CA License #1119373Licensed, Bonded & InsuredPowered by Future Generation ConstructionFuture Generation
San Jose · Detached ADU
A standalone backyard home for your San Jose lot.
Its own foundation, its own roof, its own front door — a true detached ADU in San Jose, drawn and built by a Sacramento crew that drives the two hours because Bay Area homeowners ask us to.
Trusted by homeowners across Sacramento & surrounding areas.
Detached ADU in San Jose — fast facts
City
San Jose
ADU type
Detached ADU
Contractor license
CSLB #1119373
Free estimate
(916) 677-9774
Last updated
Freestanding, shares nothing
A detached unit is its own building
What makes a detached ADU worth the money is also what makes it the harder job: it shares nothing structural with your house. Its own slab. Its own walls. Its own roof. On a Willow Glen lot we set a 612 sq ft single-story cottage behind one of those charming older bungalows, and because the unit stood completely free we swung the living-room glass toward the afternoon light instead of staring at a six-foot fence. That's the freedom detached buys you. The cost of that freedom is a second foundation, a separate roof system, and a long materials path from a tight street to the back of the yard. We map every foot of it before you sign anything.
Independent foundation, framing, roof and exterior envelope
Oriented to your actual San Jose lot, not a fixed pad
No shared wall means fewer fire-separation headaches than attached
City of San Jose permitting
The San Jose detached-ADU permit path
Let me be straight about who we are first. We're a Sacramento-based design-build crew, and we extend to San Jose for homeowners who want our craftsmanship and value, or for projects big enough to justify the drive. Your permit runs through the City of San Jose — Planning, Building and Code Enforcement, not Santa Clara County. State law made the ADU review ministerial, so a complete, code-compliant set has to get issued. That's leverage, and we use it. But San Jose is honestly one of the stricter, slower counters in the state, with high fees, so we submit a thick package the first time — site plan, structural, Title-24, MEP, seismic — and skip the correction loops that eat months here.
Reviewed by City of San Jose Planning, Building & Code Enforcement
Complete plan set drawn in-house to cut correction rounds
Ministerial ADU review under state law: a clean set must be issued
Seismic, access + PG&E
Tight lots, faults, and getting in
Here's the Bay Area reality nobody sugarcoats. San Jose sits between the Calaveras and Hayward fault systems, so a detached unit needs real seismic design — shear walls, hold-downs, anchored framing — and the City reviews it hard. Lots here are tight and land is worth a fortune, so the materials path matters more than anywhere in our Sacramento work: everything that builds a backyard unit has to physically reach the back of a narrow lot. We measure gate width, side-yard clearance and overhead lines on the first visit. Up toward Almaden Valley and Evergreen some lots run uphill into the foothills, which adds retaining and grading. And power is PG&E here — the service drop, panel and meter all run through PG&E's process, which we open early.
Seismic engineering for the Calaveras and Hayward fault zones
Side-yard, gate and overhead-line clearance measured first visit
PG&E service, panel and meter coordination started early
What the number actually is
What a detached ADU costs in San Jose
I'll give you a range, then tell you why San Jose ranges look insane to anyone from Sacramento. Bay Area ADU economics are a different planet. A detached unit here commonly runs $400K to $700K-plus all-in — driven by land value, City fees, seismic design and the cost of working a tight Silicon Valley lot. That number stops a lot of people cold. But the math still works, because San Jose rents and home prices are so much higher than ours that the unit pays for itself far faster than the same build in Elk Grove would. The honest caveat: detached carries its own foundation and roof, so it never pencils cheaper than a garage conversion. If raw budget is the only driver, convert. If you want a real freestanding home that throws off Bay Area rent, detached wins.
Fixed-price proposal after a free in-person San Jose site visit
Detached runs above a garage conversion — second foundation and roof
High Bay Area rents are what make the steeper number pencil
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From design to move-in, we handle everything. Transparent pricing, on-time delivery, and uncompromising quality.
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Trusted by homeowners across Sacramento & surrounding areas.
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“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.
Through the City of San Jose — its Planning, Building and Code Enforcement department handles plan check, the building permit and issuance. San Jose is an incorporated city, the largest in the Bay Area, so you're not dealing with Santa Clara County for a parcel inside city limits. The City has its own ADU submittal checklist, its own portal, and its own fee schedule — and that schedule is steep compared to what we see around Sacramento. We confirm your lot sits inside San Jose city limits and pull the exact current checklist before we draw a single sheet, because submitting to the wrong agency or against an old checklist quietly costs weeks here.
Honest answer: because homeowners ask us to. We're a Sacramento-based design-build crew, and San Jose is about a two-hour drive from our home base. We extend there for owners who want our craftsmanship and our pricing, or for projects large enough that the drive is worth it. We're upfront that we're not a corner-shop local outfit camped in Cambrian — we're a traveling crew that runs a tight, fully-drawn project. For a lot of Bay Area owners that's a feature: they get a real builder who isn't carrying Silicon Valley overhead. For a small, simple job a local might make more sense, and we'll tell you that.
