Unincorporated Alameda County limits maximum lot coverage to 35-45 percent in residential zones under Title 17. Coverage includes all structures with roofs, with some exemptions for uncovered decks and pervious surfaces.
Lot coverage rules in unincorporated Alameda County restrict the percentage of a parcel that may be occupied by buildings. Standard R-1 zones commonly cap coverage at 40 percent, though smaller lots (R-1-BE) or hillside parcels may allow 35 percent. Covered patios, carports, and accessory structures count toward coverage. Uncovered decks under 30 inches generally do not count. Pools and spas may be exempt depending on the zone. Hillside properties face additional floor area ratio (FAR) limits layered on top of coverage to control bulk. ADUs up to 800 square feet receive coverage exceptions under state law if strict enforcement would prevent the ADU. Planning Department calculates coverage based on the net lot area excluding private street easements.
Contact your local code enforcement office for specific penalty information.
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Side-by-side rule comparisons with other cities in Alameda County.
See how other cities in Alameda County handle lot coverage limits.
See how Castro Valley's lot coverage limits rules stack up against other locations.
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