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San Francisco · Custom ADU
A San Francisco ADU drawn for your lot, your flat, and the family in it.
Sunset garage conversions, Noe Valley rear in-law units, deep skinny lots that won't take a catalog plan — our designer draws a bespoke unit around your exact SF parcel, then we build it.
Trusted by homeowners across Sacramento & surrounding areas.
Custom ADU in San Francisco — fast facts
City
San Francisco
ADU type
Custom ADU
Contractor license
CSLB #1119373
Free estimate
(916) 677-9774
Last updated
Why custom in San Francisco
When the lot decides, not the plan
A stock detached plan assumes a generic family on a flat, cooperative rectangle with room to spare. San Francisco hands you the opposite of all three. The lots here are tiny and deep, the homes are stacked two and three stories, and land value is so high that nobody wastes a square foot. We get the calls from the Sunset and the Richmond, where a ground-floor garage under a flat is begging to become a unit, and from Noe Valley and Bernal Heights, where a rear in-law tucked behind a Victorian needs to thread the setbacks. This is its own City and County, the densest big city in California outside nothing — and the land is worth a fortune. Our designer starts from your actual parcel. Stock makes the family fit the plan. Custom makes the plan fit the lot.
Drawn around a deep skinny SF lot where every foot is fought for
Built into a ground-floor garage or a rear yard behind a Victorian or Edwardian flat
The answer when the lot or the family need is too specific for a shelf plan
The design phase
Design phase, site walk to permit
Custom is won in the drawings, so that's where the hours pile up. It opens with a site walk and a measure-up. In San Francisco the first things I read are the existing structure above and the soil below — most SF ADUs go into a ground floor or a rear yard under a flat, so I'm checking whether the framing above needs a soft-story retrofit and whether you're sitting on Marina or Mission fill. Then concept sketches. You react, we revise. Most clients run three or four rounds before a floor plan feels right; a few push past six. Once the layout locks we move to construction documents: structural sized for seismic design near the San Andreas and Hayward faults, Title-24, mechanical, plumbing, the PG&E load calc. Honest part — this front end runs six to ten weeks before anything reaches SF Planning. Longer than any stock plan. That's the trade.
Site walk reads the structure above and the fill below before a line is drawn
Three to six revision rounds until the floor plan is genuinely right
Construction documents drawn in-house, seismic-engineered, then filed with SF Planning and DBI
Matching the flat
From Sunset stucco to Noe Valley
A custom unit should look like it belongs under your house, not like it got bolted on after the fact. San Francisco makes that genuine work, because the architecture swings hard by neighborhood and a lot of it is protected. Noe Valley, Bernal Heights and parts of the Mission run Victorian and Edwardian flats — period trim, bay windows, cornice detailing that a careless box would insult, and the kind of historic-resource scrutiny that makes SF Planning slow down. The Sunset, the Richmond, the Excelsior and Glen Park lean toward the marina-style stucco rows and tunnel-entrance homes of the 1920s through 40s. We match the parapet line, copy the trim, source siding and stucco texture that read the same from the sidewalk. A garage door swapped for a blank wall fools nobody. A drawn façade keeps the street intact.
Period-correct detailing for Victorian and Edwardian flats in Noe Valley and Bernal
Stucco texture and parapet matching for Sunset, Richmond and Excelsior rows
Façades drawn to survive historic-resource review, not just fill an opening
Multi-gen + finishes
Multi-generational layouts done right
A lot of our SF custom work is families solving one exact problem. Aging parents who want their own front door on the ground floor instead of a flight of stairs. An adult kid who, at San Francisco rents, would rather build in the back than sign another lease. That reshapes the plan. We draw zero-step entries off the sidewalk, 34 to 36-inch doorways, curbless showers with grab-bar blocking already in the walls, and where the footprint allows it, a second primary suite so two generations each keep privacy. The detached state ceiling is 1,200 sq ft, and custom clients push right toward it when the rear yard has the room — though on most SF lots you're working with what the garage or the back gives you. Then finish level. Quartz, real oak floors, a tiled shower instead of a fiberglass insert. Custom designs the premium package in from day one.
“Every ADU we build is designed to add long-term value and open new possibilities for your property. Let's build something great together.”
