Accessory Structures in South San Francisco, CA: What Residents Actually Need to Know

If you live in South San Francisco or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. South San Francisco has 4 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.

Carport Rules

South San Francisco Municipal Code Chapter 20.300 (Lot and Development Standards) and Chapter 20.330 (On-Site Parking and Loading) govern carports as accessory structures. Unlike many neighboring cities, SSFMC Section 20.330.004 expressly allows the required residential parking space to be 'within a carport or garage' — open carports are an acceptable form of required parking. Carports must comply with a minimum 5-foot setback for accessory structures, must be at least 6 feet from the main building, and accessory-building height is limited to an average of 12 feet between floor slab and ridge pole. Combined accessory-building footprint may not exceed 20 percent of the main building's footprint or 220 square feet, whichever is greater. A building permit is required.

Key details: Carport Allowed for Required Parking: Yes, under SSFMC 20.330.004. Min Setback (Accessory): 5 ft (or lot line if under 220 sq ft). Separation From Main Bldg: Min 6 ft, inclusive of roof. Max Accessory Height: 12 ft average (slab to ridge). Max Combined Footprint: 20% of main bldg or 220 sq ft, whichever greater.

Building a carport without a building permit, or one that intrudes into the 5-foot setback, exceeds the 12-foot height limit, exceeds the 20%/220 sq ft cumulative-footprint cap, or sits closer than 6 feet to the main dwelling, can result in a Code Enforcement Notice of Violation, a stop-work order, and an order to remove or modify the structure under SSFMC Chapter 20.300. Removing the required covered parking space without replacing it with another carport or garage leaves the property non-compliant with Section 20.330.004 and may block future permits (additions, ADUs, kitchen/bath remodels) until parking is restored. Continuing zoning violations are subject to administrative citations under the City's enforcement provisions.

ADU Rules

South San Francisco allows ADUs per California state law (SSFMC Title 20). Detached ADUs up to 1,200 sq ft max; minimum 800 sq ft and 16 ft allowed by right. 4-ft setbacks. ADUs cannot be STRs.

Key details: Max ADU Size: 1,200 sq ft (state law). Min Allowed by Right: 800 sq ft, 16 ft height. Setbacks: 4 ft rear and interior sides. STRs Prohibited: ADUs cannot be used as STRs. JADU: 500 sq ft max within existing structure.

Unpermitted ADU construction subject to code enforcement and fines.

Shed Rules

Small accessory structures (sheds) in South San Francisco must comply with SSFMC Title 20 setbacks. Sheds under 120 sq ft and under 8 feet generally do not require a building permit but must still meet zoning requirements.

Key details: Small Sheds: Under 120 sq ft usually no building permit. Setbacks: 4 ft from rear and side property lines. Habitable Use: Requires ADU permit. Contact: Building Division (650) 829-6670.

Unpermitted structure: retroactive permit with penalty. Non-compliant setback: modification or removal. Habitation violation: immediate correction.

Garage Conversions

Garage conversions to ADUs are permitted in South San Francisco per California ADU law. Building permit required. No replacement parking needed when converting a garage to an ADU under state law.

Key details: Permitted: Yes, per CA ADU law. Building Permit: Required. Replacement Parking: Not required (state law). Contact: Planning Division (650) 877-8535.

Unpermitted conversion: standard building code enforcement. Must bring to code or restore to garage. Safety violations: immediate correction.

The Bottom Line

South San Francisco's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming South San Francisco is broadly strict or permissive.

All of the above reflects South San Francisco's municipal code as of our last review. If you need specifics on fines, exemptions, or filing requirements, the detailed ordinance pages linked above have the full breakdown.