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Alameda County, CA Sign Regulations: Window Signs (2026)

Some Restrictions
Compiled from the official code textEditor Martyn O'NeillLast verified August 2026

Key Facts

Window sign cap
25% of window area
Applies to
unincorporated Alameda County only
Excess signage
counts toward aggregate sign area
Governing law
Title 17 Zoning, Ch. 17.52

Summary

In unincorporated Alameda County, signs viewed through a window count toward the property's total sign area only if they cover more than 25% of that window's area.

City-specific rules exist: Fremont, Berkeley, Oakland, Hayward, and San Leandro have their own window signs rules that differ from Alameda County's county-level regulations. If you live in one of those cities, check the city-specific page instead.

Signs located inside a building or structure, provided any such sign is neither attached to windows with its sign copy visible from the outside nor otherwise so located inside so as to be conspicuously visible and readable without intentional and deliberate effort from outside the building or structure, provided, however, that any sign or signs which in the aggregate have an area not exceeding twenty-five (25) percent of the window area from which they are viewed are also permitted and need not be included in any computation of permitted aggregate sign area.

View official code

Full Breakdown

Alameda County's zoning code permits window and other signs viewed through building windows without counting them toward a property's total allowed sign area, as long as they cover no more than 25% of the window area from which they're viewed. Signs exceeding that share must be included in the aggregate sign-area computation for the site. This rule governs unincorporated Alameda County only, Castro Valley, San Lorenzo, Ashland, Sunol and similar communities, not Oakland, Berkeley or the county's other incorporated cities, each of which sets its own sign code.

Violations & Fines

Signs exceeding the 25% window-area threshold count toward the property's total permitted sign area and can trigger zoning code enforcement by the Alameda County Planning Department, including required removal or reduction.

Frequently Asked Questions

Does this rule apply inside Oakland or Berkeley?
No. Alameda County's zoning code governs only unincorporated areas like Castro Valley and San Lorenzo; Oakland, Berkeley and the county's other cities set their own sign rules.
What counts toward the 25% window sign limit?
Any sign attached to a window or otherwise visible through it from outside; once such signage exceeds 25% of that window's area, it must be counted in the property's permitted aggregate sign area.

Sources & Official References

Other rules in Alameda County

Political SignsLight RestrictionsParking Rules: Commercial & Oversized VehiclesSignificant RestrictionsParking Rules: Preferential Parking DistrictsSome RestrictionsParking Rules: Loading ZonesSome RestrictionsLandscaping Rules: Tree Removal & Heritage TreesSome RestrictionsWater Use Rules: Recycled Water RulesLight RestrictionsHistoric Preservation: Historic-Cultural MonumentsSignificant Restrictions

All Alameda County rules

California rules heatmap·Compare Alameda County to another location·View the California sign regulations overview

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Window Signs in Cities Across Alameda County

Oakland, CAFremont, CAHayward, CABerkeley, CASan Leandro, CALivermore, CACastro Valley, CA