A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateTrusted ADU Builders for San Francisco Homeowners
Adding an accessory dwelling unit in San Francisco means navigating some of the most layered permitting and zoning rules in the Bay Area, which is why many homeowners also consider ADU Builders in South San Francisco for nearby alternatives. We’ve been doing exactly that since 2006, and the single question we hear most is “who actually shows up at my door?” With Sutton ADU San Francisco, you know before we arrive. Every crew member is background-checked, identity-verified, uniformed, and photo-badged under the Threshold Standard, and we send you their name and photo ahead of the visit. Most detached ADUs in San Francisco run $180,000 to $320,000 before site work, depending on size, foundation conditions, and utility connections. Call (831) 272-7212 and we’ll give you a written price before any work begins.
Key takeaways:
- Written price delivered before any work starts, on every project, no exceptions.
- 365-Day Done Right Promise covers workmanship for a full calendar year from completion.
- Threshold Verified crew: background-checked, identity-verified, photo-badged, name and photo sent to you before arrival.
- Real ADU price ranges so you can self-qualify before you call: most detached units run $180,000-$320,000 before site work.
- Founded 2006, part of the Threshold Group family of home-service companies.
ADU Construction
ADU Construction is the full build-out of a new accessory dwelling unit, from foundation to final inspection. In San Francisco, that process includes planning review, building permits, site preparation, foundation work, framing, mechanicals, and finish carpentry and paint. Most homeowners bring us in when they’ve confirmed their lot can legally host a unit and they want one contractor accountable for the entire build rather than juggling four or five subcontractors. Detached ADU construction in San Francisco typically lands between $180,000 and $320,000 before site work, with garage conversions and JADUs running lower because the shell already exists. Sutton ADU San Francisco manages the entire sequence under one written price, so there are no surprise invoices mid-build.
Foundation and site conditions
San Francisco lots vary wildly. A flat Sunset District parcel drains and grades differently than a Glen Park slope or a Bernal Heights hillside. We walk every site before pricing, because soil movement and retaining requirements in this city can shift costs by tens of thousands of dollars if they’re not caught early.
Permit and inspection management
We pull permits, schedule inspections, and stay on the job until San Francisco’s Department of Building Inspection signs off. The written price you receive includes this management work, not as a separate line item that appears later.
Detached ADU
A Detached ADU is a freestanding second home built in the rear yard, fully separated from the primary house. It’s the right choice when you want rental income, a separate entrance for aging parents or adult children, or a dedicated home office that doesn’t share walls with your living space. In San Francisco, a detached unit usually needs its own foundation, utility connections, and often a new sewer lateral, which is why most run $180,000 to $320,000 before site work. Sutton ADU San Francisco handles the full build and connects you with the right product line for your lot, from panelized systems like Plant Prefab to custom stick-built construction.
Utility runs and sewer laterals
Detached units in older San Francisco neighborhoods frequently need new sewer lateral replacement because the existing line predates modern code. We include lateral inspections early so you’re not surprised by a $15,000-$25,000 excavation line item after construction starts.
Yard access and crane logistics
Narrow San Francisco lots sometimes require crane placement for prefab modules, which affects street permits and neighbor notifications. We handle that coordination and include it in the written price when the site assessment calls for it.
JADU
A JADU, or Junior Accessory Dwelling Unit, is a smaller unit created within the existing footprint of your home, typically under 500 square feet, with its own entrance and kitchenette but allowed to share bathroom facilities. In San Francisco, JADUs are one of the fastest paths to added living space because the city waives many fees and fast-tracks the permit review. Because the shell already exists, a JADU conversion commonly runs $80,000 to $160,000 depending on plumbing access, electrical panel capacity, and finish level. Sutton ADU San Francisco sizes the scope honestly: we’ll tell you if your existing panel can handle the load or if you need a service upgrade, and that’s all in the written price.
Interior conversions within the building envelope
A JADU means reconfiguring existing rooms, adding a door, and running a kitchenette drain line. In older San Francisco homes, that often means working around lath-and-plaster walls and cast iron plumbing, which we account for in the estimate.
Owner-occupancy considerations
San Francisco code requires owner occupancy on the lot for JADUs, which affects how you think about the unit long term. We walk through that requirement early so you understand what you’re committing to before you sign.
ADU Plans
ADU Plans are the architectural drawings, structural calculations, and site documentation required to get a building permit from San Francisco’s Department of Building Inspection. We use them to lock the scope of work, so the written price we give you reflects exactly what the city will hold us to. A full plan set for a detached ADU or garage conversion in San Francisco generally adds $8,000 to $20,000 to the project depending on complexity, and it’s included in our project pricing rather than billed as a surprise add-on. Sutton ADU San Francisco works with licensed designers and structural engineers familiar with San Francisco’s specific overlay districts and neighborhood notification requirements.
Survey, setbacks, and site documentation
A setback is the required gap between your new structure and the property line, and San Francisco enforces different setbacks for different zones and lot types. We start every plan set with a recorded survey so the drawings reflect your actual lot, not the county assessor’s approximation.