Yes. San Jose is PG&E territory, so the service drop, any panel upgrade, and the new meter for your detached ADU all run through PG&E's application process — which has its own rules and a timeline that does not move fast. Water and sewer go through San Jose's municipal utilities. If your main panel is near capacity, which is common on older homes in Naglee Park or the Rose Garden, you're often looking at a meaningful upgrade before the unit can be energized. We open the PG&E request early so a meter isn't the one thing holding up your final after everything else is finished.
Because everything underneath it costs more here. Land value, City of San Jose fees, seismic engineering for the fault zones, and the labor of working a tight lot all stack up. A detached unit is a full ground-up build — its own foundation, framing, roof and utilities — so there's no shortcut on materials or structure. Bay Area ADU economics genuinely are a different planet from Sacramento's, where the same unit might run half as much. The reason owners still do it is rent: San Jose rents and home values are high enough that the unit earns its cost back far faster than it would in the Central Valley.
Yes, and the City reviews it carefully. San Jose sits between the Calaveras and Hayward fault systems, so a freestanding ADU gets engineered for real seismic load — shear walls, hold-downs, anchor bolts, and a foundation detailed for ground movement. This is one area where San Jose's stricter plan check actually protects you. We bring structural engineering into the design from the start rather than bolting it on at the end, because a detached unit's lateral system has to be drawn into the framing, not patched over it. It adds cost versus a flat Sacramento lot, and it's not optional here.
Usually, but the lot tells us a lot before we promise anything. San Jose lots run tight and land is expensive, so siting the unit, keeping setbacks, and finding a materials path to the backyard is half the design work. We measure side-yard width, gate clearance and overhead lines on the first visit. In neighborhoods like Willow Glen or the Berryessa area we've threaded units onto lots that looked too small until you actually plan the access. Where a yard is genuinely too narrow for a freestanding build, we'll say so and talk about an attached unit or a garage conversion instead of forcing a detached that doesn't fit.
Plan for longer than Sacramento. The City of San Jose's review is among the slower and stricter in the state, so even a complete set can sit in plan check longer than we'd see at home, and the fees are higher. Realistically, signed contract through permit-in-hand often runs several months once you fold in design, seismic engineering and PG&E coordination. Construction on a detached unit then runs its own calendar on top. The biggest variable is submittal quality — a thin set triggers correction cycles, and correction rounds in San Jose burn more weeks than the build itself sometimes. We submit thick to avoid them.
Depends on what you want and what your lot allows. Detached is the most flexible path — you orient the unit for light and privacy, size it to the yard, and it shares nothing with your house. But it's a full ground-up build, so it costs more than converting an existing garage that already has a slab and roof. If your San Jose budget is tight and you have a usable garage, conversion almost always pencils cheaper. If you want a genuine second home in the backyard that commands top Bay Area rent, detached is worth the premium. On the first visit we'll look at both and give you real numbers, not a sales pitch.
Across the city — Willow Glen, the Rose Garden, Naglee Park, Cambrian, Almaden Valley, Evergreen, Berryessa, Santa Teresa and the downtown fringe. Each one behaves a little differently. Willow Glen and the Rose Garden have older bungalows where the new unit has to read right against established homes. Almaden Valley and Evergreen run toward the foothills, so some lots slope and need retaining and grading. Downtown and Naglee Park lots are tight and older, which means careful access planning. We don't have a single template — we design the detached unit to the specific block, setbacks and grade of your parcel.
A detached ADU is far enough from the house that you typically run separate utility lines to it — water, sewer, gas and a dedicated electrical feed from a panel PG&E meters. That trenching across the yard is part of why detached costs more than an attached unit sharing the main house's systems. The upside is independence: separate metering or sub-metering makes the unit clean to rent and clean to track. We design the utility runs into the site plan from day one and coordinate the PG&E service and San Jose's water and sewer connections so nothing's improvised in the field. On a tight lot, where those trenches go matters as much as where the building sits.
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 read1,894 words7 sections
Building a Detached ADU in San Jose — How a Sacramento Crew Approaches a Bay Area Backyard Build
A detached ADU is a standalone home in your backyard — its own foundation, its own roof, its own walls, fully independent of the main house. We're Future Generation Construction, a Sacramento-based design-build outfit, and we drive the two hours to San Jose for homeowners who want our craftsmanship at our pricing. This is the long version: what detached means on a tight Silicon Valley lot, how the City of San Jose runs permits, why the numbers look the way they do, and where the honest tradeoffs are.
01Section
What detached actually means here
A detached ADU shares nothing structural with your house. That's the whole definition, and it's worth sitting with, because it drives every decision downstream. Your existing home keeps its foundation, its roof, its walls. The new unit gets its own of each. They stand as two separate buildings on one San Jose lot, connected only by the utility lines we trench between them and the path you walk across the yard.
That independence is why detached is the most flexible ADU you can build. We're not bound by where your garage sits or which wall we can lean against. On a Willow Glen lot we can rotate the unit to catch afternoon light, push the entry away from the main house for privacy, or step it back from a slope toward Almaden Valley. You pick the orientation, the windows, the relationship to the yard — within setbacks — because nothing is fixed by the existing structure.
