Attached Garage Conversion in San Jose, CA
Attached garage conversion in San Jose typically runs $120,000 to $200,000 for a complete 400-square-foot ADU with kitchen and bath, and most projects take 4 to 7 months from design to final inspection. We’re Lodgewick ADU San Jose, part of the Kingswell family of home-service companies, and we’ve been converting attached garages into livable space since 2010. If you’re weighing this against a detached build, you’ll want to read our full Garage Conversion ADU in San Jose page first, then come back here for the attached-specific details.
An attached garage conversion means exactly what it sounds like: the garage shares at least one wall with your main house, and we convert that existing footprint into a self-contained accessory dwelling unit, or ADU, which is a legal secondary home on your lot. Because the structure already exists, you skip foundation work and shell construction costs. That’s usually $40,000 to $70,000 less than building a detached ADU of the same size. Call (669) 266-4319 and we’ll walk you through what’s realistic for your specific garage.
Key Takeaways
- Attached garage conversions cost $120K-$200K in San Jose, depending on finish level and existing condition
- Most projects take 4 to 7 months from design through final inspection
- Written price before any work starts, on every project, no exceptions
- The 365-Day Done Right Promise means we come back and fix it if it’s not right
- A live person answers our phones 24/7, including weekends and holidays
When You Need an Attached Garage Conversion
You don’t need a conversion just because the garage is messy. You need it when the space has stopped earning its keep and you’re ready to make it livable. Here’s what we hear from homeowners in San Jose neighborhoods like Willow Glen, Cambrian, and Berryessa:
- Your parents are moving in, and stairs are a problem. An attached conversion gives them a ground-floor suite with no stair access issues, and the shared wall means they’re close enough to check on without sharing a bathroom.
- You’re paying San Jose rent prices for storage. If the garage holds boxes you haven’t opened since 2016, that’s the most expensive storage unit in the county. Convert it and you get rental income or a guest suite instead.
- You need home-office separation that actually separates. Working from the dining table doesn’t work when the dining table is also where dinner happens. A converted attached garage gives you a room with a door that closes, wired for what a real office needs.
- Your adult child can’t afford San Jose rent. An attached garage ADU keeps them on the property with privacy on both sides, and they’re still close enough to borrow the car.
- You want rental income without giving up your whole backyard. Detached ADUs eat yard space. An attached conversion uses the footprint you already have.
- The garage door is dead and the slab has cracked. If you’re looking at a new door, new framing, and new drywall anyway, the incremental cost of making it livable gets a lot smaller.
Within San Jose, attached conversions also tend to move through the city’s permitting process a little faster than detached builds because you’re working inside an existing structure. That said, the city still requires a full plan set, Title 24 energy compliance, and a final inspection before anyone can legally live in the space. We handle all of that, and the permit status is part of the written scope you’ll see before work starts.
Our Attached Garage Conversion Process
We work the same way on every project, and it follows The Kingswell Way: say the price before the work, show up in the window given, leave the place cleaner than found, put the guarantee in writing, come back if it fails. Here’s how an attached garage conversion with us actually goes.
- Site visit and feasibility check. We measure the garage, check the foundation slab, look at the roof connection to the main house, and assess the electrical service. Within a week you get a written price for the work scope we’re proposing, not a verbal estimate that can drift.
- Design and permitting. We draw the plans, work through San Jose’s ADU checklist, and submit the permit package. If you’re interested in prefab components from companies we know well like Plant Prefab or Abodu, we’ll spec them here so the permit set matches what actually gets installed.
- Demolition and structural prep. The garage door comes out, the opening gets framed and sheathed, and we address whatever the slab needs. If we find dry rot or termite damage where the garage meets the house, we fix it and document it. No surprises billing, no “we’ll figure it out later.”
- Framing, MEP, and drywall. New interior walls go up, electricians pull the circuits, plumbers run supply and drain lines for the bath and kitchen. This is the phase where you’ll actually see the ADU take shape.
