Converting the garage you barely use into a fully equipped accessory dwelling unit (ADU) is one of the quickest ways to create extra living space—and extra income—in the Bay Area’s high-priced housing market.
Done right, a 350- to 450-square-foot suite can rent for more than many studio apartments, all while adding to your property’s resale value.
Below, we break down the key rules, costs, and seven standout contractors who specialize in transforming garages into ADUs.
Why Garage Conversions Are the Fastest Path to Added Living Space
Many Bay Area homeowners already have the basic structure for an ADU sitting at the end of the driveway. Because the slab, walls, and roof are in place, garage conversions typically cost about 18 percent less than building a detached backyard cottage.
They also sidestep stringent setback rules and can be finished in as little as six months.
What to Know Before You Hire
- Faster permits – A 2025 update to California’s SB 9 forces local agencies to approve or deny ADU applications within 60 days, down from 120 days previously.
- Typical costs – A 400-square-foot conversion runs about $215,000 in the Bay Area—still steep, but markedly cheaper than moving.
- Rising demand – ADUs accounted for 12 percent of all new residential units approved in California during Q2 2025—proof that officials are warming up to the concept.
- Local hot spot – Permit applications in San Jose alone jumped from roughly 350 in 2020 to 1,100 in 2024.
Budget for seismic upgrades, utility tie-ins, and Title 24 energy-code compliance. Then interview at least two design-build teams—starting with the experts below.
The Ranking Criteria
We evaluated dozens of firms on license standing, ADU-specific portfolios, customer reviews, pricing transparency, and ability to manage permits across Bay Area jurisdictions.
Every contractor below can deliver a turnkey garage conversion; the sequence reflects overall value for money rather than size alone.
The 7 Best Garage-Conversion ADU & Addition Contractors
1. Valley Boutique Builders
Design-build firm headquartered in Los Altos, Valley Boutique Builders focuses on turning underused garages into code-compliant ADUs across Santa Clara and San Mateo counties.
VBB offers a full design-build approach and coordinates needed layout changes and structural upgrades, including seismic work, through its project team.
- VBB covers the Bay Area, San Jose, Sunnyvale, Palo Alto, Los Altos, Atherton, and Woodside.
- One-stop service: Design-build approach that covers consultation, design development, permit coordination, and construction through final finishes.
- VBB holds an active CSLB license with no current disciplinary actions.
- A gallery showcasing dozens of layouts.
Valley Boutique Builders is the go-to choice if you want a truly turnkey path and minimal municipal headaches. Book a free on-site consultation through the Valley Boutique Builders website.
2. Acton ADU
Campbell-based Acton ADU has completed more than 300 Bay Area accessory units since 2019 and is now doubling down on garage conversions. Its proprietary “Acton ADU 360 Roadmap” shepherds homeowners from feasibility to leasing strategy.
The company averages permit approval in 56 days across most Santa Clara County cities, with transparent pricing that starts at $199,000 for a 350-square-foot conversion.
- Design library featuring 20+ pre-engineered floor plans optimized for garages.
- Handles PG&E service-panel upgrades in-house to eliminate subcontract delays.
- Provides complimentary rental-income projections using live Zillow comps.
- Lifetime structural warranty on foundation and framing.
Acton ADU suits homeowners who want a proven, process-driven approach and rental-ready finishes without custom-design price tags.
3. HDR Remodeling
This Berkeley design-build firm has a 30-year legacy in whole-house remodels and launched a dedicated ADU division in 2021. HDR Remodeling is known for energy-efficient retrofits that boost Title 24 compliance—important when converting attached garages.
Service coverage spans Alameda and Contra Costa counties, with typical garage-conversion budgets of $220,000 to $270,000, often including solar-ready electrical upgrades.
- Certified GreenPoint-rated builder for eco-friendly materials.
- The three-phase client portal tracks selections, schedule, and invoices.
- Seismic-retrofit expertise for pre-1950 detached garages.
- Partnerships with architects for historic-district approvals.
If sustainability and meticulous craftsmanship top your list, HDR Remodeling delivers a greener ADU without the usual Bay Area headaches.
