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Fremont · Custom ADU
A Fremont ADU drawn for your lot, your family, and the fault under it.
Fremont gives you more lot than San Francisco ever will — we draw a bespoke unit around your slope, your trees, and the Hayward Fault, then build it end to end.
Trusted by homeowners across Sacramento & surrounding areas.
Custom ADU in Fremont — fast facts
City
Fremont
ADU type
Custom ADU
Contractor license
CSLB #1119373
Free estimate
(916) 677-9774
Last updated
Why custom in Fremont
When the lot needs its own plan
A stock detached plan wants a flat, empty rectangle and quiet dirt. Fremont gives you more room to work with than San Francisco or Oakland — but more room isn't the same as a blank pad. The city was stitched from five old districts, so a Mission San Jose lot climbing toward the hills behaves nothing like a flat Centerville parcel on bay clay. Add mature trees, the occasional pool, an Alquist-Priolo fault zone up the slope, and a catalog footprint runs out of answers fast. Custom starts where a pre-drawn plan can't reach. We draw the unit to the buildable area you actually have, to the grade, to the seismic engineering, and to the house already standing — then we build it.
Foundations engineered to the grade and the Hayward Fault, not a generic slab
Drawn to fit a real Fremont lot from the first line, district by district
The answer when no off-the-shelf footprint lands on the parcel
The design phase
Site walk to permit, drawn in-house
Custom is won in the drawings, so we put real hours there. It opens with a site walk and a measure-up — and on a Fremont lot, before anyone knows how the grade or the access actually behaves. A survey leaves things out. It won't tell you how a Mission San Jose lot steepens behind the house, where the mature trees on a Niles parcel pin the footprint, or how tight the materials path is down a side yard. That first visit reshapes the plan more often than not, and up the hill it points the foundation engineer at a soil report early. Then concept sketches. You react, we revise. Most clients run two or three rounds; a few push past five. When the layout locks we draw full construction documents and file with the City of Fremont. The honest part: this front end runs six to ten weeks before the counter even opens it.
Site walk and access study before a single line gets drawn
Soil report drives a hill foundation from day one
Full construction documents drawn in-house, then filed with the city
Matching the main house
Matching a Fremont ranch or tract home
A custom unit should look like it grew out of your house, not like it got dropped behind it. Fremont makes that specific, because the housing stock shifts as you cross districts. Centerville, Irvington, and Warm Springs run heavy to mid-century ranch — low rooflines, wide eaves, long horizontal lines, often a clinker-brick or board-and-batten accent. Newer tracts toward the Tesla corridor read taller and tighter. Drop a generic two-story box behind a single-story ranch and it fights the whole property. So we pull roof pitch off your actual house, match the eave depth, carry the siding profile across, and keep the new unit's massing in scale with what's there. A copied stock elevation rarely belongs on an Irvington ranch lot. A drawn one does — and it appraises like it.
Low ranch rooflines and wide eaves for Centerville and Irvington
Scale and massing kept in step with newer Warm Springs tracts
Roof pitch, eave depth and siding drawn to your specific home
Multi-gen + finishes
Multi-generational layouts done right
A lot of our Fremont custom work is families solving one exact problem — aging parents who want their own front door, or adult kids who looked at Bay Area rent and decided the backyard beats a lease. The rent math out here is a different planet from Sacramento, which is exactly why these units pencil. That reshapes the plan. We draw zero-step entries, 36-inch doorways, curbless showers with grab-bar blocking set in the walls, and a second primary suite so two generations each keep their own privacy. The detached state ceiling is 1,200 sq ft, and custom clients tend to push right up against it — at that size you fit two real bedrooms, a full kitchen, and a proper living room. Then finish level: quartz, real oak floors, a tiled shower instead of a fiberglass insert. Custom is where the premium package gets drawn in from day one, not bolted on later.
“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.
Custom is the priciest path, and the Bay Area pushes it higher than almost anywhere we work — I won't soft-pedal it. For 2025-2026 we're seeing finished custom detached units in Fremont land roughly $412K to $755K-plus depending on size, finish level, and how rough the site is. The ground is the big variable. A Mission San Jose hill lot needs a stepped or pier-and-grade-beam foundation cut into the slope; the flats are bay clay, which carries its own engineering before you frame a wall. Then there's the seismic detailing the whole region requires near the Hayward Fault, plus Fremont's high permit fees and slower review. The flip side is why owners build here anyway: Fremont rents, propped up by Tesla and the tech corridor, run far above Sacramento. Even a $600K-plus unit pencils out in a way it never would back home.
Fair question, and I'll be straight: we're based in Sacramento, about 75 minutes from Fremont. We're not the closest crew you can hire. We extend out here for homeowners who want our craftsmanship and our pricing over a Bay Area outfit's quote, or for a larger custom project that's worth the roughly two-hour round trip — and custom usually is, because the value sits in the design and the build quality, not in being five minutes away. I'll be on your lot for the site walk and for the foundation pour, the framing, and the key inspections. If your job is a small, simple unit on a flat Centerville lot, a Fremont-local crew may serve you better, and I'll say so. For a complex hill build, the right team beats the close one.
A stock plan is pre-drawn and repeated — faster and cheaper, because the design work is done and it drops onto a flat pad. Custom starts at zero for your parcel: our designer sizes and shapes the unit around the grade, the trees, the seismic engineering, the look of your Fremont home, and exactly how the family plans to live in it. Custom costs more and takes longer up front. The reason to choose it is a one-off problem — a steep Mission hills lot, a pool or mature oaks in the way, a ranch main house you want matched, an accessible suite for a parent — that a rectangle off the shelf can't reach. If your lot were flat and clear and your house ordinary, we'd happily steer you to stock and save you money. In Fremont's older districts, that's rarer than you'd think.
