San Mateo regulates lot coverage through Title 27 of the zoning code. Maximum lot coverage and floor area ratio vary by zone district. ADUs of at least 800 square feet with 16-foot height and 4-foot setbacks may be built regardless of lot coverage, FAR, or open space limitations per state law.
Lot coverage and floor area ratio (FAR) in San Mateo are regulated by the development standards for each zone district in Title 27. Coverage includes all roofed structures measured at the ground level. Both lot coverage percentage and FAR limits apply — FAR measures total floor area of all stories relative to lot area. The city also requires minimum open space in residential zones. The ordinance uses daylight plane controls in addition to height and coverage limits. Notably, under state ADU law and Chapter 27.19, an attached or detached ADU of at least 800 square feet with 16-foot height and 4-foot setbacks may be constructed regardless of lot coverage, FAR, daylight plane, open space, or minimum lot size requirements. This state override prevents cities from using coverage limits to block conforming ADUs.
Exceeding lot coverage or FAR requires a variance. Building without variance approval is a code violation. ADU-specific overrides under state law cannot be denied based on coverage.
San Mateo, CA
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See how San Mateo's lot coverage limits rules stack up against other locations.
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