Best ADU Builders in the SF Bay Area (2026)

ADU construction costs in the SF Bay Area run 40-60% higher than the statewide average. A 750 sq ft detached unit that costs $220,000 in Sacramento routinely bids at $340,000 to $400,000 in San Jose, Oakland, or Palo Alto. At those price points, hiring the wrong contractor is not a $20,000 mistake — it is a six-figure one. The best ADU builders in the SF Bay Area are the ones you can verify before signing: active CSLB license, bond on file, workers’ comp current, and a complaint history that holds up when you check it yourself. Every builder on this list passed that verification before appearing on the page.

CSLB logged over 400 ADU-related complaints statewide in the past two years. Anchored Tiny Homes took $12.8 million from 450+ homeowners before filing bankruptcy. Multitaskr arranged $15 million in construction loans under homeowners’ names and built nothing. These weren’t fly-by-night operations. They had websites. They had Instagram accounts. They looked legitimate.

A CSLB license check takes 30 seconds at cslb.ca.gov. Most homeowners skip it. That’s the gap. Every builder on this page and in our SF Bay Area directory has been checked against CSLB records — not once at listing time, but on an ongoing basis through our LiveVerify system. For the full list of documented fraud cases, see our ADU Contractor Scams in California guide.

We started with 6,869 active Class B general building contractors in the 10-county Bay Area from the CSLB master database. Then we filtered.

• Active CSLB license — Class B (General Building) with no suspensions or revocations.
• Contractor bond on file — $25,000 surety bond confirmed active.
• Workers’ compensation — Either insured through a carrier or legally exempt as a sole proprietor.
• No unresolved CSLB complaints — Clean complaint history at time of verification.
• ADU-specific work — Evidence of actual ADU construction: portfolio photos, ADU-focused website, project reviews, or city pre-approval status. A Class B license alone doesn’t make someone an ADU builder.

That last filter is what separates this list from a database dump. Thousands of Bay Area contractors hold a Class B license. The builders below actually build ADUs.

Acton Construction Inc

Campbell · CSLB #638333 · Licensed since 1992 · 34 years

Acton is the longest-running ADU-focused builder on this list. Over three decades of residential construction in the South Bay, with a dedicated ADU division (Acton ADU) that handles design, permitting, and construction as a single package. They’ve built backyard homes across San Jose, Palo Alto, and the wider Silicon Valley. Class B licensed with full workers’ comp coverage.

Sigura Construction Inc

Sunnyvale · CSLB #865155 · Licensed since 2005 · 21 years

Diamond Certified for 19 consecutive years. A+ BBB rating for 18+. Sigura handles ADU construction, garage conversions, and custom builds across San Mateo and Santa Clara counties. That Diamond Certified streak means they’ve maintained top ratings through independent homeowner surveys every single year since 2007. Not many contractors in any category can say that.

Berkeley Design Build Inc

Oakland · CSLB #790793 · Licensed since 2001 · 25 years

A quarter century of residential design-build in the East Bay. Berkeley Design Build works in collaboration with Linvill & Pond Architects on ADUs, additions, and whole-house remodels. The design-build model means one contract covers architecture and construction — fewer handoffs, fewer miscommunications, one team accountable for the result.

Brother And Brother Builders

San Jose · CSLB #887389 · Licensed since 2006 · 20 years

Top-rated on Yelp in the San Jose market. Twenty years of residential construction with a focus on ADUs, home additions, and full renovations. Family-owned operation with repeat-client referrals driving most of their work — which is how you want to find a contractor, not through Instagram ads.

McDunn Construction Inc

Berkeley · CSLB #966969 · Licensed since 2011 · 15 years

ADU-only. McDunn doesn’t do kitchens, bathrooms, or commercial work. They build accessory dwelling units in Berkeley, Oakland, Albany, El Cerrito, and Alameda. Over 20 completed ADU projects since 2017. Winner of the 2019 Bay Area Remodeling Award and a NARI Contractor of the Year finalist. When a builder does one thing and wins awards for it, that tells you something.

Bay Area Design & Construction

Los Gatos · CSLB #924105 · Licensed since 2008 · 18 years

Full-service design-build firm with 20 years of experience across the South Bay and Peninsula. ADUs, custom homes, and luxury renovations. Their portfolio shows completed projects from Los Gatos to Palo Alto — markets where permitting is complex and construction costs run 15-25% above the regional average.

Manzanita Design Build

Oakland · CSLB #1034108 · Licensed since 2017 · 9 years

Design and construction firm led by founder Ben Obriecht, focused on the East Bay. Manzanita publishes a full ADU project gallery on their site — before, during, and after photos of completed backyard units in Oakland and Berkeley. That kind of transparency is rare. You can see exactly what they build before you call.

Current market conditions

The Bay Area is the most expensive ADU construction market in California. Labor costs run 20-40% higher than Sacramento or San Diego. Material delivery to tight urban lots adds cost. Permitting timelines vary wildly by city — San Jose can approve a pre-approved plan in weeks, San Francisco can take months.

