Do I need a permit for an ADU in
South San Francisco, California?

South San Francisco ADU permits — the key details

California state law (Government Code § 65852.2) mandates that cities approve ADUs that meet state standards, and South San Francisco's local ordinance implements this with ministerial (non-discretionary) review. Every ADU—whether detached new construction, garage conversion, junior ADU (JADU), or above-garage unit—requires a building permit. The state sets minimum floor area (430 sq ft for standard ADU, 500 sq ft for two-bedroom; JADU capped at 500 sq ft and one bedroom), and South San Francisco cannot impose stricter limits. The city must issue a permit decision within 60 days of a complete application (per AB 671 as amended by AB 881). This timeline applies only if your project qualifies as ministerial under state law: it must be on a single-family or multifamily lot, it cannot increase density beyond what the zoning allows for the primary dwelling, and it must meet all objective standards (setbacks, height, parking, etc.). If your lot is nonconforming or your project triggers discretionary design review (e.g., historic district), the 60-day clock pauses and review becomes conditional.

South San Francisco's setback and dimensional standards for detached ADUs are: 5-foot side yard, 15-foot rear yard (same as primary dwelling), 25-foot front-yard setback or 20% of lot depth (whichever is less), and 35-foot maximum height measured to eaves. These align with state minimums, so most Bay Area lots can fit an ADU. Lot size has no legal minimum per state law, but practical reality: a detached ADU on a 3,000 sq ft lot is nearly impossible given setback math. Attached ADUs (above garage, side of house) face slightly tighter standards but no setback relief. The city requires a survey showing existing improvements, setback lines, and proposed structure footprint. Parking is required at one space per ADU unless the ADU is within a half-mile of high-quality transit (CalTrain Colma or South San Francisco stations, or BART bus routes into BART); this is a huge savings. If parking is required, it can be tandem or uncovered, and it can be on the street if the street has legal capacity.

Utility connections and separate metering are mandatory for all ADUs except JADUs. Your ADU must have its own water meter and separate sewer connection (or sub-meter off the main line with independent shutoff). Electrical must be separate service or sub-panel with dedicated breaker space. Gas, if provided, must be sub-metered. Plans must show utility layout, meter locations, and isolation details; the city will not approve a unit that shares a main water shutoff or electrical panel with the primary house (except JADU, which shares utilities by definition). If your lot is served by a septic system, the ADU will require a separate tank or approved sharing agreement; most South San Francisco lots are served by municipal sewer, so this is rare. Kitchen requirements: a standard ADU must include a full kitchen (stove, oven, refrigerator, sink); a JADU has a kitchenette (may omit the oven and some jurisdictions allow efficiency cook-top). Bathroom: one full bath minimum for standard ADU, no bathroom required for JADU (though most have one).

Owner-builder rights and contractor licensing are tied to California B&P Code § 7044 and local contractor rules. You (owner) can pull the permit and perform carpentry, framing, drywall, roofing, and concrete work yourself. You cannot do electrical, plumbing, HVAC, gas, or fire-alarm work; those trades must be performed by licensed contractors (California B&P Code § 4937 for electrical, § 4950 for plumbing). Hiring unlicensed trades invalidates the permit and triggers stop-work. South San Francisco's Building Department will ask for contractor licenses at plan check and request a sign-off from the licensed electrician and plumber on the final inspection. The city offers no fast-track ADU track (unlike some CA cities with pre-approved plans), but 60 days is the default. Plan check typically takes 10–15 business days; revisions add 5–10 days. Once approved, you have 180 days to start construction or the permit lapses.

Impact fees and permit costs in South San Francisco total $5,000–$12,000 depending on unit size and scope. Residential building permit base fee is typically $10–$15 per $1,000 of construction valuation (assessed by the city, not your quote). A 600 sq ft detached ADU with slab foundation, standard framing, and finishes runs $80,000–$120,000 valuation, yielding a $800–$1,800 building permit fee. Plan-check fee is 65% of permit fee. Development impact fee for a new residential unit is approximately $3,000–$5,000 (traffic, schools, parks contributions). Connection fees for water, sewer, and electric are separate: water $500–$1,200, sewer $800–$2,000, electric $300–$800. If you are over 1,500 sq ft total lot coverage, fire sprinklers are triggered and cost $3,000–$6,000. Parking, if required, adds grading/paving ($2,000–$4,000). Most detached ADUs on South San Francisco lots do not trigger sprinklers due to modest square footage, but verify lot coverage and building footprint with the city early.

