A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateHow Much Does an ADU Cost in San Francisco?
A detached accessory dwelling unit (ADU, or a secondary small home on your existing lot) in San Francisco typically costs between $380,000 and $650,000 in 2026. A garage conversion ADU runs $180,000 to $320,000 for a finished one-bedroom unit, while a JADU (junior accessory dwelling unit, a smaller conversion inside your primary home) lands between $120,000 and $190,000. These are real, buildable ranges for the current San Francisco market, not national averages.
San Francisco is the most expensive place to build an ADU in California. Between the city’s strict planning rules, soft-story retrofit triggers on older garages, Mandatory Inclusionary Housing requirements that sometimes hit ADU projects, and construction labor that runs 30-40% above the state average, the same 600-square-foot ADU that costs $220,000 in Sacramento can cost $480,000 here. You should know that before you sign anything.
We publish actual numbers because the old “call for a quote” game is exactly how homeowners get burned. Russ Delmar, who leads Lodgewick ADU San Francisco, has been in this market since 2010 through the Kingswell family of home-service companies, and the company’s standing rule is a written price before any work starts, every time, no exceptions.
ADU Cost Breakdown (2026)
Here’s what a detached 600-square-foot, one-bedroom ADU in San Francisco costs right now, line by line:
| Line Item | Typical Range | Notes |
|---|---|---|
| Architectural design & drafting | $18,000 – $35,000 | Includes as-built drawings, structural, Title 24 energy calcs |
| Planning & permit fees | $12,000 – $25,000 | Includes SFDBI plan check, school fees, inspection fees |
| Site prep & foundation | $35,000 – $75,000 | Slab or raised foundation, seismic anchoring, drainage |
| Framing & shell | $90,000 – $150,000 | Walls, roof, windows, weatherproofing |
| Rough plumbing | $15,000 – $30,000 | Water, drain, sewer lateral connection or new lateral |
| Rough electrical | $14,000 – $28,000 | Subpanel, new service if needed, in-wall wiring |
| Insulation & drywall | $16,000 – $28,000 | Title 24-compliant insulation levels |
| Finishes (flooring, tile, paint, trim) | $35,000 – $70,000 | Mid-range: LVP or engineered wood, standard tile |
| Kitchen (compact) | $25,000 – $45,000 | Standard appliances, butcher block or quartz counter |
| Bathroom (full) | $22,000 – $40,000 | Shower, vanity, toilet, tile walls |
| General contractor overhead & profit | $60,000 – $125,000 | Typically 15-20% on top of trades |
| Total (600 sf detached, 1BR) | $380,000 – $650,000 | $635 – $1,080 per square foot |
For a garage conversion, you’re working inside an existing structure, which removes foundation, framing, and roof costs. The tradeoff is seismic retrofitting, which San Francisco’s Department of Building Inspection regularly requires when you convert a pre-1978 garage. A finished 400-to-500-square-foot one-bedroom garage ADU in the Richmond or Outer Sunset runs $180,000 to $320,000. In the Mission or Noe Valley, where foundation conditions are tougher and access is tighter, the same conversion often lands at $250,000 to $340,000.
A JADU, which must be 500 square feet or smaller and carved out of your existing home (a converted rear bedroom, a basement with an exterior entrance, or an attached workshop), runs $120,000 to $190,000. JADUs do not require a separate kitchen, but you will need an efficiency kitchen with a sink, counter, and refrigerator.
One thing that surprises San Francisco homeowners: prefab ADUs are not a magic cost shortcut here. A Dvele or Abodu unit with a delivered shell in the $180,000-to-$250,000 range still needs a crane drop on many SF lots, foundation work, utility hookups, and local finish labor. The final installed cost usually lands within 10% of a site-built ADU, sometimes higher on lots with overhead utilities or steep driveways. Where prefab genuinely helps is time: a Cover or Abodu unit can compress your timeline by 4-to-6 months compared to a full site build, and time is money when you’re carrying a construction loan.
What Affects ADU Pricing in San Francisco
- Lot slope and retaining walls. San Francisco’s hills change everything. A flat lot in the Outer Sunset builds at the low end of our ranges. A downslope lot in Russian Hill, Glen Park, or Mount Davidson often requires engineered retaining, extra shoring, and deepened foundations, adding $40,000 to $110,000 before you hang a single sheet of drywall.
