if it becomes a local landmark?

The overlay adds review obligations and may elevate review to discretionary levels for work affecting external appearance, but it does not necessarily ban alterations; approval depends on consistency findings, the required findings in the review chapters, and any local design guidelines adopted for that resource. Refer to Chapter 18.106 (overlay goals) and the review findings in Chapter 18.76. § 18.106.100 ; § 18.76.010

How do I start a project review for a historic property (what forms and fees)?

Begin with the City's preliminary review and submittal checklist; discretionary or administrative site development review applications must be filed with the Director/Zoning Administrator with the standard application data (applicant name, APN/address, narrative, plans) and payment of applicable fees. See Chapter 18.53 and the administrative application rules in Chapter 18.72. § 18.53.010 ; § 18.72.010

What standards will the City apply to a proposed addition on a historic house?

The project will be judged for consistency with the General Plan, the purpose of the zoning title, the district’s requirements, and the administrative/site‑development review standards; for historic properties the LHP overlay goals in Chapter 18.106 will be part of that analysis. See § 18.76.010 (findings for site development review) and the overlay chapter § 18.106.100. § 18.76.010 ; § 18.106.100

Do I need to meet the same parking and setback standards if I convert a historic building to a new use?

Yes — underlying development standards (setbacks, parking) in the applicable chapter still apply; parking standards for commercial/residential uses are in Chapter 18.36 and 18.32 respectively, and these are considered in review. See § 18.36.150 (parking) and § 18.32.160 (residential parking). § 18.36.150 ; § 18.32.160

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