- Finishes and fixtures. Flooring, cabinetry, tile, paint, trim, doors, and the appliances. If we’re using James Hardie siding products on the exterior wall that replaced the garage door, that’s installed here.
- Final inspection and walkthrough. The city signs off, we walk the space with you, and you get the written guarantee. If anything isn’t right within the first year, we come back and fix it as part of the 365-Day Done Right Promise.
Attached Garage Conversion Pricing in San Jose
Here are the real numbers, because you should never have to call just to get a ballpark. These ranges reflect what we’ve seen on attached garage conversions in San Jose over the last several years, including permits, labor, and materials.
| Scope | Price Range | What’s Included |
|---|---|---|
| Basic studio conversion (300-400 sq ft) | $120,000 – $150,000 | One living space, small kitchenette, full bath, basic finishes |
| One-bedroom ADU (400-500 sq ft) | $150,000 – $180,000 | Separate bedroom, full kitchen, full bath, mid-range finishes |
| Two-bedroom ADU (500-600 sq ft) | $180,000 – $220,000 | Two bedrooms, full kitchen, full bath, upgraded finishes |
| Prefab or panelized attached ADU | $140,000 – $190,000 | Factory-built components from Abodu or Plant Prefab, site work included |
What drives the price up or down on an attached garage conversion in San Jose specifically:
- Foundation condition. Older homes in areas like Rose Garden or Naglee Park often have slabs that were poured thin and never intended for living space. If we need to reinforce or repour, that’s $8,000 to $20,000 depending on what we find.
- Electrical service upgrades. Adding a second dwelling unit on an attached structure usually means a new subpanel, and sometimes a main panel upgrade. A 200-amp service upgrade in San Jose runs $3,500 to $6,000 on top of the conversion.
- Bathroom placement. Sewer lines in San Jose homes don’t always run where you’d want the bathroom. If we’re trenching across the existing garage slab or running new drain lines around the outside, expect $5,000 to $12,000 more.
- Finish level. Stock cabinets, laminate counters, and basic tile will keep you near the bottom of the range. Custom cabinetry, quartz, and upgraded flooring push you up.
- Roof tie-in work. Attached garages share a roof line with the house, and sometimes that connection needs flashing, re-sheathing, or insulation work that a detached build wouldn’t require.
Every project gets the same treatment on price: a written number before work starts, no exceptions, no price changes at the door. Call (669) 266-4319 and we’ll send someone out to measure and give you the written price within about a week. Estimates are free.
Why the Attached Garage Makes Sense in San Jose Specifically
San Jose’s ADU rules changed a lot in 2020 when the state streamlined ADU permitting, and again in 2023 when the city updated its accessory dwelling unit ordinance to align with state law. Attached conversions benefit from the same relaxed setbacks and parking requirements as detached ADUs under state law, which means we can usually keep the conversion within the existing footprint without triggering variance hearings or neighborhood review. In older San Jose neighborhoods where lot coverage is already maxed out, the attached garage conversion is often the only legal path to adding square footage.
There’s also the climate piece. San Jose gets real heat in the summer, and attached garages often share an insulated wall or two with the main house. That shared thermal envelope means lower heating and cooling costs than a detached unit sitting out in the yard. We’ve done conversions in Evergreen and Almaden Valley where the homeowner’s summer energy bill for the ADU alone was under $60 a month because the attached wall did half the work.
One more San Jose-specific thing: the city collects park impact fees on new ADUs, but attached conversions of existing garage space are sometimes exempt or partially exempt depending on the square footage and whether any new foundation is poured. We’ll tell you exactly what your fees look like during the feasibility check, and that number goes in the written price too.
What We Actually Do Differently
Every contractor says they do good work. The question is what happens when the work isn’t good. Here’s what we commit to in writing on every attached garage conversion:
- The 365-Day Done Right Promise. If it’s not done right, we make it right. That’s in writing on every project, and it includes a free return visit if the work fails within the guarantee period. You don’t have to chase anyone down.