- Soft-story and seismic retrofit scope. If your garage sits beneath living space, converting it into an ADU triggers the city’s soft-story retrofit requirements. You’re looking at $25,000 to $60,000 for steel moment frames, shear walls, and foundation bolting. This is non-negotiable with the city and it is the single biggest surprise expense in San Francisco ADU conversions.
- Sewer lateral condition and location. A detached ADU in the rear yard often needs its own sewer connection. If your existing lateral runs under the proposed foundation, you either relocate it or install a new lateral to the street, which runs $8,000 to $20,000 depending on depth and distance. If the lateral is old clay pipe and fails inspection (very common in the Sunset, Richmond, and Excelsior), add another $10,000 to $15,000.
- Planning Department neighborhood notification and design review. Although ADUs are largely by-right under state law, the San Francisco Planning Department still reviews for neighborhood compatibility in some historic districts. A project in a designated historic district, like certain blocks in the Haight or Dogpatch, can add design review fees and 3-to-6 months of revision cycles, plus $5,000 to $12,000 in consultant time.
- Fog-zone material choices. The Outer Sunset, Outer Richmond, and Lake Merced sit in San Francisco’s coldest, foggiest microclimates. You need higher-grade weather barriers, better ventilation design, and materials rated for persistent moisture. James Hardie siding is a common choice there for a reason. Budget $6,000 to $15,000 more in these neighborhoods for material upgrades that keep mold and rot out.
- Access for crews and equipment. Many San Francisco lots are tight – no street parking, narrow driveway, overhead wires, neighboring structures inches from the property line. If a crane can’t reach the back yard, prefab is off the table. If crews can’t stage materials on-site, you’re paying for off-site storage and smaller deliveries, which adds $10,000 to $25,000 in logistics over the life of the project.
How Much Does Each Type of ADU Cost in San Francisco?
Detached ADU cost (new construction)
A new-detached, one-bedroom, 600-square-foot ADU in San Francisco runs $380,000 to $650,000 total, all-in. A two-bedroom, 750-to-850-square-foot detached ADU runs $480,000 to $820,000. That’s $500 to $1,100 per square foot depending on finishes, foundation, and neighborhood. For reference, the same build in Concord or Antioch runs $280,000 to $450,000. San Francisco is not a cheap place to pour concrete; the price is the price.
Garage conversion cost
A finished garage conversion ADU in San Francisco runs $180,000 to $320,000 for a one-bedroom, assuming the garage is at least 400 square feet with adequate ceiling height and a solid slab. If you have a pre-1978 garage with a living space above, expect $60,000 of that range to go directly to soft-story retrofit work the city will not let you skip.
JADU cost
A junior accessory dwelling unit inside your existing home runs $120,000 to $190,000 in San Francisco. That assumes you have a rear bedroom, finished basement, or attached space with an exterior door or a door that can be added. JADUs are the cheapest entry point and they add real rental income, but they cannot be sold separately from the home and they require the owner to live on the property if you’re renting it out.
Prefab or modular ADU cost
A prefab ADU from Abodu, Cover, Dvele, or Mighty Buildings runs $250,000 to $500,000 installed in San Francisco, including foundation, utility hookups, finishes, and local permitting. The factory price is only part of the story: a Abodu Studio 500 lists around $160,000 to $220,000 for the module itself, but you’ll add $80,000 to $200,000 in San Francisco site costs, utility work, and labor. We work with these manufacturers directly and the numbers hold steady every time.
Above-garage ADU cost
An ADU built over a new or existing garage runs $420,000 to $700,000 in San Francisco for a one-bedroom. It is the most expensive ADU type because you’re paying for a garage structure on the ground floor plus living space above, and the structural engineering load requirements are heavier than a single-story build. That said, it preserves your rear yard, which matters on San Francisco’s famously small lots.
