ADU Builders in San Jose, CA
Looking for an ADU builder in San Jose? ADUs, garage conversions, and backyard cottages can add living space, rental income, or room for family. This page lists local ADU contractors and summarizes basic cost and permit considerations for San Jose homeowners.
San Jose is one of the highest-volume ADU markets in the country. With Bay Area rents and housing costs, backyard homes and garage conversions here often pencil out as long-term rental investments or housing for family.
Featured ADU contractors in San Jose
Serves San Jose and the greater Bay Area, part of a statewide California footprint
Prefab ADUs, Preapproved plans, Financing coordination
Serves San Jose and the greater Bay Area
Design-build, Preapproved plans, Custom ADUs, Permitting
Serves Santa Clara County (San Jose, Campbell, Cupertino, Los Gatos, Sunnyvale) and Alameda County (Oakland, Berkeley, Fremont, Hayward)
Attached ADUs, Detached ADUs, Conversion ADUs, Junior ADUs
Serves Santa Clara, San Mateo, and Alameda counties, including Oakland
Detached ADUs, Garage conversions, Permitting
Serves San Jose, with prefab ADU projects across Northern California
Prefab ADUs, Modular construction, Preapproved plans
Serves San Jose, Palo Alto, Menlo Park, Los Gatos, and surrounding Bay Area communities
Detached ADUs, Attached ADUs, Garage conversions, Permitting
Serves Bay Area including Oakland, Berkeley, San Jose, Palo Alto, and Fremont
Garage conversions, Design-build, Permitting
Serves San Jose and Northern California, with a showroom in San Jose
Prefab ADUs, Modular homes, Preapproved plans
Serves San Jose and the South Bay
Structural engineering, Preapproved plans, ADU design
Serves San Jose and Northern California counties including San Francisco, Alameda, Contra Costa, Santa Clara, San Mateo, and Marin
Design-build, Garage conversions, Junior ADUs, Permitting
Serves San Jose, Santa Clara, Sunnyvale, Palo Alto, Los Altos, Saratoga, Mountain View, and other South Bay/Peninsula cities
Design-build, Custom ADUs, Garage conversions, Permitting
Serves San Jose and the Bay Area
Preapproved plans, Detached ADUs, Construction management
Serves Silicon Valley and the Peninsula, including San Jose, Palo Alto, Mountain View, Los Gatos, and Sunnyvale
Design-build, Feasibility studies, Garage conversions, Junior ADUs
Serves San Jose and surrounding South Bay cities including Sunnyvale, Santa Clara, Los Gatos, and Mountain View
Detached ADUs, Garage conversions, Permitting
ADU costs in San Jose
General estimated ranges:
- Garage conversion: $110,000–$200,000
- Detached ADU: $200,000–$450,000
- Design/permitting: varies by project
Estimates only — actual costs vary by site, size, and finishes. See the full San Jose ADU cost guide.
Common ADU project types
- Detached ADU
- Garage conversion — see San Jose garage conversion contractors
- Junior ADU
- Basement conversion
- Prefab ADU
ADU permits in San Jose
San Jose has an established ADU program with pre-approved (master-plan) ADU vendors and a dedicated ADU permitting pathway. Most single-family lots qualify for a detached ADU plus a JADU; the city has actively streamlined size and setback standards.
State law caps review of complete applications at 60 days. San Jose's pre-approved ADU program can cut plan review significantly; custom builds commonly take 3–5 months from design to permit.
Questions to ask an ADU builder
- Have you completed ADUs in this city?
- Can you help with design and permits?
- Do you handle utility connections?
- Can you show recent examples?
- Are you licensed and insured?
FAQ
How much does an ADU cost in San Jose?
Most detached ADUs in San Jose land in the $200,000–$450,000 range all-in, depending on size, finishes, and site conditions. Garage conversions typically run $110,000–$200,000. These are editorial estimates — get multiple quotes for your specific property.
Do I need a permit to build an ADU in San Jose?
Yes. Every ADU and garage conversion in San Jose requires building permits. The good news: California law requires ministerial (no public hearing) approval for code-compliant ADUs. State law caps review of complete applications at 60 days. San Jose's pre-approved ADU program can cut plan review significantly; custom builds commonly take 3–5 months from design to permit.
How long does it take to build an ADU in San Jose?
Plan for 3–6 months of design and permitting, then 4–8 months of construction for a detached ADU. Garage conversions are usually faster — often 3–5 months of construction once permits are issued.
Can I rent out my ADU in San Jose?
Yes — long-term rentals (30+ days) of ADUs are allowed statewide in California. Short-term rental rules vary by city, so check San Jose's short-term rental ordinance before planning Airbnb-style use.
Does an ADU add value to my home in San Jose?
Generally yes. Appraisals vary, but a permitted ADU adds livable square footage and rental income potential, which supports resale value. Note that ADUs also increase your property tax assessment on the new construction value.
What's the difference between an ADU and a JADU?
A Junior ADU (JADU) is a unit of up to 500 sq ft created within the existing home, with an efficiency kitchen and shared or separate bath. A standard ADU is a full independent dwelling — attached, detached, or converted from a garage. Many San Jose lots qualify for one of each.
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