Demand is strong. Bay Area homeowners build ADUs for three reasons: housing aging parents (most common in the suburbs), generating rental income (most common in urban areas), and adding property value (everywhere). At Bay Area rents, a well-built ADU can generate $2,000-$4,000/month — enough to cover the construction loan payment in many cases.

Typical costs

ADU Type	Cost Range
Garage Conversion	$100,000 – $200,000
JADU	$80,000 – $150,000
Attached ADU	$200,000 – $400,000
Detached ADU	$250,000 – $500,000
Prefab / Modular	$150,000 – $350,000

These ranges include permitting, site prep, construction, and basic finishes. Premium finishes, difficult site access, or complex engineering add 10-30%. San Francisco and Peninsula cities tend to run highest. East Bay and South Bay are typically 15-25% lower. For a comparison to other California markets, see our Sacramento cost guide.

CalHFA ADU Grant Program

California’s CalHFA ADU Grant provides up to $40,000 for qualifying ADU projects. The grant applies statewide, including all Bay Area counties. Eligibility depends on income limits and property requirements — not all projects qualify, but the ones that do get a meaningful offset on a $300,000+ build. Details and application: our CalHFA grant guide.

The verification we do is a starting point. Before you sign a contract, do your own checks:

1. Verify the license yourself. Go to cslb.ca.gov and enter the license number. Confirm it’s active, the bond is current, and there are no open complaints. Takes 30 seconds. For a walkthrough, see our license verification guide.
2. Never pay more than $1,000 or 10% upfront. California law (B&P Code 7159.5). Any contractor asking for more is breaking the law.
3. Tie payments to inspected milestones. Foundation passes inspection, you pay for foundation. Framing passes, you pay for framing. Never pay ahead of verified progress.
4. Ask how many active projects they’re running. A builder with 5-10 is manageable. A builder with 50+ is overextended. That’s how collapses happen.
5. Check your city’s permit requirements. San Jose, San Francisco, and Oakland all have different ADU rules. Your builder should know your jurisdiction’s specific requirements without hesitating.
6. Get 3-5 bids. Don’t hire the first contractor you talk to. Compare scope, timeline, and price across multiple builders. The cheapest bid isn’t always the best — but neither is the most expensive.

How much does it cost to build an ADU in the SF Bay Area?

$100,000 for a basic garage conversion up to $500,000+ for a large detached unit with premium finishes. The median cost for a 600-800 sq ft detached ADU in the Bay Area runs $300,000-$350,000. San Francisco and Peninsula cities cost 15-25% more than East Bay or South Bay.

How long does it take to build an ADU in the Bay Area?

10 to 18 months from permit submission to move-in. Permitting takes 6 weeks to 6 months depending on your city — San Jose is fastest with pre-approved plans, San Francisco is slowest with design review. Construction runs 4 to 8 months for most projects.

What license does a contractor need to build an ADU in California?

Class B — General Building Contractor. This is the standard license for new residential construction including ADUs. Some contractors also hold C-class specialty licenses (C-36 plumbing, C-10 electrical), but the Class B is what authorizes them to build the structure. Verify at cslb.ca.gov.

Which Bay Area cities have pre-approved ADU plans?

San Jose has the most established pre-approved ADU program, with standardized plans available through the Development Services Permit Center. Several other Bay Area cities are adopting similar programs. Pre-approved plans cut weeks off the permitting timeline because the city has already reviewed and approved the design. Ask your builder if they work with pre-approved plans in your jurisdiction.

Can I rent out my ADU in the Bay Area?

Yes for long-term rentals. Short-term rental rules (Airbnb, VRBO) vary by city — San Francisco, Oakland, and San Jose each have their own ordinances. Most Bay Area ADU owners rent long-term at $2,000-$4,000/month depending on size, location, and finishes. Check your city’s specific short-term rental rules before assuming you can list on Airbnb.

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

No owner-occupancy requirement for standard ADUs under current California law. JADUs (junior ADUs under 500 sq ft within the existing home) may require the property owner to live on-site. This applies statewide including all Bay Area cities.

How do I verify an ADU builder’s license in California?

Go to cslb.ca.gov. Enter the contractor’s license number or business name. The detail page shows license status, classification, bond information, workers’ comp status, and any complaints or disciplinary actions. This is free, public, and takes 30 seconds. Every builder in our SF Bay Area directory has been verified through this process.

What’s the difference between a prefab and a site-built ADU?

A prefab (modular) ADU is manufactured in a factory and delivered to your property for installation. A site-built ADU is constructed entirely on your lot from the ground up. Prefab is typically faster (3-5 months vs 5-8 months) and can cost less, but site-built offers more customization. Both require permits. Both must meet the same building codes. The right choice depends on your lot, your budget, and how custom you want the design.