Building an ADU in San Jose: What to Expect

San Jose’s housing costs make an ADU one of the smartest moves a homeowner can make, and almost every family who calls us asks some version of the same question: what actually happens between “we’re interested” and “we’re moved in”? Here’s the honest, step by step answer, built around the process we use for every home we build across the city, from Willow Glen to Berryessa.

The short version: we analyze your property, you tour our factory, we visit your lot in person, we run a feasibility study, we review the findings together, you lock in your customizations, and then we build your home off site while your yard stays untouched and crane it into place. San Jose’s ADU rules are ministerial, meaning the city has to approve or deny a complete application within 60 days with no public hearing, so the permitting side of this moves faster here than in a lot of California cities.

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Step 1: Property analysis comes first

Before anyone drives out to your home, we take a first pass at your lot using what you tell us and public property records: lot size, setbacks, existing structures, and what kind of ADU is realistic given San Jose’s zoning. Because California requires every city to allow at least an 800 square foot, 16 foot tall ADU with 4 foot side and rear setbacks no matter what, we can usually tell you within a conversation whether you have room for a bigger model or should plan around the guaranteed minimum.

Step 2: Factory tour

Next, you see where your home actually gets built. Walking our factory floor in Salinas is the step that turns “prefab ADU” from an abstract idea into something concrete: you see the framing, the finishes, and the same construction line every one of our 14 models comes down. It also gives us a chance to talk through layouts and budget in person before anything is finalized.

Step 3: The site visit, about 50 minutes from our factory door

San Jose sits roughly 50 minutes from our Salinas factory, close enough that a site visit is a normal part of the process rather than a special trip. Our team walks the actual lot, confirms access for delivery and crane placement, checks utility hookups, and looks at anything the property records alone would not show us. This is also where local specifics like San Jose’s own zoning code (the city has adopted state ADU law directly, so what applies statewide applies here) get confirmed against your real property.

Step 4: The feasibility study

Once we’ve seen your lot, we run a formal feasibility study: $497 for most properties, or $997 if the lot is empty with no existing structure to reference. That fee credits toward your build if you move forward, and it’s refundable only if your property genuinely cannot host an ADU. This is where we finalize setbacks, height limits, parking (most San Jose lots qualify for a parking exemption under state law, whether that’s proximity to transit, a garage conversion, or another exemption), and which of our models actually fit.

Step 5: Reviewing the findings together

We sit down and walk through what the feasibility study found, model by model if needed. This is also where fees get real: San Jose waives school and parkland impact fees for any ADU under 750 square feet, and applies them once you cross that line, with building permit fees scaling to the size of the ADU. Six of our models (the Four Fifty, The 405, Five Five Five, Six Sixty, Six Sixty 2BR, and Seven Forty-Nine) stay under that 750 square foot threshold and skip those local impact fees entirely.

Step 6: Confirming your customizations

With the numbers on the table, you pick your model and lock in finishes. A single homeowner adding a rental unit might land on the Six Sixty 2BR (660 sqft, 2 bedroom, 1 bath, $339,000, about 5 months to build), while a family wanting more room for a parent or adult child often looks at the Nine Forty-Five 3/1 (945 sqft, 3 bedroom, 1 bath, $445,000, about 6 months) or the full Twelve Hundred at 1,200 sqft for $549,000. Every model is all inclusive, permits through appliances, so the number you’re quoted is the number you plan around.

Step 7: Build and deliver

Your home gets built inside our factory while your San Jose lot stays undisturbed, then it’s delivered by crane and finished on site. Overall project timing still depends on permitting, which is the one step nobody, including us, fully controls, but San Jose’s first round of building plan review typically runs about 20 business days, well inside the state’s 60 day ministerial clock.

What this looks like across San Jose

We’ve delivered finished homes in neighborhoods across the city, and the reasons vary as much as the addresses. Some homeowners are adding a rental unit to help with the mortgage using San Jose’s rent benchmarks (roughly $2,500 a month for a 1 bedroom, $2,950 for a 2 bedroom) as a planning guide. Others want space for aging parents or adult kids. A few are thinking further ahead: San Jose allows ADU condominium conversions, so once a condo map is approved, an existing ADU can be sold separately from the main home, which is worth knowing if you’re building with resale flexibility in mind. The city’s own materials also note that a legally built San Jose home can be eligible for up to three ADUs on one property, and that preapproved ADU plan sets along with the city’s ADU Ally desk are available as local resources that can shorten plan review.

San Jose’s permitting timeline, in plain terms

Because San Jose applies state ADU law directly rather than layering on its own restrictions, the rules are the same ones that apply everywhere in California: no owner occupancy requirement for a standard ADU, no public hearing, and a hard 60 day deadline for the city to act on a complete application. For a deeper walkthrough of the permit process itself, see our ADU permits in San Jose guide, and for a full breakdown of how the schedule plays out start to finish, see ADU timeline in San Jose.

Paying for it

The $1,000 signup deposit is refundable if your financing falls through, and the feasibility study fee credits toward your build. Most San Jose homeowners we work with use a HELOC, a cash out refinance, or a construction loan against their home equity; we don’t lend directly, so we point people toward resources like How to Finance an ADU in California, HELOC vs Construction Loan for an ADU, and ADU Loans California to compare options before committing. If you’re running rental numbers, remember that a typical net cash flow estimate factors in 5% vacancy, 8% maintenance, 1.25% property tax, and 0.5% insurance on the ADU’s cost each year; these are planning estimates, not guarantees, but they’re a reasonable starting point for a San Jose rental unit.

Frequently asked questions

How long does building an ADU in San Jose actually take?

It depends on the model you choose. Our smaller homes like the Four Fifty run about 4 months to build, while larger models like the Twelve Hundred run 7 to 9 months. On top of build time, San Jose’s first round of plan review typically takes about 20 business days, inside the state’s 60 day ministerial approval window, though overall project timing still depends on how permitting goes.

Does San Jose require a public hearing or neighbor approval?

No. ADU approval in San Jose is ministerial under California law, meaning the city has to approve or deny a complete application within 60 days without a public hearing or neighbor sign off.

Do I need to live on the property to build an ADU in San Jose?

No, owner occupancy is not required for a standard ADU, and cities cannot require it. It only comes into play with a Junior ADU (a unit built within the walls of the main home, up to 500 sqft) if that JADU shares a bathroom with the main house.

Can I sell my ADU separately from my main home in San Jose?

San Jose does allow ADU condominium conversions, so an existing ADU can be sold separately from the primary home once a condo map is approved. It’s a detail worth factoring in if resale flexibility matters to you.

Ready to see what your San Jose property can hold

Every San Jose project starts the same way: a conversation about your lot, your budget, and what you’re actually trying to build toward. Our team can walk you through the property analysis step and get a feasibility study on the calendar. Reach out and let’s figure out what fits.