Do I Need a Permit to Build an ADU in San Jose?
Yes — all ADU construction in San Jose requires permits from the Department of Planning, Building and Code Enforcement. This includes detached ADUs, attached ADUs, garage conversions, and Junior ADUs. Unpermitted ADUs create legal liability and cannot be legally rented.
Permits Required for ADU Construction
- Building Permit: Required for all structural work, framing, and foundation.
- Electrical Permit: Required for new or modified electrical systems.
- Plumbing Permit: Required for kitchen and bathroom plumbing.
- Mechanical Permit: Required for HVAC systems.
ADU Permit Process in San Jose
- Pre-application consultation with city planning staff (optional but recommended)
- Submit complete permit application with architectural and structural drawings
- Plan check review (4–16 weeks depending on complexity)
- Permit issuance and payment of fees
- Construction with required inspections at each phase
- Final inspection and Certificate of Occupancy issuance
Apply through the City of San Jose Online Permits Portal.
We Handle All Permits
San Jose ADU & Remodeling manages the entire permit process as part of our ADU Construction Service. You don't have to navigate city hall — we do it for you.
Unpermitted ADUs are illegal to rent and can result in fines, mandatory demolition, and difficulty selling your property. California does have an amnesty process for some unpermitted units, but it's complex and not guaranteed. Always get proper permits.
Permit fees are calculated based on construction valuation. For a typical detached ADU, expect $5,000–$20,000 in permit and plan check fees. Units under 750 sq ft are exempt from most impact fees under state law.