San Francisco Permits and Soft Costs
Every San Francisco ADU project goes through the Department of Building Inspection (SFDBI) and the Planning Department. Here are the line items you’ll hit before construction starts:
- Building permit fee: $5,000 to $12,000 based on valuation
- Planning Department review: $2,000 to $5,000, more in historic districts
- School impact fees: $4 to $5 per square foot for ADUs over 750 square feet, under the current fee schedule
- Soft-story retrofit permit: $1,500 to $3,000 when triggered
- Architectural and engineering plans: $18,000 to $35,000, depending on site complexity
- Title 24 energy compliance: $1,500 to $3,000 for calculations and paperwork
- Geotechnical report: $4,000 to $9,000, required on sloped lots or where soil conditions are unknown
- Survey of existing conditions: $1,500 to $3,000
Plan approval timelines currently run 4-to-8 months for a standard over-the-counter ADU review, longer for projects requiring neighborhood notification. That’s before you get a shovel in the ground. If you want a real number for your specific lot, call (707) 760-0502 and we’ll put one in writing.
Cost per Square Foot: San Francisco vs. Other Bay Area Markets
Here’s the square-foot comparison that actually matters to San Francisco homeowners:
| Market | Detached ADU Cost per Sq Ft (2026) |
|---|---|
| San Francisco (citywide average) | $635 – $1,080 |
| Oakland / Berkeley | $450 – $750 |
| Daly City / South San Francisco | $420 – $680 |
| Marin County | $520 – $850 |
| San Jose / Peninsula | $480 – $800 |
You’re paying a San Francisco premium for a reason: union labor requirements on certain project sizes, seismic standards that are stricter than almost anywhere else in the country, access and logistics costs on dense hillside lots, and the city’s famously slow, detail-oriented review process. When you see a national ADU cost article claiming $150,000 for a detached unit, that number does not exist in this city. Budget with local numbers or you will run out of money halfway through the build.
How to Save on an ADU in San Francisco
Savings are real here, but they come from design decisions, not cheap labor:
- Convert a garage instead of building new. A garage conversion saves you $200,000 to $330,000 compared to a detached ADU. If your garage qualifies, this is the biggest single savings move in San Francisco.
- Build a JADU before you build a full ADU. A JADU inside your existing home is the cheapest legal rental unit in California. Some owners do a JADU first, rent it, then use the income to finance a detached ADU later.
- Keep the footprint modest. Every 100 square feet of ADU adds roughly $60,000 to $110,000 in San Francisco. A 495-square-foot unit costs dramatically less than a 750-square-foot unit, and there’s no square-footage minimum for livability when it’s designed well.
- Choose standard finishes from the start. Quartz countertops instead of marble, LVP flooring instead of hardwood, standard appliance packages instead of luxury lines. You can save $25,000 to $50,000 without changing the structure or the livability.
- Use prefab where the site allows it. If your lot is flat with crane access, a prefab ADU from Boxabl, Abodu, or Plant Prefab can cut 4-to-6 months off your timeline and reduce your holding costs significantly, even if the sticker price is comparable to site-built.
- Get a written price before any work starts. That’s how the Kingswell Guarantee works: Lodgewick ADU San Francisco puts the price in writing first, shows up in the window we give you, keeps the job site clean, and gives you a written guarantee on every project. You shouldn’t have to guess, and you shouldn’t have to call three times to get a ballpark. Call (707) 760-0502 and you’ll get a live person, 24/7, and a free written estimate.
The 365-Day Done Right Promise and Written Guarantee
Every ADU build or garage conversion through Lodgewick ADU San Francisco includes the 365-Day Done Right Promise. Here’s what that means in plain English: if the work is not done right, we come back and make it right. That commitment is in writing before the first nail is driven. If something fails within the guarantee period, you get a free return visit. No phone tag, no argument, no “that’s normal settling.”
It also means a few other things that shouldn’t feel revolutionary but are, in this market:
- A written price before any work starts. Not an estimate you pray holds. Not a range that creeps. A number, in writing, on every project, no exceptions.
- A real arrival window. We show up when we say we’ll show up. In a city where “contractor time” is a punchline, we run a schedule and we keep it.
- A clean job site. The Kingswell Way says the crew leaves the site cleaner than they found it, every single day, not just on the final walkthrough.
- Background-checked, uniformed technicians. You will always know who is on your property. No mystery subcontractors, no unannounced crews.
When you’re spending $380,000 or more on a structure that will house your aging parent, your adult kid, or a paying tenant, the written guarantee is not a nice-to-have. It’s the only reason to sign the contract. The name Lodgewick comes from an old word for a small house on a larger property, which is exactly what an ADU is: a smaller home within the boundary of your existing home’s lot. We build small houses on big property. That’s the whole job.
