Research by DoINeedAPermit Research Team · Updated May 2026
The Short Answer
You need a permit for every ADU in San Francisco — detached, garage conversion, junior ADU, or above-garage. California Government Code 65852.2 and later amendments (SB 9, SB 13) override local zoning and mandatory parking requirements, which is why San Francisco's approval timeline and cost are now much faster and cheaper than they were five years ago.
San Francisco is uniquely positioned as a city where state ADU law has fundamentally rewritten what you can build on your lot — and the city has leaned into that rather than fought it. While many Bay Area cities still cling to setback and lot-size restrictions, San Francisco's 2022 ADU amendments explicitly embraced AB 68 (which eliminated owner-occupancy requirements statewide), eliminated minimum lot size for detached ADUs, and made parking optional for ADUs under 750 square feet — moves that are more permissive than many peer cities in the region. The city also publishes pre-approved ADU plans on its website, which can cut your permitting timeline from 14 weeks to 4–6 weeks if your design matches one of them. Critically, San Francisco operates a 60-day 'deemed approved' shot clock under AB 671, meaning if the city doesn't issue a decision within 60 days, your application is automatically approved (with limited exceptions for traffic/design review). This is a huge advantage over Bay Area neighbors like Palo Alto or Marin County, which have no such backstop. You'll still need full building permits and inspections — foundation, framing, mechanical, electrical, plumbing — but the planning entanglement that once made ADUs cost $25K+ in San Francisco has been dramatically simplified.

What happens if you skip the permit (and you needed one)

San Francisco ADU permits — the key details

Parking, impact fees, and the timeline. San Francisco now waives parking for ADUs under 750 square feet (per the 2022 amendments), which is huge; if you're over 750 sq ft, parking is still required, though you can sometimes meet it with a tandem space on the lot or pay a $40K–$60K in-lieu fee to the city (which funds affordable housing). Impact fees (aka impact development fees) apply to all ADUs over 750 sq ft and range from $2,000–$8,000 depending on the unit size and where you are in the city (higher in central neighborhoods). The city's permitting timeline is roughly 8–14 weeks for a routine ADU, but if your project is in a historic district (e.g., Victorians in the Mission, Alamo Square, Pacific Heights), you're looking at 12–20 weeks because you'll go through Design Review. The fee structure is front-loaded: expect to pay $500–$1,200 in pre-application/permit-intake fees, $1,500–$3,000 in plan-review fees, $1,000–$2,500 in building permit fees, and $2,000–$8,000 in impact fees — total $5,000–$15,000. You'll also need a Title 24 energy audit ($300–$500) and, if your lot drains to a stormwater system (not a storm sewer), a stormwater management plan ($500–$1,500). The good news: no parking fee for sub-750-sq-ft units, which is a $40K–$60K savings. The bad news: every ADU over 400 sq ft in San Francisco now requires fire-sprinklers (per the 2024 Building Code amendments), which adds $3,000–$8,000 to construction cost and must be shown on the mechanical plans.

