Union City, CA Sign Regulations: Window Signs (2026)
Key Facts
- Coverage cap
- 25% of window surface area
- Illumination
- No flashing or intermittent lighting
- Permit
- Not required if compliant
- Over the cap
- Becomes a prohibited sign
Summary
Union City exempts window signs from permit review only if they cover no more than 25% of the window's surface area and don't flash: exceed that and the sign becomes an outright prohibited sign.
Window signs are subject to the following restrictions:
1. The sign area allowed for window signs shall not exceed 25% of the surface area of the window;
2. Such signs shall not exhibit flashing or intermittent illumination.
I. Home occupation signs advertising an approved home occupation conducted on the premises, provided that such sign shall be naturally illuminated, shall not exceed one and one-half (1-1/2) square feet in area, and shall be located flat against the wall or window of the dwelling.
J. Building marker signs provided that the sign only includes the building name, date of construction, or historical data on a historic site. The sign must be cut or etched into masonry, bronze or similar material. Such signs shall not exceed two square feet in area and shall be naturally illuminated.
K. Flags of the United States, the State of California, the City of Union City, foreign nations, and any other flag adopted or sanctioned by an elected legislative body of competent jurisdiction.
L. Political Signs. Temporary political signs provided that such signs comply with the following conditions:
1.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4940544; v16 updated 2026-06-23).
Full Breakdown
Under Union City Municipal Code § 18.30.040(H), window signs are automatically exempt from the sign application process citywide, but only within a hard cap: sign area may not exceed 25% of the window's surface area, and the sign can't use flashing or intermittent illumination. Go over that 25% ceiling and the display flips from exempt to expressly prohibited under § 18.30.050(K), regardless of the property's zoning district. The rule applies the same way to every window sign in the city, whether a retail storefront display or a home business notice, with no separate permit fee or design review as long as the coverage and illumination limits are met.
Violations & Fines
Exceeding 25% window coverage converts the sign into a prohibited sign under § 18.30.050(K); the city can require removal or reduction as unpermitted signage under § 18.30.020.
Frequently Asked Questions
Do I need a permit for a window sign in Union City?
What happens if my window sign covers more than 25% of the window?
Sources & Official References
Other rules in Union City
California rules heatmap·Compare Union City to another location·View the California sign regulations overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.
Window Signs in Nearby Cities
How other cities in Alameda County handle window signs.