Quick Answer: California’s ADU laws in 2025 allow: up to 1 ADU + 1 JADU per lot, maximum 1,200 sq ft for detached ADUs, 4-foot side/rear setbacks, no owner-occupancy requirement (as of 2020), and no minimum lot size requirement. San Jose also has its own ADU pre-approved plans program to fast-track permits.
California ADU Laws in 2025: Everything San Jose Homeowners Need to Know
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California’s ADU laws have changed dramatically since 2017. Multiple bills (AB 68, AB 587, AB 670, AB 671, SB 9, AB 2221, AB 976) have made it significantly easier and cheaper to build ADUs in San Jose and across California. Here’s a comprehensive guide to what’s legal in 2025.
What You’re Allowed to Build (2025)
- 1 Detached ADU — Up to 1,200 sq ft, or 50% of primary dwelling size, whichever is greater
- 1 Junior ADU (JADU) — Up to 500 sq ft within the existing home’s footprint
- Both an ADU + JADU — You can build both simultaneously on the same lot
- Garage conversion — Convert attached or detached garages to ADUs; replacement parking is not required
Key Setback Rules in San Jose (2025)
- Side and rear setbacks: 4 feet minimum for detached ADUs
- Front setback: Must comply with existing zone (typically 20 feet in San Jose residential zones)
- Height: 16 feet maximum for single-story detached ADUs (24 feet allowed in some cases for two-story)
- ADU within 1/2 mile of transit: Additional height flexibility may apply
No Owner-Occupancy Requirement (As of 2020)
As of January 1, 2020, California law prohibits cities from requiring owner-occupancy for properties with ADUs. You can build an ADU, rent out your primary home, and rent the ADU — or rent both units while you live elsewhere. This makes ADUs powerful investment vehicles.
HOA Restrictions on ADUs
California law (AB 670, effective Jan 1, 2020) prohibits HOAs from effectively banning ADUs. HOAs may impose reasonable design standards (matching exterior materials, paint colors) but cannot prevent ADU construction entirely. If your HOA tries to block your ADU, cite AB 670.
ADU Rental Income: Is It Taxable?
ADU rental income is taxable as ordinary income. However, you can deduct depreciation (27.5 years for residential rental), mortgage interest (proportional to ADU space), property taxes (proportional), repairs, insurance, and property management fees. Net effective tax rate on ADU income is often just 10–20% for most landlords in California.
Quartz Construction handles the complete ADU process in San Jose — design, permits, construction, and inspections. CSLB #1003436 | BBB A+ | 4.9⭐. Call (650) 749-7436 for a free ADU site assessment.
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