— Tim, ADU Specialist
Custom Designs
Built to fit your property & needs
Turnkey Process
We handle permits, plans & everything
Built to Last
Quality craftsmanship that stands the test
Financing Made Simple
$0 Down Options. Build Now, Pay Over Time.
You shouldn't have to drain your savings to build wealth. We partner with trusted ADU lenders to find financing that fits — many homeowners build with little to nothing out of pocket.
Home Equity (HELOC)
Tap your existing equity at competitive rates — the most popular way to fund an ADU.
Renovation Loans
Finance the build against your home's projected after-completion value.
ADU-Specific Financing
Specialized lenders who underwrite based on the rental income your ADU will produce.
Cash-Out Refinance
Roll the project into a new mortgage and keep one simple monthly payment.
Estimate Your Monthly Payment
See what financing your ADU could look like — and how rental income can help cover it.
$180,000Loan amount
Credit Score
Very good · 700–739
Estimated Monthly Payment
$1,320/mo
At 7.99% APR over 30 years (illustrative)
Often offset by $2,000–$3,500/mo in rental income
No prepayment penalties with most partners
Pre-qualification with no impact to your credit
Illustrative only — not a loan offer. Actual rates and terms are set by third-party lenders based on your qualifications.
Service areas
Where we build
Headquartered in the Greater Sacramento Area and serving homeowners from the Sierra foothills down through the Bay Area. Don't see your city? We probably still get there — just ask.
The most common things Sacramento homeowners ask before starting an ADU project.
Bay Area ADU economics are a different planet, and I won't soft-pedal it — San Francisco is the priciest market we serve, full stop. For 2025-2026, finished custom detached units here commonly run $450K to $750K or more, depending on size, finish, the seismic and retrofit work, and how brutal the permitting fees land. Call it roughly $480 to $680 a square foot. A garage conversion under a flat can come in lower because the shell already exists, but add a required soft-story retrofit and the number climbs fast. So why does anyone build? Because SF rents and home values are so far above Sacramento that the math still pencils, and because a custom unit solves a one-off lot or family need a stock plan can't reach.
Straight answer: we're a Sacramento-based design-build crew, and San Francisco is about ninety minutes to two hours from our home base. We don't pretend otherwise. We extend out here for homeowners who want our craftsmanship and our value, or for larger custom projects worth the drive. Bay Area pricing carries a lot of slack, and a Sacramento crew that builds to a high standard can deliver real quality without the full local markup. The distance is the honest trade-off, so we say it up front — for a tiny stock unit it rarely pencils, but for a larger custom build worth doing right, the result and the math both hold.
By a wide margin, the ground-floor garage conversion under a flat, and right behind it the rear in-law unit in the back yard. SF lots are tiny and deep, the homes are stacked, and there's almost never room for a freestanding detached unit on a separate pad the way there is in a Sacramento suburb. So the classic SF ADU drops into space that already exists — the garage on the ground floor, or a sliver of rear yard behind a Victorian. Custom matters here precisely because those spaces are odd: low ceilings, an entry tunnel, a sloping back lot, framing above that may need a retrofit. A stock plan assumes a blank pad. Your SF lot rarely gives you one.
Longer than stock, and longer than just about anywhere else we work — that's the honest answer. Design and construction documents run six to ten weeks. SF permitting is among the slowest and strictest anywhere: SF Planning plus DBI, with the chance of discretionary review and historic-resource scrutiny on a Victorian or Edwardian flat. Plan on three to six months at the counter, sometimes longer if a project draws review. The build itself is usually seven to eleven months for a custom unit, with a soft-story retrofit or a tricky rear-yard foundation adding weeks. Door to door you're realistically at fifteen to twenty-four months. The slow City process is the single biggest thing stretching it.
It does, and there's no skipping it in San Francisco. The city sits near the San Andreas and Hayward faults, and large stretches of it — the Marina, SoMa, and the Mission flats — are built on fill that liquefies in a real quake. So the structural engineering on any custom unit is sized for genuine ground movement: heavier shear walls, hold-downs tying framing to the foundation, and a foundation engineered for the actual soil under your lot. On top of that, when you put a unit into the ground floor of an older flat, the building above often needs a soft-story retrofit — the weak open garage level gets braced so the floors above don't pancake. A stock plan ships a generic detail that assumes firm, flat dirt. Custom draws the structure to the ground actually under you.