- Written price before any work starts. Not a range, not a verbal estimate, not a “we’ll see how it goes.” The number is on paper before a single nail is driven, and it doesn’t change at the door.
- Background-checked, uniformed technicians. You’ll always know who’s on your property. Every person who shows up at your San Jose home is employed by us, background-checked, and wearing a Lodgewick uniform.
- A live person answers the phone, 24/7. Not a voicemail loop, not a chatbot. Call at 2 p.m. or 2 a.m. and you get a human who can answer questions about your project.
- Real brand familiarity. We’ve worked hands-on with Abodu, Plant Prefab, and Tuff Shed components, and we spec James Hardie siding when the design calls for it. We’re not guessing at how these products go together.
The name Lodgewick comes from a simple idea: a lodge is a small house on a larger property, which is exactly what an ADU is. That’s the work we do, and we’ve been doing it in San Jose since 2010 under the Kingswell family of companies. Garage Conversion ADU work is our focus, not a side hustle.
FAQs – Attached Garage Conversion
How much does an attached garage conversion cost in San Jose?
Attached garage conversions in San Jose typically cost $120,000 to $200,000, with smaller studio conversions at the low end and two-bedroom units with upgraded finishes at the high end. Your actual number depends on the garage’s condition, whether the foundation needs reinforcement, and the finish level you choose. Call (669) 266-4319 for a written estimate, no charge for the visit.
How long does an attached garage conversion take in San Jose?
Most attached garage conversions in San Jose take 4 to 7 months from the first site visit to final inspection, with permitting typically consuming 6 to 10 weeks of that timeline. The construction phase itself usually runs 3 to 5 months depending on the scope. We’ll give you a written timeline as part of your project plan.
Is it cheaper to convert an attached garage than to build a detached ADU?
Yes, converting an attached garage is usually $40,000 to $70,000 cheaper than building a detached ADU of the same size because the foundation, roof, and three of four walls already exist. You save on excavation, concrete, framing, and roofing that a detached build would require from scratch.
Do I need a permit to convert my attached garage in San Jose?
Yes, San Jose requires a building permit for any attached garage conversion, including plan review, Title 24 energy compliance, and a final inspection before the space can be legally occupied. We handle the full permit package as part of the project, and the permit fees are included in the written price you’ll see before work starts.
Can my attached garage conversion have its own kitchen and bathroom?
Yes, a legal ADU in San Jose can include a full kitchen and a full bathroom, and most attached garage conversions we build include both. The plumbing and electrical work require separate permits, which we pull as part of the project scope. If you’re planning to rent the space out, a full kitchen makes the unit far more rentable.
Will converting my attached garage affect my home’s resale value in San Jose?
Attached garage conversions in San Jose typically add significant resale value because the ADU counts as additional square footage and rental income potential, though some buyers specifically want garage parking. We’ve seen converted units appraise at $500 to $700 per square foot in current San Jose market conditions. If you have questions about how a conversion fits your long-term plans, we’ll talk through it before you commit to anything.
What does the 365-Day Done Right Promise cover?
The 365-Day Done Right Promise covers any workmanship or material issue that fails within one year of project completion, including a free return visit to fix it. The promise is in writing on every project before work begins, and you don’t have to argue or prove fault to get us back out. If the work isn’t right, we make it right.
Ready to Talk About Your Attached Garage?
If you’ve got an attached garage in San Jose and you’re wondering what it could become, call us at (669) 266-4319. We’ll set up a free site visit, measure the space, and get you a written price within about a week. No pressure, no price changes at the door, and a real person answers the phone whenever you call. Russ Delmar and the Lodgewick ADU San Jose team have been converting garages into homes since 2010, and we’d be glad to walk you through what’s possible on your lot.
Written by Russ Delmar, Owner at Lodgewick ADU San Jose, serving San Jose.
