San Mateo County, CA Accessory Structures: Carport Rules (2026)

Carports in unincorporated San Mateo County are governed as detached accessory structures under Development Code Chapter 8.348 and through the off-street parking standards of Chapter 8.344, which provides that required parking may be provided in garages or carports. The County's floor-area definitions count the area of all garages and carports (and covered roof areas extending four or more feet from exterior walls) toward gross structure size, so a carport affects lot coverage and floor-area calculations. Section 8.348.030 addresses placement on difficult lots: where the front half of the lot slopes more than one foot of rise or fall over seven feet, or where the lot at the street line is five feet or more above or below the established street elevation, an attached or detached garage or carport may be built to the front lot line, holding the side-yard setbacks required for the main building, up to the height specified by the district or, if unspecified, a maximum of 28 feet. Like other accessory buildings, a detached carport generally must not be within 3 feet of a property line under Section 8.348.020. A building permit is generally required for carports that exceed the small permit-exempt accessory-structure thresholds.