Union City — Nonconforming Uses

Last reviewed: July 2, 2026

Overview

Union City's zoning title regulates nonconforming uses, buildings and structures through Chapter 18.16 (the Nonconforming Buildings, Structures and Uses chapter) and related bulk rules. The code allows legally established nonconforming conditions to continue but limits expansion, requires timely restoration after damage, and terminates nonconformities after specific periods of discontinuance or reconstruction thresholds — see § 18.16.010 – § 18.16.120 and related provisions below. Key practical controls are caps on enlargement, a six‑month discontinuance rule, and a 50% restoration threshold for buildings damaged by casualty.

How the code works (high level)

• A lawful use, building or structure that becomes nonconforming may be continued, subject to the rules in Chapter 18.16 (§ 18.16.010 – § 18.16.120) .
• Nonconforming uses of land without a structure (or accessory uses) may not be expanded beyond the area occupied at the time the ordinance made them nonconforming; if discontinued for six consecutive months they cannot be resumed (§ within Chapter 18.16).
• Nonconforming buildings have a separate set of rules (repairs/alterations, restoration after damage, and expansion limits) summarized in § 18.16.050 – § 18.16.110.
• Single‑family houses lawfully built and located in multifamily districts are given specific exemptions from repair/restoration/expansion limits (see § 18.16.050, § 18.16.080, § 18.16.100).

Note: many development questions that touch nonconforming status also interact with the city's development standards, parking, design review, overlay rules such as the Landmark and Historic Preservation (LHP) overlay, ADU policies, signage rules, and variance procedures — read those pages in parallel when you plan changes. Also verify any building work against the California Building Standards Code.

District-by-district breakdown (where this matters)

Below are the Union City districts most commonly implicated by nonconforming issues. For each district I list the district purpose, typical permitted uses, the key bulk/dimensional standards you’ll see in the code, and where that district is defined/applied in the Municipal Code.

Notes on citations: the code organizes districts and their uses across multiple chapters; the district purpose and bulk rules appear in chapters such as Chapter 18.32 (Residential), Table 18.40.020 (Industrial districts), and Table 18.41.060 (CMUE / SEE development standards). The chapter and table citations below point you to the controlling text in the Union City zoning code.

RS / R (single‑family residential)

• Purpose: Protect single‑family neighborhoods and implement the General Plan. See § 18.32.010 (Residential districts, purpose).
• Typical permitted uses: one‑family dwellings (site‑built or modular), accessory uses, carefully limited home occupations; manufactured homes under conditions are allowed. See § 18.32.010.
• Key standards (bulk): front/side/rear yards, lot area and height limits set in Chapter 18.32 and related tables (examples in Table 18.100.050 for special areas). See Chapter 18.32 and Table 18.100.050.
• Where it applies: citywide residential neighborhoods; nonconforming residential structures are subject to the Chapter 18.16 rules but detached single‑family dwellings have specific exceptions for repair and expansion in some contexts. See § 18.16.050, § 18.16.080, § 18.16.100.

RM / RM‑1500 (multifamily residential)

• Purpose: Accommodate higher density housing consistent with the General Plan. See Chapter 18.32.
• Typical permitted uses: multifamily dwellings, attached units, and limited accessory uses (see Chapter 18.32 for full list).
• Key standards: lot area, setbacks, and maximum heights are in Chapter 18.32 and tables (e.g., Table 18.102.040/100.050 for specific plan areas). Nonconforming multifamily buildings are controlled under Chapter 18.16 (repairs, restoration, expansion limits).

R‑5000 (single‑family 5,000 sq. ft. district)

• Purpose / Uses: Single‑family housing standard for typical suburban lots; rules in Chapter 18.32 and the R‑5000 district provisions.
• Notable nonconforming exception: two‑family dwellings in the R‑5000 district are addressed by § 18.88.085 (special handling noted in the nonconforming chapter). If you have a two‑family in R‑5000, check § 18.88.085 and Chapter 18.16.

MG / ML / MS (industrial districts)

• Purpose: General, Light and Special Industrial zones to accommodate manufacturing, warehousing and industrial services. See Table 18.40.020 for permitted uses and special standards.
• Typical permitted uses: manufacturing, warehousing, selected commercial/industrial services (Table 18.40.020 shows use-by-district permissions).
• Key standards: setbacks, screening and yard exceptions in Chapter 18.40; nonconforming industrial uses are allowed to continue but cannot expand and must meet the Chapter 18.16 rules.

CMUE / SEE (Corridor Mixed‑Use Employment, Station East Employment)

• Purpose: Mixed‑use/employment corridors with tailored development standards. See Table 18.41.060 (Development Standards).
• Typical uses: employment, commercial and limited mixed uses as listed for CMUE and SEE in Table 18.41.060.
• Key standards: minimum building stories, maximum height (e.g., 60 ft or 100 ft in certain subdistricts), street setbacks and landscaping percentages are shown in Table 18.41.060. Nonconforming buildings in these districts must follow Chapter 18.16 limits on enlargement and alteration.

511 Area / Specific Plan districts

• Purpose: Specific plan area with its own development standards (Table 18.100.050 and companion text). Nonconforming issues inside a specific plan area still reference Chapter 18.16 but the Specific Plan may set additional rules.