A soft-story building is the classic SF setup — living floors stacked over a weak open ground level, usually a garage with big door openings and not much wall to resist shaking. In a major quake that bottom level can collapse, so the retrofit braces it with steel frames or new shear walls and ties the structure together. When you convert that ground-floor garage into an ADU, you're already opening up the level that needs the work, so it often makes sense to do the retrofit at the same time. Whether yours is required depends on the building, its age, and any city mandate that applies. We flag it during the site walk, because it's a real line item — better you hear it from me early than discover it mid-permit.
State law caps a detached ADU at 1,200 sq ft, and custom clients push toward that ceiling when the rear yard actually has the room. The honest SF reality is that most lots don't — you're usually shaping the unit to fit a ground-floor garage footprint or a narrow back yard, so the real constraint is the existing structure, not the state number. A garage conversion might land at 500 to 750 sq ft because that's the bay you've got. Where a deep lot gives a real rear yard, we'll draw toward 900 to 1,200 sq ft for a genuine two-bedroom multi-gen unit. Attached and junior ADUs follow different size rules, and we'll run those against your specific parcel.
Yes — that's one of the strongest reasons to go custom in San Francisco. The city is built on hills, so plenty of lots run uphill or downhill off the street, and the back yards behind Glen Park and Bernal Heights homes can drop away fast. A stock rectangle pretends the ground is flat. Our designer works the unit into the real grade: stepped or pier footings that hold it level, an entry sequence that lands where the street actually meets the lot, drainage drawn so water runs away from both structures. Same with a mature tree, a light well, or a weirdly angled lot line. On a high-value SF parcel that kind of fit is the difference between a unit that works and one that crowds everything around it.
San Francisco is a combined City and County, so there's no separate county to deal with — everything routes through SF Planning and the Department of Building Inspection, DBI. And yes, it really is that strict. Among the slowest, most expensive, most scrutinized processes anywhere. The state ADU law is meant to streamline approval, but SF still layers on the chance of discretionary review and serious historic-resource review on the Victorian and Edwardian housing stock. Fees are high. The counter is busy. We file a complete, seismic-engineered set precisely so a tough reviewer has less to push back on, and we build the slow timeline into the plan from day one rather than acting surprised by it.
For the right reasons, yes — even from ninety minutes away. SF has some of the highest rents and home values in the country, so an extra legal unit carries real worth the day it's finished, whether that's housing parents, an adult kid priced out of the market, or rental income that pencils far better than it would in Sacramento. The honest caveats are the price, the brutally slow strict permitting through Planning and DBI, and the seismic and soft-story work on older flats — none of which make custom cheap or fast. But if you've got a deep skinny lot, a garage to convert, a flat to match, or a specific family need, custom is the only path that actually solves it.
Other services
Not quite the right fit?
Every Sacramento ADU project is different. Here are the other paths we build under one roof — and we're happy to talk through which one fits your lot best.
We treat every home like it's our own — quality work, clear communication, and happy homeowners.
PaulOwner · Future Generation
9 min read1,909 words7 sections
Custom ADU design and construction in San Francisco
Some San Francisco lots just won't take a stock plan. A ground-floor garage under a Sunset flat begging to become a unit, a Victorian in Noe Valley with a rear yard that drops away, a family with parents moving in who need a zero-step unit drawn around them — that's when you build custom. We're a Sacramento design-build crew about ninety minutes to two hours east (CA license #1119373) that draws a bespoke ADU for your exact SF parcel and builds it, design through final inspection. Call (916) 677-9774.
01Section
What actually makes an ADU custom
People throw "custom" around loosely, so let me draw the line. A stock ADU is a plan we've already drawn — pick a size, swap a finish, drop it on a pad. Quickest, cheapest route. Trouble is, San Francisco almost never gives you a pad. The lots are deep and narrow, the homes are stacked, and the space for a new unit is usually a ground-floor garage or a sliver of rear yard. That's already not a stock situation.
Custom means the design starts at zero, on your parcel. Our designer takes the survey, the SF Planning setbacks, the soil report, the existing structure above, and how your family actually plans to live — then draws a unit that didn't exist until your lot called for it. The footprint bends to the garage bay or the back yard. The foundation answers the fill. The façade answers your flat.