Structural engineering for Bay Area seismic loads
San Francisco building code requires structural calculations for seismic bracing, shear walls, and hold-downs that exceed what most statewide standard plans cover. Your plan set includes these calcs, engineered for your specific soil and site conditions.
ADU Contractor
An ADU Contractor is the licensed general contractor responsible for executing ADU plans, managing subcontractors, scheduling inspections, and delivering the finished unit. You need one the moment you have an approved plan set or a confirmed project scope and want a single accountable party rather than a rotating cast of subs. Full-service ADU contracting in San Francisco, where we carry the project from permit to final inspection, typically falls within the $180,000 to $320,000 range for detached units with lower figures for attached and interior conversions. Sutton ADU San Francisco brings one written price, one named project lead, and one 365-Day Done Right Promise to the job.
The written price contract
Before any work starts, you receive a written contract with fixed pricing and no scope creep passed silently to the bill. If something changes, we bring it to you in writing and get your sign-off before proceeding, never after.
Crew vetting under the Threshold Standard
Every person on your job site has passed a background check and identity verification. You get their name and photo before they arrive, and they show a photo ID badge at your door. When someone says they’re with Sutton, you can prove it before you unlock the deadbolt.
ADU Design
ADU Design is the layout, material selection, and spatial planning that makes a small unit livable rather than cramped. Good design decides whether your unit rents quickly, works for an aging parent, or functions as a true home office. Design work for a San Francisco ADU, including material selections and interior layout, is typically rolled into our project pricing, and we give straightforward guidance on kitchen placement, window sizing, and storage so your unit feels larger than its square footage. Sutton ADU San Francisco is fluent with Abodu, Cover, Dvele, Mighty Buildings, Boxabl, and Plant Prefab, so we can help you decide between a prefab line and a custom design without leaning you toward whichever one pays us more.
Matching the primary home’s character
San Francisco neighborhoods from the Richmond to Noe Valley have distinct architectural languages, and a well-designed ADU respects the primary home without mimicking it. We bias toward James Hardie siding and trim systems because they hold up in the fog belt and meet fire-resistance requirements that matter in the hills.
Small-space planning that rents or lives well
We plan for real furniture, real door swings, and real storage, not renderings. A 400-square-foot unit with the right kitchen layout and closet placement will outperform a badly planned 600-square-foot unit every time.
Backyard ADU
A Backyard ADU is simply a detached unit built in the rear yard, and it’s the most common ADU type we build in San Francisco because the city’s zoning allows rear-yard units on most lots. You need one when you have usable rear-yard space and want a separate structure rather than giving up garage parking or interior square footage. Backyard ADUs in San Francisco run $180,000 to $320,000 before site work, with the spread driven by foundation type, utility trenching distance, and whether your yard is flat or sloped. Sutton ADU San Francisco builds both panelized prefab units like those from Plant Prefab and Boxabl, and stick-built custom designs.
Garage to backyard sequencing
Some San Francisco homeowners do a garage conversion first, then a backyard unit later. We help you phase the work so the second project doesn’t require ripping up work from the first, particularly with shared utility trenches and panel loads.
Fire zone and defensible space requirements
Portions of San Francisco’s hill neighborhoods have stricter wildfire-adjacent code requirements for exterior materials and vents. We factor these into the written price rather than discovering them during framing inspection.
Brands We Service
We work regularly with Boxabl units, which are factory-built folding structures that ship as a complete module. The main thing homeowners need to know is that Boxabl still requires a San Francisco-specific foundation, utility connection, and permit set, which we handle in-house under one written price.
We also build with Plant Prefab, whose panelized wall and floor systems speed up framing significantly on tight San Francisco lots where long construction timelines are costly and disruptive. Plant Prefab units arrive as flat-packed panels and go up fast, but they require precise foundation tolerances and exact utility stub-outs. Whether you already own a Boxabl, you’re weighing Plant Prefab against a custom build, or you’re converting a Tuff Shed structure, we’ll give you honest guidance on which product line fits your lot, budget, and timeline.
Signs You Need a Pro Right Now
- Your permit application stalled or came back with objections. San Francisco’s planning department returns more ADU applications for corrections than almost any other jurisdiction in California. A contractor who works in the city weekly knows what triggers those objections before you spend another six months in review.
- Your existing foundation has visible cracks or settling. A backyard ADU needs its own foundation, but building next to a failing primary foundation can compound drainage and movement issues. A site walk catches this before you pour concrete.
- Your sewer lateral is original to a pre-1950 home. Most older San Francisco homes have clay laterals that will not pass inspection when an ADU adds new fixture units. Replacing one mid-project costs more and delays your certificate of occupancy.
- You don’t know who will actually be on your property. A construction project means multiple people in and around your home for months. If you can’t verify who they are before they arrive, that’s a legitimate reason to pause and find a builder with a documented vetting system.
- You’ve received three quotes and they vary by more than $75,000. Wildly divergent bids usually mean scope gaps, not better deals. One contractor included sewer work and another didn’t. Before you sign the cheapest number, get a written scope breakdown.