4. New Avenue Homes
Emeryville-based New Avenue is a tech platform that matches homeowners with vetted architects and builders. More than 500 ADUs have been completed statewide through the marketplace, and its “Garage Conversion Starter” pairs a fixed-fee design package (from $18,000) with competitive builder bids.
A cloud dashboard keeps budgets and permits transparency, and the average construction timeline clocks in at 5–7 months for a 400- to 500-square-foot conversion.
- Marketplace approach yields three competing bids for every build.
- Rental-income calculators and lender introductions are built into the platform.
- Experience navigating tricky Oakland setback waivers.
- Optional prefab panelized wall systems can shave weeks off framing.
Pick New Avenue if you value price transparency and want to comparison-shop builders without the legwork.
5. Element Home Remodeling
Based in Palo Alto, Element Home Remodeling blends modern design aesthetics with smart-home integrations in every ADU.
The firm earned a 2023 Houzz “Best of Service” award and maintains a 4.9-star average across 120+ client reviews.
Garage conversions generally cost between $200,000 and $260,000, depending on automation features, and appeal to tech professionals seeking a rentable yet guest-friendly suite.
- Standard package includes Lutron lighting, Nest climate control, and an EV-charger circuit.
- VR walkthroughs let you preview the space before a single stud is cut.
- Navigates Palo Alto’s stringent green-building checklists without outside consultants.
- Post-completion support features a one-year maintenance check.
For a high-tech ADU that meshes with contemporary upgrades in the main house, Element brings Silicon Valley polish.
6. Carmichael Builders
Family-owned and based in Walnut Creek, Carmichael Builders has focused on structural additions for more than 40 years and recently pivoted to ADUs.
The company is noted for cost-effective seismic retrofits along the Hayward Fault corridor.
Garage conversions typically start at $185,000, making Carmichael one of the more budget-friendly East Bay options. GuildQuality surveys show a customer-satisfaction score of 96 percent.
- In-house structural engineering reduces change-order surprises.
- Phased payment schedules tied to inspection milestones.
- Uses recycled denim insulation for superior soundproofing.
- Free permit-pulling service for senior homeowners.
Carmichael Builders is ideal for cost-conscious East Bay homeowners who still want solid engineering and a personal touch.
7. Mighty Buildings
Oakland startup Mighty Buildings prints composite wall panels in a factory, delivering ADUs in half the onsite time of stick-built methods. It’s new “Garage-Attach” line converts existing slab-on-grade garages with prefab modules.
Base price starts at $225,000, but installation to move-in averages just 90 days. The panels outperform Title 24 energy standards by 30 percent.
- 3-D printing cuts material waste by up to 60 percent.
- Integrated solar-roof option generates roughly 4 kW.
- Zero-VOC interior finishes cater to health-conscious clients.
- Financing through LightStream offers unsecured loans up to $250,000.
Homeowners who prize speed, sustainability, and cutting-edge tech will appreciate Mighty Buildings’ factory-precision approach.
ADU Permit Trends: San Jose Leads the Charge
Applications for accessory dwelling units in San Jose increased from roughly 350 in 2020 to more than 1,100 in 2024—a 214 percent rise that reflects both city incentives and statewide reforms.
Expect surrounding cities to follow suit as pressure mounts for gentle-density housing.
Cost & ROI Calculator: How Much Could Your Garage Earn?
At a median Bay Area rent of $2,200 for a 400-square-foot studio, a $215,000 garage conversion can cash-flow $1,450 per month after setting aside 25 percent for vacancy, maintenance, and utilities.
That’s a payback period of roughly 12 years, not including the equity boost to your property. Factor in tax deductions for depreciation, and you could hit breakeven even sooner.
Conclusion
A garage-conversion ADU can unlock steady rental income, multigenerational living, or a private home office—often in less time and for less money than building a detached unit.
By partnering with a seasoned design-build team—whether the tech-savvy crews at Element or the turnkey experts at Valley Boutique Builders—you’ll navigate permits faster, control costs, and move tenants (or family) in sooner.
Ready to reclaim your garage and reap the returns? Start planning today.
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