Three San Francisco accessory dwelling unit (adu) scenarios

Scenario A
Detached ADU, 600 sq ft, 1-bedroom, rear yard, Sunset District lot (50×100 ft), separate utilities, no historic district
You own a 5,000-sq-ft corner lot in the Sunset with a 1950s single-family home on the front 40 feet and a vacant rear yard backing to a lane. You want to build a detached 600-sq-ft ADU (1 bed, 1 bath) on the rear 30 feet of the lot, with its own driveway from the lane. This is textbook San Francisco ADU-friendly: your lot is well above 1,250 sq ft, you can meet the 5-foot rear setback (25-ft house to 30-ft rear lot line leaves plenty of room), and you have a separate alley access, so parking isn't an issue. PG&E will run a separate meter from the main service panel to the ADU (about 50 linear feet of conduit), and you'll need a separate water meter at the street (the lot line is about 20 feet from the main house meter — feasible). The city will issue a pre-application determination in 1–2 weeks confirming you don't need design review (you're not in a historic district and you're under 800 sq ft, so no fire-sprinklers are required). Plan review will be ~4–6 weeks if your architect includes egress windows (two 5.7-sq-ft windows, one on the rear, one on the side facing the neighbor), compliant foundation (12-inch crawlspace minimum for the Sunset's seasonal moisture), and a clear electrical one-line. Total permits: $2,000 (plan review + building permit + impact fees, since you're 600 sq ft and over 400 sq ft, sprinkler fees apply). Construction cost: $150,000–$200,000 (hard costs, not soft costs). Timeline: permit in 6–8 weeks, construction 5–6 months, final inspection 2 weeks. By month 10, you could be leasing it at $2,200–$2,800/month in the current Sunset market, breaking even on soft costs in 18–24 months." "fee_chips
Scenario B
Garage conversion to ADU, 750 sq ft, 1-bedroom, Cow Hollow (RH zone, no historic district), owner-occupancy NOT required
You own a 1910s Edwardian in the Cow Hollow (RH-1 zone, residential-house). The detached one-car garage in the rear is 18×20 ft (360 sq ft), and you want to expand it upward by 8 feet and add a 400-sq-ft second floor, yielding a 750-sq-ft, 1-bed ADU. You don't live in the main house (you're a landlord, not owner-occupant). Under pre-2021 law, this would be impossible; California AB 68 (2021) and San Francisco's 2022 amendments eliminated owner-occupancy as a prerequisite. You can now do this. The building department will require: (1) new foundation plans showing the existing garage foundation (likely post-and-beam on concrete piers — 1910s garage standards) and lateral-force bracing for the vertical addition (the main risk in Bay Area seismic); (2) egress plans (750 sq ft means you need two bedrooms OR one bedroom + two egress windows, and since you're doing one bedroom, you MUST show two separate egress windows, each 5.7 sq ft, on different walls — one from the bedroom, one from the living/kitchen area); (3) separate electric service (a sub-panel fed from the main house panel, about 2 breaker spaces, no separate meter on the street); (4) plumbing/mechanical plans (new 3/4-inch water line to the ADU, separate hot-water heater or point-of-use heater); (5) fire-sprinkler plans (750 sq ft triggers the 2024 Building Code requirement); (6) stormwater management plan (the new roof footprint increases impervious surface). Plan review is ~8–10 weeks because the foundation engineer will need time to review seismic bracing. The city will NOT send this to Design Review because RH zone doesn't trigger it, and the footprint isn't changing (you're vertical infill). Permit fees: $3,500 (plan review $1,500, building permit $1,000, impact fees $1,000, sprinkler plan $500). Total soft costs (architect, engineer, permits): ~$8,000–$10,000. Construction cost: $180,000–$220,000 (foundation work, vertical frame, seismic bracing, utilities, finishes). This is slower and pricier than Scenario A because of structural upgrades, but the economics still work: $2,200–$2,600/month rental income in Cow Hollow, payback in ~3 years." "fee_chips
Scenario C
Junior ADU (interior remodel), 500 sq ft, 1-bedroom, Noe Valley historic district, separate entrance from main house
You own a 1920s Colonial in Noe Valley (within the Noe Valley Historic District). Your main house is 2,000 sq ft over two stories. You want to partition off a ground-floor rear room (formerly a study), add a kitchenette (2-burner stove, small sink, mini-fridge), and create a 500-sq-ft junior ADU with its own exterior entrance (you'll cut a new door from the ground floor to the side yard). Under IRC R310 and San Francisco Code, a 'junior ADU' is technically an interior conversion, but since you're adding a separate kitchen and separate entrance, the city will likely classify it as a full ADU, not a junior ADU in the strictest sense — this is a gray area that requires a pre-application meeting with the Planning Department (1–2 weeks, free). If it's classified as a full ADU (most likely), you'll need: (1) floor plans showing the separate unit boundary (where the wall divides the main house from the ADU), (2) egress plans showing the new side-yard door meets clear-opening and descent-route requirements (IRC R310.2 — if the side yard is only 3 feet wide, you might need a landing or step), (3) plumbing/mechanical plans for the kitchenette (separate 3/4-inch water line, separate drain line, or a shared drain if the city approves — this requires a plumber's sign-off), (4) electrical plans showing a sub-panel or dedicated circuits, (5) NO fire-sprinkler requirement (500 sq ft is below the 750-sq-ft trigger, though if the combined main house + ADU exceeds some threshold, sprinklers might be required — verify with the department). However, because you're in a historic district (Noe Valley), the project WILL go through Design Review, which means you need Historic Preservation Board approval (the exterior door must match the original fenestration style, the side-yard work must not damage character-defining features). This adds 6–8 weeks to your timeline and requires a historic preservation architect ($2,000–$3,000 for drawings). Plan review: 10–12 weeks (design review + plan review). Permit fees: $2,500–$4,000 (plan review, building permit, historic review, impact fees $1,000–$1,500 if the ADU is over 400 sq ft — yes, you pay impact fees even for interior conversions). Total soft costs: $6,000–$8,000. Construction cost: $80,000–$120,000 (interior work is cheaper than detached or vertical conversion). This scenario shows how historic-district overlay adds complexity and time, and why a pre-application meeting is essential in Noe Valley. But it's still doable; the rental income ($1,800–$2,200/month) makes it worth the extra design-review hassle." "fee_chips

Every project is different.

