Best ADU Builders in San Jose, CA
The average cost to build an ADU in San Jose is $250–$400 per square foot. Top-rated builders include Acton ADU, Villa Homes, Nestadu.
Every builder below is CSLB license-verified, bonded, and insured — vetted before they ever reach a homeowner. Browse ratings and real reviews, compare starting prices, or let us match you with the best fit for your lot and budget. It's free; we're paid by the builders, not you.
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What kind of ADU are you planning?
3 builders in San Jose, CA
Last updated June 26, 2026
License VerifiedActon ADU
Serving San Jose, CA · Campbell, CA
“Acton works across California and it shows — their process is dialed in. Standardized floor plan kept costs predictable and the build quality was excellent.”— Rachel P., Homeowner
Pricing on request
A California general building contractor licensed since 1992, serving the LA market statewide.
License VerifiedVilla Homes
Serving San Jose, CA · San Francisco, CA
“Excellent job! The Villa crew from start to finish nothing short of professional. Foundation, home delivery, finish work etc top notch. I would recommend Vill…”— M Ferreira
Pricing on request
Tech-enabled prefab ADU builder delivering turnkey backyard homes across California.
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License VerifiedNestadu
Serving San Jose, CA · Mill Valley, CA
“Nestadu did a great job on my backyard ADU. Their team was professional, and the final result looks fantastic—well-built and blends in nicely with my home. Pric…”— Stephen Reid
Pricing on request
Custom and prefab ADUs for California homeowners — design, permit, and build, turnkey.
Frequently Asked Questions
- How much does it cost to build an ADU in San Jose, CA?
- In San Jose, ADUs typically run $250–$400 per square foot all-in. A detached 800 sq ft unit commonly lands between $230k and $340k depending on finishes, site conditions, and utility connections. Garage conversions are the most affordable path, often under $180k.
- How long does it take to build an ADU in San Jose?
- Plan to budget 6–12 months end to end. California law caps ADU plan check at 60 days for compliant designs, and construction usually takes 4–8 months after permits are issued.
- Do I need a permit to build an ADU in San Jose?
- Yes. All ADUs require a building permit, but California mandates ministerial (non-discretionary) approval for compliant units, so there's no public hearing or design review. Your builder typically pulls the permit on your behalf.
- How do I choose a builder in San Jose?
- Confirm the contractor holds an active CSLB license, is bonded and insured, and has built ADUs in San Jose specifically. Every builder in this directory is license-verified. Use "Get a Quote" to be matched with the best fit for your lot and budget.
ADU costs in San Jose: city vs. metro vs. state
Building an ADU in San Jose runs roughly $250–$400 per square foot all-in. Here's how the city benchmarks against the broader metro and statewide averages.
| Area | Avg. cost / sq ft | Typical 800 sq ft ADU |
|---|---|---|
| San Jose | $250–$400 | $200,000–$320,000 |
| San Jose metro | ~$320 | ~$256,000 |
| California (CA) | ~$330 | ~$264,000 |
Cost by ADU type in San Jose
| ADU type | Typical size | Project cost | Timeline |
|---|---|---|---|
| Detached ADU | 600–1,200 sq ft | $180,000–$420,000 | 8–12 months |
| Attached ADU | 400–800 sq ft | $140,000–$300,000 | 6–10 months |
| Garage Conversion | 400–600 sq ft | $90,000–$180,000 | 4–7 months |
| JADU (Junior ADU) | ≤ 500 sq ft | $60,000–$140,000 | 3–6 months |
ADU rules & permits in San Jose, CA
Local ADU permitting in San Jose follows California state ADU law, which caps plan-check at 60 days for compliant units. Confirm setbacks, height, and parking rules with the local building department.
| Jurisdiction | Permit timeline | Permit fees | Notes |
|---|---|---|---|
| City of Los Angeles | 60-day plan check (by law) | $3k–$8k | Pre-approved Standard Plan program available |
| Unincorporated LA County | 60–90 days | $4k–$10k | Ministerial approval for compliant ADUs |
| Statewide (CA) | 60 days max by statute | Varies | Owner-occupancy requirement waived through 2030 |
Financing your ADU in San Jose
Common ADU funding paths include renovation and construction loans, a HELOC, or a cash-out refinance. ADU-specific lenders underwrite against after-build value, which often unlocks more than a standard HELOC.
Construction / renovation loan
Funds released in draws as the build hits milestones; underwritten against after-build value.
HELOC / home equity
Borrow against existing equity. Fast to set up if you have 20%+ equity.
Cash-out refinance
Replace your mortgage and pull equity as cash — best when rates are favorable.
ADU-specific lenders
RenoFi and similar lenders underwrite the projected value the ADU adds, often unlocking more.
Pre-ADU Checkup — $499 — Get finalized permits, a pre-ADU checklist, and an on-site feasibility visit. Homeowners save $1,000s by doing this before engaging a contractor.