Alameda County, CA Building Safety: Building Permits (2026)
Key Facts
- Governing code
- 2025 California Building Code, county-amended
- Enforcing agency
- Alameda County Building Inspection Division
- Exempt categories
- 14 listed minor-work exemptions
- Applies to
- Unincorporated areas only, e.g. Castro Valley
Summary
Unincorporated Alameda County requires a building permit for nearly all construction under its 2025 California Building Code; only fourteen narrow categories of minor work are exempt from that requirement.
105.2 Work exempt from permit [BID][Flood]. Exemptions from permit requirements of this code shall not be deemed to grant authorization for any work to be done in any manner in violation of the provisions of this code or any other laws or ordinances of the County. Permits shall not be required for the following: (Note: Exemptions below must comply with AC Section 15.08.300 and with AC Chapter 15.40 of this title for properties located within a flood hazard area.)
Building:
1. One-story detached accessory structures accessory to Group R-3 occupancy, that are used as tool and storage sheds, playhouses and similar uses, provided the floor area is not greater than 120 square feet (11m 2 ). It is permissible that these structures still be regulated by Section 710A, despite exemption from permit.
2. Fences using concrete, masonry, or similar heavy materials not over 5 feet 9 inches (1753 mm) high or fences, other than swimming pool barriers, using light materials not over 7 feet (2134 mm) high.
3. Oil derricks.
4. Retaining walls that are not over 4 feet (1219 min) in height measured from the bottom of the footing to the top of the wall, unless supporting a surcharge or impounding Class I, II or IIIA liquids.
5. Water tanks supported directly on grade if the capacity is not greater than 5,000 gallons (18 925 L) and the ratio of height to diameter or width does not exceed 2:1.
Full Breakdown
The county's Building Inspection Division enforces the 2025 California Building Code as locally amended (Alameda County Code § 15.08.060). Section 105.2 states that permit exemptions do not authorize work that otherwise violates the code, then lists exactly fourteen exempt categories: small sheds, low fences, oil derricks, short retaining walls, small water tanks, low decks, finish work, temporary movie sets, small pools, shade structures, playground equipment, awnings, movable fixtures, and flagpoles. Everything else, including additions, new dwellings, and most remodeling, needs a permit from the Building Inspection Division before work starts. This applies only in unincorporated areas such as Castro Valley and San Lorenzo, not inside Oakland, Berkeley, or any of the county's fourteen incorporated cities.
Violations & Fines
Building without a required permit is a code violation; the Building Inspection Division can issue a stop-work order, red-tag the structure, and require a retroactive permit with added investigation fees before work resumes.
Frequently Asked Questions
Does Alameda County's building code apply inside Oakland or Berkeley?
What building code does Alameda County enforce?
Sources & Official References
Other rules in Alameda County
California rules heatmap·Compare Alameda County to another location·View the California building safety overview
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