Three South San Francisco accessory dwelling unit (adu) scenarios

California State Law Overrides South San Francisco Zoning: The 60-Day Ministerial Clock

California Government Code § 65852.2, as amended by AB 68 (2021) and AB 881 (2022), mandates that every city approve ADUs that meet state objective standards. The state law is not a suggestion—it overrides any local zoning rule that would prohibit or effectively prevent ADU development. South San Francisco's local ordinance must align with state law, and the city processes ADU applications on a 60-day ministerial timeline (AB 671). Ministerial means the city cannot deny an ADU if it meets objective standards (lot size, setbacks, height, parking, etc.); the decision is a yes or a condition, never a discretionary no. This is a huge advantage compared to traditional zoning review, where a city could refuse an ADU on a single-family lot. Many Bay Area cities resisted ADU law for years, but South San Francisco has adopted a compliant local ordinance and is processing applications efficiently.

The 60-day clock starts when your application is deemed complete (usually 5–7 days after you submit). Complete means: signed application form, legal description or APN, site plan with setback lines and lot dimensions, floor plan and elevation (drawn to scale), utility layout (water, sewer, electric, gas meter locations), a survey (or title company's property description if survey is unavailable—though cities increasingly require formal survey for ADUs), and proof of ownership or authorization. Missing any of these items will generate a completeness letter, and you have 10 days to cure; only then does the clock restart. Plan check happens within the 60-day window; South San Francisco's typical plan-check turnaround is 10–15 business days. If the city has comments or requests revisions, you have 5–10 days to resubmit; revisions do NOT stop the clock—the 60 days continues running. This is different from discretionary projects, where revisions can add weeks or months.

The ministerial approval applies only to the building permit, not planning (zoning) approval. South San Francisco will issue a zoning determination letter at the same time confirming that the ADU complies with setback, height, and density rules. If your lot is in a historic district or coastal overlay, there may be additional design review, but the ADU still qualifies for the 60-day timeline because design review is not discretionary—it follows objective design guidelines. The rare exception is if your project fails a true objective standard (e.g., the ADU physically cannot fit on the lot given setbacks, or it exceeds height). In that case, the city will deny the application in writing (within 60 days) with a specific objective reason; you can then redesign and resubmit.

Parking, Utilities, and the Hidden Costs: What Actually Triggers Sprinklers and Impact Fees

Parking is the single biggest variable cost in South San Francisco ADU projects, and the state law parking waiver (within 0.5 miles of high-quality transit) can save $8,000–$15,000. If your lot is within 0.5 miles of the South San Francisco CalTrain station (downtown), the Colma CalTrain station, or a BART bus route serving BART (e.g., Route 397), you qualify for zero parking. The city measures distance from the property line to the nearest transit stop; you can request a written determination, and the city usually confirms within 5 business days. If parking is required, one uncovered space is the standard (tandem is allowed). An uncovered concrete pad (10x20 feet, 200 sq ft) costs $1,500–$2,500 to pour and finish. A covered carport adds another $3,000–$5,000. Parking in a garage (converting part of your existing garage or building new) can run $5,000–$8,000. If street parking is available and the city allows it, you can meet the requirement on-street at zero cost, but you must verify with the Planning Department—some South San Francisco blocks have HOA restrictions or limited street parking.

Utility connections are non-negotiable and are the most common plan-check hang-up. Every standard ADU must have a separate water meter (not shared with the primary house). The city's water department will install a meter at the property line or curb; your plumber then runs a service line from that meter into the ADU. Water connection fees are $800–$1,500 depending on the distance to the main and whether new main line taps are needed. Sewer is similar: a separate sewer service line from the ADU to the main sewer line in the street costs $1,200–$2,000 to connect. If you are on septic, you must either build a separate septic tank (rare in South San Francisco, which has municipal sewer) or get a legal opinion allowing a shared system (very difficult). Electrical: a separate service or sub-panel adds $600–$1,200 in materials and permits; the PG&E meter upgrade may add $300–$600. Gas: if you have gas, it must be sub-metered (a separate meter for the ADU). Many new ADUs use all-electric appliances to avoid the gas sub-meter cost and complexity.

Fire sprinklers are triggered when total building square footage on the lot exceeds 1,500 sq ft. This is often misunderstood: it is not ADU square footage alone, but the sum of the primary house and the ADU. If your house is 2,000 sq ft and your ADU is 600 sq ft, the total is 2,600 sq ft and sprinklers are required. The cost is $3,000–$6,000 depending on layout and whether you are adding to an existing sprinkler system or building new. Sprinklers add 4–6 weeks to the project timeline (design, permit, inspection). If you are under 1,500 sq ft total (very small house, small ADU), you are exempt. Development impact fees (traffic, schools, parks, infrastructure) are $3,500–$5,500 for a new residential unit in South San Francisco. These are fixed per unit, not tied to ADU size or valuation. Some cities waive these fees for ADUs; South San Francisco does not (yet). The city bundles impact fees into the permit application, and you cannot appeal them—they are set by municipal code. Plan-check and building-permit fees are based on construction valuation; the city uses a standard estimator (e.g., $50–$80 per sq ft for residential ADU work, depending on finishes).

Common questions