Working With Lodgewick ADU San Francisco
Lodgewick ADU San Francisco is the ADU company of the Kingswell family. We’ve been building accessory dwelling units, garage conversions, and home additions since 2010. We work with leading prefab and materials brands including Abodu, Cover, Dvele, Mighty Buildings, Boxabl, Plant Prefab, Tuff Shed, and James Hardie, and we match the right system to your lot, budget, and timeline instead of trying to force your project into one product.
Russ Delmar leads the San Francisco team. When you call, a live person answers, 24/7. Not a voicemail loop, not a chatbot. A person who can answer questions about your build, your budget, or your guarantee. If you’re at the stage where you’re just trying to understand what’s possible on your lot, call (707) 760-0502 for a free written estimate. You’ll get straight numbers, a clear breakdown, and no pressure.
ADU Cost Calculator: Quick Reference
Here’s the short version for a fast read:
- 1-bed detached ADU (600 sf): $380,000 – $650,000
- 2-bed detached ADU (750 sf): $480,000 – $820,000
- Garage conversion (1-bed): $180,000 – $320,000
- JADU (under 500 sf): $120,000 – $190,000
- Prefab ADU installed: $250,000 – $500,000
- Above-garage ADU (1-bed): $420,000 – $700,000
These are 2026 numbers for the San Francisco market. They reflect current material costs, labor rates, and City and County of San Francisco permit fees. If someone quotes you $150,000 for a new detached ADU in this city, ask what’s excluded, because something is.
FAQs – ADU Cost in San Francisco
How much does an ADU cost in San Francisco in 2026?
A detached ADU in San Francisco costs $380,000 to $650,000 for a typical one-bedroom unit. A garage conversion runs $180,000 to $320,000, and a JADU runs $120,000 to $190,000. Call (707) 760-0502 for a written estimate on your specific lot, free.
Is it cheaper to build an ADU or convert a garage in San Francisco?
A garage conversion is significantly cheaper than a new detached ADU in San Francisco, typically $180,000 to $320,000 versus $380,000 to $650,000. The catch is seismic retrofit work, which adds $25,000 to $60,000 on many older garages. We can assess your garage’s retrofit exposure quickly and give you a real number.
How much does a JADU cost in San Francisco?
A junior accessory dwelling unit in San Francisco costs $120,000 to $190,000 for a finished space under 500 square feet carved from your existing home. JADUs are the cheapest legal unit type, but they cannot be sold separately from the house and owner-occupancy rules apply if you rent. Call (707) 760-0502 for a JADU feasibility check on your floor plan.
How much does a prefab ADU cost installed in San Francisco?
A prefab ADU from Abodu, Cover, Dvele, Mighty Buildings, or Boxabl costs $250,000 to $500,000 installed in San Francisco, including foundation, utilities, permit work, and finishes. The factory module is only part of the cost; site work and utility hookups add significantly. We work with all of these manufacturers and can quote both prefab and site-built so you can compare real numbers.
How long does it take to build an ADU in San Francisco?
Plan and permit approval in San Francisco takes 4 to 8 months for most ADU projects. Construction takes 6 to 12 months for a site-built detached ADU, 3 to 6 months for a garage conversion, and 2 to 5 months for a prefab installation once the site is ready. Call (707) 760-0502 and we’ll give you a realistic timeline for your specific project.
What’s the cheapest ADU I can build in San Francisco?
A JADU inside your existing home is the cheapest legal option, at $120,000 to $190,000. The second cheapest is a garage conversion at $180,000 to $320,000. Both are dramatically less expensive than new detached construction, and both can be the right call depending on your lot and your goals. A free written estimate from Lodgewick ADU San Francisco will lay out both options side by side.
Written by Russ Delmar, who leads Lodgewick ADU San Francisco. Pricing reflects the San Francisco market as of 2026. Lodgewick ADU San Francisco offers free estimates – call (707) 760-0502.
What Our Customers Say
"The ADU came out beautiful and the permitting, which terrified me, was handled start to finish. They kept me updated every week so I was never wondering what was happening."
- Shauna Mills"Turned our detached garage into a little guest house. Clean crew, respectful of the neighbors, and no mystery charges at the end. Love how it turned out."
- Carmela Fontes"I was nervous about adding on but they walked me through every step and every cost before we started. No surprise change orders halfway through like I'd heard horror stories about."
- Eleanor Pratt
