Quick Answer: You can legalize an unpermitted ADU (sometimes called an “illegal unit,” “in-law unit,” or “granny flat”) in San Jose through the city’s Unpermitted Construction amnesty process. California SB 897 (2022) and San Jose’s local ADU ordinance require that applications to legalize existing ADUs be processed ministerially (no discretionary review) if the unit meets current ADU standards. The process: (1) Apply for a “legalization permit” at the San Jose Development Services Department; (2) City determines what upgrades are needed to bring the unit to current code; (3) A licensed contractor (CSLB required) makes the required upgrades; (4) Final inspection completes legalization. Cost depends heavily on the condition of the unit — typically $25,000-$100,000 in retrofits including electrical panel upgrade, smoke/CO detectors, GFCI outlets, egress window, and kitchen upgrades.
ADU Legalization Process in San Jose 2025
Helpful Resources:
- Pre-application review: Contact San Jose’s Development Services Department for a free pre-application meeting. Bring photos and floor plan sketches of the existing unit. The city will identify likely code deficiencies and provide a preliminary scope of required work
- Hire a licensed contractor or architect: CSLB-licensed contractor required. They prepare drawings showing the existing unit layout and proposed code-compliance upgrades. Some simpler units may not require an architect (prescriptive drawings suffice)
- Submit legalization permit application: Application goes to the San Jose Building Division. Per SB 897, the city has 60 days to approve or deny
- Code upgrade construction: Licensed contractor performs all required upgrades — typically electrical panel upgrade (most units need 100-200A service), smoke and CO detectors, GFCI protection, egress window in sleeping areas, bathroom ventilation, and kitchen hood/vent
- Final inspection and sign-off: Building inspector verifies all work. Permit closes. The unit is now legal — this clears it for legal rental, adds it to the assessor’s records as an ADU, and resolves any code enforcement issues
Quartz Construction handles the complete ADU legalization process in San Jose — from pre-application walkthrough to final inspection. We’ve helped many San Jose homeowners convert inherited illegal units into fully legal, rentable ADUs. CSLB #1003436 | Call (650) 749-7436.
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"Quartz Construction did an amazing job on our kitchen remodel. The team was professional, on time, and the results exceeded our expectations. Highly recommend to any Bay Area homeowner!"
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"Just finished our ADU garage conversion. The project came in on budget and on schedule — rare in the Bay Area! The rental income already started. Could not be happier with Quartz Construction."
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