Our Process, Step by Step
- 1
Phone consultation and property walk. Call (831) 272-7212 and a live person answers. We talk through your lot, your goals, and your budget, then schedule a site visit. You receive the name and photo of the person coming to your door before they arrive.
- 2
Site assessment and feasibility review. We walk the yard, check access, measure grade changes, and review your existing sewer, electrical panel, and foundation condition. This is where we catch the expensive surprises before they become change orders.
- 3
Written scope and fixed price. You receive a written price for the entire project before any work begins. The price covers the build, permit management, inspection scheduling, and project oversight. No exceptions.
- 4
Permits, plans, and city approval. We pull permits with the San Francisco Department of Building Inspection and manage every city interaction from initial submittal through final sign-off. You don’t sit on hold with planning.
- 5
Build, inspect, and final walkthrough. Your project lead remains your single point of contact through construction, inspection, and final walkthrough. Then the 365-Day Done Right Promise begins, covering defects in workmanship for one full calendar year from project completion. If anything isn’t right, we make it right, with a free second visit included.
How Much Does ADU Builders Cost in San Francisco?
A detached ADU in San Francisco runs $180,000 to $320,000 before site work, and most homeowners land between $220,000 and $280,000 total when site preparation and utility connections are included. A garage conversion typically falls from $120,000 to $200,000. A JADU, created within your existing home footprint, usually runs $80,000 to $160,000. Those aren’t vague “starting at” numbers; they reflect what we actually see across this city’s lots.
What drives the final price: foundation type (slab versus raised versus pier), sewer lateral condition, electrical panel capacity, utility trenching distance, and whether your lot requires retaining work. The cheapest way to overpay? Sign a contract that omits sewer work or panel upgrades, then discover they’re “extra” after demolition starts. Our free estimate includes a written scope breakdown so you can compare line by line against any other bid. Call (831) 272-7212 for a written price before you make any commitment.
Our Service Area Near San Francisco
We serve the full city of San Francisco plus surrounding Bay Area communities including ADU Builders in Redwood City, ADU Builders in San Mateo, Walnut Creek, Alameda, South San Francisco, San Pablo, Novato, Pleasant Hill, Pacifica, Benicia, and San Anselmo. We schedule site assessments throughout the peninsula and East Bay, and we’ll give you a clear arrival window when you book. Our ADU Builders in San Francisco page covers the full scope of what we can build on city lots.
Serving San Francisco, CA - Our Local Coverage Area
We’re based in the San Francisco area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
Frequently Asked Questions About ADU Builders in San Francisco
An ADU builder is a general contractor who specializes in accessory dwelling units: detached backyard units, garage conversions, JADUs, and attached additions. Unlike a general remodeler who does ADUs occasionally, a specialist works in this specific San Francisco permitting environment every week, similar to how ADU Builders in Alameda navigate their own local codes. That matters because ADU code, fee structures, and planning review standards differ from standard residential remodels.
Most detached ADU projects in San Francisco take 9 to 14 months from initial site assessment to final inspection, with about 4 to 6 months of that in planning and permit review. Prefab systems like those from Plant Prefab or Boxabl can shorten the framing phase but don’t bypass city review timelines. We give you a realistic schedule in writing before work begins.
A detached ADU runs $180,000 to $320,000 before site work, garage conversions run $120,000 to $200,000, and JADUs run $80,000 to $160,000. The numbers reflect the Bay Area’s labor costs, seismic requirements, and San Francisco’s specific utility and fire-zone codes, though ADU Builders in San Francisco like Sutton keep pricing transparent and fixed. Call (831) 272-7212 for an exact written quote, estimates are free.
Yes. We have direct building experience with Boxabl, Plant Prefab, Abodu, Cover, Dvele, and Mighty Buildings, plus Tuff Shed conversions and James Hardie exterior systems. That matters because each prefab system has different foundation tolerances, utility connection points, and inspection requirements in San Francisco.
ADU construction is a planned, permitted build, not a same-day emergency service. What we do offer is a live person answering calls 24 hours a day, 7 days a week, so when you have a question about your active build or a time-sensitive issue, you’re talking to a human, not a voicemail tree. Call (831) 272-7212 anytime.
The 365-Day Done Right Promise covers defects in workmanship for one full calendar year from project completion. If something we built isn’t right, we make it right, with a free second visit included. It’s a named, written guarantee stamped on every project, not a verbal assurance.
Have your property address, lot dimensions if you know them, and any existing plans or survey documents ready. Walk the yard and note where you think the unit should go, then we’ll confirm whether that location meets San Francisco setback, fire zone, and utility requirements. One hour of your time, and the estimate is free.
Schedule Your ADU Builders Service in San Francisco Today
Call (831) 272-7212 and a live person answers, day or night. We’ll talk through your project, answer your questions, and schedule a free site assessment with no obligation. You’ll get a written price before any work begins, and you’ll know exactly who’s coming to your door before they arrive.
Written by Miles Hartwell, Owner at Sutton ADU San Francisco, serving San Francisco since 2006.