Longer than stock — that's the honest answer, and Fremont's permitting is slower than the Sacramento suburbs we usually work in. Design and construction documents run six to ten weeks. City of Fremont review on a clean set often runs ten to sixteen weeks, longer if the lot sits in an Alquist-Priolo fault zone that pulls in geotechnical scrutiny. The build itself is usually seven to ten months for a custom detached unit, with a hillside foundation stretching it. Door to door you're looking at roughly thirteen to nineteen months. The slower city counter, the fault-zone review, and the hill engineering are what stretch it past a flat-lot Sacramento job — plan for it from the start rather than getting surprised at month four.
It can, and on a custom job it's worth getting ahead of. The Hayward Fault and an Alquist-Priolo fault zone run along the Mission hills, where the lots steepen. If your parcel sits inside that zone, the city requires a geotechnical study before it'll approve a habitable structure, and that report drives both the foundation and the timeline. The upside of custom here is real: because we're drawing from scratch, we design the unit and its foundation to the soil report instead of forcing a flat-pad plan onto ground that won't take it. We check the fault-zone maps and any pool, trees, or grade issues on the first visit, then draw the set to clear review rather than fight it. A catalog plan has no answer for a fault-zone hillside. A drawn one does.
That's exactly where custom earns its keep here. A flat-pad stock plan has nothing to offer a Mission San Jose or upper-hills lot that drops away behind the house. We start with a grade analysis and a soil report, then design a hillside foundation — often a stepped foundation or pier-and-grade-beam, where drilled piers reach down to stable material and grade beams tie them together so the unit sits level on a slope that doesn't. The structure gets engineered for the lateral loads a hill imposes on top of the seismic loads the Hayward Fault demands. It costs more than a flat slab; no way around that. It's also the only thing that puts a real, safe, level unit on a lot a catalog rectangle can't touch. On a Fremont hillside, custom isn't an upgrade — it's the path that works.
Heavily, and it should. The Hayward Fault runs along the base of the Mission hills and through the East Bay, and it's considered one of the likeliest faults in the state to produce a major quake. Building here means building for that. On every custom unit we draw the shear walls, hold-downs, anchor bolting, and a foundation tied together so the structure rides a shake instead of coming apart in one. On a flat lot that's a well-detailed slab on grade — though Fremont's bay clay still needs engineering attention. Up the hill it compounds with the slope loads, which is part of why those foundations are built the way they are. A stock plan drawn for a calm, flat site elsewhere doesn't carry this detailing. A custom set drawn for a Fremont parcel builds it into the structural drawings from the start.
The permit goes through the City of Fremont — it's its own incorporated city, so plan check and inspections run through the city's building and planning departments. One counter, high fees, slower review than the Sacramento suburbs. Power is PG&E. A custom unit's electrical service, any main-panel upgrade, the load calc, and the meter set all coordinate through PG&E, which in the Bay Area can be slow. An all-electric unit with a heat pump, an induction range, and maybe an EV charger pulls real load, so we size the service and line up PG&E early in design rather than at the end, where it stalls a final inspection. With the city counter already slow, getting the utility piece moving early is half of keeping a custom build on schedule.
State law caps a detached ADU at 1,200 sq ft, and most of our custom clients build right up near that ceiling — at 1,100 to 1,200 sq ft you fit two genuine bedrooms, a full kitchen, and a real living room, which is usually the whole point of going custom. Whether your Fremont lot has room to site a unit that size depends on the parcel, and this is where the city's spread-out layout helps: a Centerville or Irvington backyard often has more usable depth than you'd get in San Francisco or Oakland. A steep Mission San Jose hill lot is tighter, since the buildable area gets carved out of a slope and the setbacks bite. Smaller is allowed; we just rarely see custom clients want it. Attached ADUs follow a different size rule tied to the main house, so we'll run those numbers for your specific lot.
In-house. Our designer does concept, floor plans, elevations, and the full construction document set, and that same drawing carries straight into the build with no handoff gap. You're not coordinating a separate architect, a separate geotechnical engineer, and a separate builder who all point fingers when the slope shifts or the fault-zone comments come back. One team owns the design and owns the result — which matters even more on a Fremont custom job, where the field decisions on a hill foundation and the back-and-forth with a slower city counter are constant, and someone needs to own them end to end.
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 read1,948 words8 sections
Custom ADU design and construction in Fremont
Some Fremont backyards just won't take a stock plan. A Mission San Jose lot that climbs away behind the house, a Niles parcel with oaks the city won't let you cut, a ranch home you want the new unit to match, or parents moving in who need a place drawn around them — that's when you build custom. We're a Sacramento design-build crew (CA license #1119373) that extends to Fremont for owners who want our craftsmanship and value, draws a bespoke ADU for your exact lot, and builds it design through final inspection, one team the whole way. Call (916) 677-9774.
01Section
What actually makes an ADU custom
People throw "custom" around loosely, so let me draw the line. A stock or model ADU is a plan we've already drawn and built before — pick a size, maybe swap a finish, and it drops onto a flat pad. Quickest, cheapest, and for a clean Fremont backyard with stable dirt and an ordinary main house, often the right one. We build those gladly. But it isn't custom.
Custom means the design starts at zero, on your parcel. Our designer takes the survey, the City of Fremont setbacks, the soil report, the grade, the seismic requirements, and how your family plans to live. Then a unit gets drawn that didn't exist until your lot called for it. The footprint bends to the buildable area. The foundation answers the slope and the fault. The roofline answers your house.