LHP overlay (Landmark & Historic Preservation overlay)

• Relevance to nonconformities: buildings located in the LHP overlay may be treated differently — the code specifically lists the LHP overlay as an allowable circumstance under which an addition to a nonconforming building may be permitted. See § 18.16.050(A)(2)(e) and Chapter 18.106 for overlay rules.

Decision‑relevant standards & permitted uses (quick table)

Checklist — what an applicant must demonstrate (nonconforming change / repair / addition)

• Demonstrate the use/structure was lawfully established prior to the ordinance or amendment that made it nonconforming (evidence: permits, dated business licenses, historical records) — Chapter 18.16 (general applicability).
• Confirm the proposed work does not expand the nonconforming land use beyond the area occupied when it became nonconforming (unless an allowed telecom co‑location exception applies) — Chapter 18.16.
• For building additions: show the addition is within the 50% floor area limit for nonconforming buildings OR obtain a variance, show PUD consistency, or demonstrate location in the LHP overlay where exception applies — § 18.16.050(A).
• If building was damaged, provide a cost estimate and show restoration costs are ≤ 50% of the cost to replace the building new, and that restoration will start within one year where applicable — § 18.16.050(D).
• If the nonconforming use was inactive, verify continuous occupancy; a lapse of six months triggers loss of nonconforming status — Chapter 18.16.
• Document any overlay or specific‑plan requirements that alter or exempt the nonconforming rule (for example, 511 Area tables or LHP overlay) — consult Table 18.100.050 and Chapter 18.106.
• If a variance is needed to keep or enlarge a nonconformity, prepare the findings required under Chapter 18.60 and the Union City Variances and Exceptions process.

Verify with the jurisdiction for parcel‑specific historic permits, utility setbacks, or public works encroachment conditions.

Risks & Ambiguities

Plain‑English summary

If your building or use in Union City was legal when it was built but no longer meets current zoning, you can usually keep it — but you generally cannot expand it, you lose the right to continue it if it sits unused for six months, and if it's badly damaged (repair cost above 50% of replacement) you must rebuild to current rules. For additions under limited circumstances there are paths (small additions, a variance, planned unit development consistency, or LHP overlay treatments) — see Chapter 18.16 and the cited sections.

Source References

• Union City Municipal Code — Chapter 18.16, Nonconforming Buildings, Structures and Uses (¶ covering § 18.16.010 – § 18.16.120).
• Union City Municipal Code — § 18.16.050 – § 18.16.110 (repairs/alterations, restoration, expansion rules).
• Union City Municipal Code — § 18.16.050(D) (restoration threshold / 50% rule).
• Union City Municipal Code — § 18.24.050(C) (special first‑floor addition allowance for single‑family with nonconforming side yards).
• Union City Municipal Code — Chapter 18.32 (Residential districts, uses and bulk rules).
• Union City Municipal Code — Table 18.40.020 (Land Use Regulations — Industrial Districts).
• Union City Municipal Code — Table 18.41.060 (Development standards for CMUE / SEE).
• Union City Municipal Code — Table 18.100.050 (511 Area standards).
• Union City Municipal Code — Index/reference list showing chapters and cross‑references (Title 18 contents).

Information Gaps

• Exact subsection number for the nonconforming land‑use discontinuance/expansion/change provisions (the chapter text is present, but the uploaded excerpt gave the language without a single explicit sub‑section number to cite). Not found in retrieved materials as a unique subsection number; see Chapter 18.16 text.
• Local interpretation guidance (administrative practice) about calculating the 50% restoration threshold (what costs are included) — Not found in retrieved materials; Verify with the City.

Retrieved passages

• Union City Zoning Code (chapter and) High relevance show source text
• Union City Zoning Code (Section 18.24.050) High relevance show source text
• Union City Zoning Code (§ 3.3) High relevance show source text
• Union City Zoning Code (§ 4.3) High relevance show source text
• Union City Zoning Code (§ 4.3) High relevance show source text
• Union City Zoning Code (§ 4.3) High relevance show source text
• Union City Zoning Code (title and) High relevance show source text
• Union City Zoning Code (Section 18.08.282.) High relevance show source text

Cited sections

• Union City Municipal Code — **Chapter 18.16, Nonconforming Buildings, Structures and Uses (¶ covering § 18.16.010 – § 18.16.120)**. (Chapter 18.16)
• Union City Municipal Code — **§ 18.16.050 – § 18.16.110** (repairs/alterations, restoration, expansion rules). (§ 18.16.050)
• Union City Municipal Code — **§ 18.16.050(D)** (restoration threshold / 50% rule). (§ 18.16.050)
• Union City Municipal Code — **§ 18.24.050(C)** (special first‑floor addition allowance for single‑family with nonconforming side yards). (§ 18.24.050)
• Union City Municipal Code — **Chapter 18.32** (Residential districts, uses and bulk rules). (Chapter 18.32)
• Union City Municipal Code — **Table 18.40.020** (Land Use Regulations — Industrial Districts).
• Union City Municipal Code — **Table 18.41.060** (Development standards for CMUE / SEE).
• Union City Municipal Code — **Table 18.100.050** (511 Area standards).
• Union City Municipal Code — Index/reference list showing chapters and cross‑references (Title 18 contents). (Title 18)
• UnionCity_ZoningCode.md

• Official Union City code library