How to Get an ADU Permit in San Jose: Step-by-Step

By Raven Vuong

Getting an ADU permit in San Jose does not have to be overwhelming. The City of San Jose has streamlined its ADU permitting process in response to California housing laws, but there are still specific steps, forms, and fees you need to understand before you break ground. This guide walks you through the entire process so you know exactly what to expect when building an ADU in the Bay Area.

Whether you are building a detached unit in your backyard, converting a garage, or adding an attached ADU, the permit process follows the same general path.

Before You Start: ADU Eligibility in San Jose

Zoning and Lot Requirements

San Jose allows ADUs on any residentially zoned lot with an existing or proposed single-family or multifamily home. Under current California law, local jurisdictions cannot impose minimum lot sizes for ADUs. Your lot must have legal access and be served by water and sewer. If your property is in a flood zone or has other environmental constraints, additional requirements may apply.

ADU Types Allowed in San Jose

San Jose permits detached ADUs (up to 1,200 square feet), attached ADUs, garage conversions, and Junior ADUs (JADUs up to 500 square feet within the existing home). You can have both an ADU and a JADU on the same single-family lot, giving you the potential for three housing units on one property. Details are available on the City of San Jose ADU page.

Step-by-Step ADU Permit Process

Step 1: Design and Plans

Hire a designer or architect to prepare construction drawings that comply with California building code and San Jose local requirements. Plans must include site plan, floor plan, elevations, structural details, plumbing, electrical, and mechanical layouts. This phase typically takes two to four weeks and is the foundation of a smooth permit process.

Step 2: Submit Your Application

Submit your plans and permit application through the City of San Jose Development Services Permit Center. San Jose accepts online submissions through its ePermit portal. Include all required documents: the application form, construction plans, Title 24 energy calculations, and the applicable fees.

Step 3: Plan Review

The city reviews your plans for compliance with zoning, building, fire, and utility requirements. Under California law, San Jose must complete ADU plan review within 60 days of receiving a complete application. In practice, review times range from four to eight weeks depending on workload and the complexity of your project.

Step 4: Address Corrections

It is common to receive a correction letter after plan review. The city may request changes to setback calculations, structural details, or energy compliance documentation. Respond to corrections promptly with revised plans. This back-and-forth typically takes two to four weeks.

Step 5: Permit Issuance

Once all corrections are resolved, the city issues your building permit. Pay the remaining permit fees and you are cleared to begin construction. The permit is valid for a set period (typically 12 to 18 months), during which all work must be completed or an extension requested.

Inspections During Construction

During construction, you will need to schedule inspections at key milestones: foundation, framing, rough plumbing, rough electrical, insulation, and final. Each inspection must pass before the next phase of work can proceed. Your contractor should coordinate the inspection schedule with the city to avoid delays. The final inspection confirms the ADU is safe for occupancy and triggers the certificate of occupancy.

Common Delays and How to Avoid Them

The most common cause of permit delays is an incomplete application. Missing energy calculations, incorrect setback measurements, or plans that do not meet current building code will result in a correction letter and add weeks to your timeline. Work with a designer who has experience with San Jose ADU permits specifically. Other delays include slow contractor scheduling, material supply issues, and failing inspections. A contingency of two to four weeks in your timeline helps account for these variables.

When to Hire Professional Help

While some homeowners manage the permit process themselves, hiring an experienced ADU builder who handles design, permits, and construction as a package saves significant time and reduces the risk of costly mistakes. An experienced builder knows exactly what San Jose plan checkers look for and can prepare plans that pass review on the first or second submission. 9Builders manages the entire ADU process from design through final inspection for homeowners throughout San Jose and the Bay Area.