Drive through Evergreen, Berryessa or Cambrian and you will see them: new ADUs (accessory dwelling units) in backyards and converted garages. For many of my Vietnamese families, an ADU is how parents live close by while everyone keeps their privacy. For others it is rental income that helps cover a $9,000 mortgage. Here is the practical picture.
What San Jose allows (in general)
- Most single-family lots can add at least one detached ADU up to 800–1,200 sq ft and a smaller junior ADU inside the main house, under state law and the city's ADU program.
- Owner-occupancy is generally not required for ADUs permitted under current state rules.
- Setbacks are small (typically 4 ft side and rear), and no extra parking is required near transit.
- San Jose offers pre-approved ADU plans that speed up permits significantly.
Rules change, so confirm with the city's Planning Division before you design anything.
What it really costs
- Garage conversion: roughly $120,000–$200,000.
- New detached 1-bed ADU: roughly $250,000–$400,000 all-in (design, permits, utilities, construction).
- Timeline: 9–18 months from first drawing to occupancy.
Rents for a new 1-bedroom ADU in San Jose commonly fall in the $2,200–$3,000 range, which is why the math can work.
ADUs and resale value
Buyers pay a premium for a permitted ADU with its own entrance, kitchen and address — often most of the construction cost back, sometimes more. An unpermitted conversion is the opposite: lenders may not count it, insurers may balk, and I have to disclose it. If you are buying a home “with an in-law unit,” ask for the permit history first.
Three questions before you build
- Is this for family, rent, or resale? The design and budget differ.
- Can your sewer, electrical panel and water line handle a second unit? (Often the first hidden cost.)
- What will the finished property be worth versus what you will have invested?
I am happy to run the resale side of that math with you, and I can refer you to designers and builders who do ADUs in San Jose every week. Reach out here.
Tóm tắt tiếng Việt
ADU (nhà phụ sau vườn hoặc garage cải tạo) rất phổ biến ở San Jose: để cha mẹ ở gần, hoặc cho thuê phụ tiền nhà.
- Hầu hết lô nhà riêng được xây ADU tới 800–1,200 sq ft; thành phố có bản vẽ duyệt sẵn giúp xin permit nhanh.
- Chi phí: cải tạo garage khoảng $120,000–$200,000; xây mới khoảng $250,000–$400,000; mất 9–18 tháng.
- Cho thuê 1 phòng ngủ thường $2,200–$3,000/tháng.
- ADU có permit làm tăng giá nhà; không permit thì ngược lại — mua nhà có “in-law unit” phải hỏi giấy phép trước.
Ken có thể tính giúp phần giá trị bán lại và giới thiệu thợ xây ADU uy tín. Liên lạc Ken.
