Alameda County, CA Building Setbacks & Zoning: Lot Coverage Limits (2026)
Key Facts
- Max lot coverage
- 40 percent
- Usable open space
- 600 sq ft per unit
- District
- R-4 (four-family) only
- Applies to
- unincorporated areas only
Summary
R-4 four-family lots in unincorporated Alameda County cannot be more than 40 percent covered by structures, and must set aside 600 square feet of usable open space per unit.
The lot coverage in R-4 districts, calculated as provided in Section 17.52.380, shall not exceed forty (40) percent of the area of the lot. It is also required that there be provided on the lot no less than six hundred (600) square feet of useable open space for each dwelling unit thereon, except as otherwise provided in Section 17.16.090.
Full Breakdown
In R-4 (four-family) districts across unincorporated Alameda County, lot coverage, calculated under Section 17.52.380, cannot exceed 40 percent of the lot area. Projects must also provide at least 600 square feet of usable open space for every dwelling unit, unless a density-and-coverage exception applies, which lets developers trade less coverage for a smaller required lot area per unit. The cap governs only unincorporated R-4 parcels, not the county's fourteen incorporated cities, each of which sets its own coverage limits.
Violations & Fines
Site plans exceeding the 40 percent coverage cap without qualifying for the density exception are rejected at plan check until building footprint or open space is adjusted.
Frequently Asked Questions
Can R-4 lot coverage exceed 40 percent in Alameda County?
Does this 40 percent cap apply to single-family R-1 lots?
Sources & Official References
Other rules in Alameda County
California rules heatmap·Compare Alameda County to another location·View the California building setbacks & zoning overview
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