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Why San Francisco's state-law override matters: the parking and owner-occupancy game

The practical impact: San Francisco now sees a building boom of landlord-built ADUs, whereas five years ago, most ADUs were owner-occupied ('I need rental income, so I'll move my aunt into the house and build her an ADU' — absurd). Second, the parking waiver means you don't have to sacrifice your only off-street space to the ADU, which is critical in neighborhoods like the Sunset, where lots are 50 feet wide and parking is already constrained. Third, this creates an arbitrage opportunity for small-lot owners: if your lot is 2,000–3,000 sq ft (common in SF), you can now build a detached ADU that was previously illegal, because the city had imposed a 5,000-sq-ft minimum lot size for detached ADUs (the 2022 update dropped this to 1,250 sq ft, or no minimum for garage conversions). San Francisco building permits for ADUs have quadrupled since 2022 as a result. The downside: impact fees still apply to units over 750 sq ft ($2K–$8K depending on neighborhood), and fire-sprinkler requirements (adopted 2024) add $3K–$8K in construction cost for units over 400 sq ft, so the total soft-cost burden is still $5K–$15K — not cheap, but doable where it was impossible five years ago.

The egress window trap and fire code: why two windows are often mandatory

The second-order complexity: egress windows must have a clear path to grade (or a safe exit). If your egress window opens onto a roof, you need stairs or a fixed ladder (not a fold-down ladder — that's not Code-compliant for occupied buildings). If it opens to a side yard, that yard must be at least 36 inches wide (IRC R310.2, though San Francisco often interprets this as 3–4 feet to allow emergency responder access). If your ADU is above-grade (second story or above-garage), the egress window sill must be within 44 inches of the floor, which is tight — it means the bottom edge of the window can't be higher than 44 inches from the floor. A typical 5-ft-tall window with a 2-ft sill is 3 feet of clear opening, which is 5.7 sq ft if the width is 2 ft — but that's exactly at the minimum, and any variance gets flagged. Smart designers use at least a 48-inch-wide window (or double windows, ~5 ft combined) to get 6–8 sq ft of opening, which is comfortably above Code and easier to pass review. In a 600-sq-ft ADU with a 1 bedroom, budget for at least two egress windows (one per room) at $1,000–$2,000 total (window + frame + installation). This is often overlooked in soft-cost estimates and drives change orders during construction.

San Francisco Building Department (Planning & Building)
City Hall, 1 Dr. Carlton B. Goodlett Place, San Francisco, CA 94102
Phone: (628) 652-2800 (Building Permits) or (628) 652-7400 (Planning) | https://sfgov.org/now/permit-portal (Building Permit Online Portal)
Monday–Friday 8:00 AM – 5:00 PM (closed weekends and city holidays)

Common questions

Do I need to own the main house to build an ADU in San Francisco?

No. California law eliminated owner-occupancy requirements statewide (AB 68, effective 2021), and San Francisco's 2022 ADU ordinance removed its local owner-occupancy mandate. You can be a landlord, own the main house, and rent it out while also renting the ADU. The only restriction: you can't build an ADU on a lot where the main dwelling is currently a rental ADU (preventing 'ADU stacking'); otherwise, you're free to own and rent both units.

What's the difference between a junior ADU and a full ADU in San Francisco?

A junior ADU is technically an interior conversion that creates a second dwelling unit WITHIN the existing home, typically a partitioned room with a separate entrance and kitchenette (no full kitchen). A full ADU is a separate structure (detached, garage conversion, second story) or a significantly modified space with a full kitchen (stove, oven, refrigerator). The practical distinction: junior ADUs can be faster and cheaper ($50K–$80K soft + hard costs) because they don't require a separate electrical service (you can sub-panel from the main house), and fire-sprinkler requirements may not apply if the combined house + ADU square footage stays below a certain threshold. Full ADUs require separate utilities and always trigger fire-sprinkler requirements (units over 400 sq ft). Both require permits; junior ADUs are not exempt.

How much does it cost to get a San Francisco ADU permit?

Total permit fees (not including architect/engineer) are typically $2,500–$4,500: plan-review fees ($1,000–$1,500), building-permit fees ($800–$1,200), impact fees for units over 750 sq ft ($1,000–$2,000), and fire-sprinkler plan review ($500–$800). Add soft costs (architect, engineer, pre-application, historic preservation consultant if applicable): $4,000–$10,000. Total soft costs: $6,500–$14,500. Construction is separate: $100,000–$250,000 depending on type (junior ADU is cheapest, detached is priciest, garage conversion is in the middle).

