San Jose ADU permits cost $2,800–$4,000+ depending on size and scope. See current fees, required steps, and how long approval takes in 2026.
An ADU permit in San Jose typically costs $2,800–$4,200 for a 600–800 sq ft unit, including plan check and inspection fees. The base permit fee is $715, plus 1.3% of project value. ADUs under 800 sq ft qualify for a 50% plan check fee reduction under state law.
Submit a full plan set — site plan, floor plan, elevations, and Title 24 energy calculations. First-time submissions often come back with corrections; plan for at least one round. After paying fees and getting your permit, inspections cover foundation, framing, rough MEP, insulation, drywall, and final.
ADU permits in San Jose take 45–90 days from first submission to permit issuance. Using San Jose's Pre-Approved ADU Plans Program can cut plan check to under 2 weeks. Construction inspections are scheduled separately as work progresses.
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