Can I build a detached ADU on a small lot in San Francisco?

Yes, as of 2022. San Francisco reduced the minimum lot size for detached ADUs from 5,000 sq ft (the old rule) to 1,250 sq ft (current rule). If your lot is 1,250+ sq ft, you can build a detached ADU. You must meet a 5-foot rear setback, 3-foot side setbacks (unless the lot is a corner, then one side can be 0 feet), and the ADU footprint can't exceed 65% of the lot area. A typical 50×100-ft Sunset lot (5,000 sq ft) easily accommodates a 600–750-sq-ft detached ADU in the rear.

Do I need fire sprinklers in my San Francisco ADU?

Yes, if the ADU is over 400 square feet. San Francisco's 2024 Building Code amendments (effective 2024) require fire-sprinkler systems in all ADUs over 400 sq ft. A 600-sq-ft ADU will need a full sprinkler system (usually a wet-pipe system fed from the main house's service line or a dedicated connection). Cost: $3,000–$8,000 depending on layout. A 400-sq-ft or smaller junior ADU may not trigger sprinklers; verify with the city in your pre-application.

What if my ADU is in a historic district like Noe Valley or Pacific Heights?

Your ADU will go through Design Review by the San Francisco Landmarks Board or, if it's within a designated historic district, the Historic Preservation Commission. This adds 6–8 weeks to your timeline and requires a Historic Preservation architect ($2,000–$4,000) to ensure the exterior changes (windows, doors, siding) match the original character. Interior conversions (junior ADUs) and detached ADUs in the rear with limited visibility may get easier approval, but expect scrutiny. Budget 12–16 weeks for permitting if you're in a historic district.

Can I use a pre-approved ADU design to speed up permitting?

Yes. San Francisco publishes pre-approved ADU plans on its website; if your project matches one of these designs (footprint, height, materials, setbacks), you can often get a ministerial permit approval (no Design Review) in 4–6 weeks instead of 8–14 weeks. Pre-approved plans cover common scenarios: 600-sq-ft detached ADU with 12-inch crawlspace, 750-sq-ft garage conversion, etc. This is the fastest path if your lot and vision fit the template.

Do I need separate utility meters for my ADU, or can I sub-meter?

San Francisco requires EITHER separate meters (one for the main house, one for the ADU) OR compliant sub-metering. For electric, a sub-panel in the main house or ADU is acceptable; for water, a sub-meter (if you can't get a separate tap) must be installed inside the main house and requires city approval. Separate water meters are preferred and cost $1,500–$2,500 (tap, meter, installation); sub-meters cost $500–$1,000 but are finickier. Show your utility plan in the permit application; the city will review feasibility with PG&E and SFPUC.

What's the 60-day 'deemed approved' rule, and does it apply to my ADU?

California Government Code 65852.2 (AB 671) requires local governments to issue a decision on an ADU permit application within 60 days or deem it approved automatically. San Francisco follows this rule, BUT it has carve-outs: projects that go through Design Review (historic districts, certain zone overlays) are NOT subject to the 60-day clock; neither are projects requiring substantial information corrections. In practice, most routine ADUs in non-historic areas do get approved or conditionally approved within 60 days if your submission is complete. Incomplete applications (missing egress plans, electrical one-line, etc.) restart the clock when you resubmit corrections.

If I build an ADU without a permit, what happens?

San Francisco Planning Enforcement will issue a planning violation notice (fines $250–$1,000/day once discovered), demand a stop-work order, and may require you to demolish the structure. Your title will be clouded (future buyers/lenders will see the violation), and you'll face a retroactive permitting process (same cost as a normal permit, ~$5K–$10K, but with penalties). Insurance won't cover unpermitted ADU injury or damage. If you lease it to a renter and they're injured, you're personally liable ($100K+). In a dense neighborhood like San Francisco, neighbors are observant and enforcement is active.

Nearby cities & related guides

Accessory Dwelling Unit (ADU) Permits in Los Angeles, CA Accessory Dwelling Unit (ADU) Permits in San Diego, CA Accessory Dwelling Unit (ADU) Permits in San Jose, CA
Disclaimer: This guide is based on research conducted in May 2026 using publicly available sources. Always verify current accessory dwelling unit (adu) permit requirements with the City of San Francisco Building Department before starting your project.

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