San Jose building & ADU permits

California mandates ministerial (by-right) approval of accessory dwelling units statewide, with a 60-day decision deadline and one ADU plus one junior ADU allowed on most single-family lots; owner-occupancy is generally not required.

SB 9 allows by-right duplexes and urban lot splits on single-family lots, and newer transit-oriented upzoning (SB 79) phases in from 2026.

San Jose permits accessory dwelling units under California's ministerial, by-right rules — detached, attached, and conversion ADUs, plus a junior ADU — so a conforming application is approved without a hearing and within the state's 60-day window. A single-family lot can generally add one ADU plus one junior ADU; there is no owner-occupancy requirement for a standard ADU, though a junior ADU still requires it, and parking is not required when the unit is near transit.

San Jose tiers its detached-ADU size limit by lot size, generally allowing up to 1,000 square feet on smaller lots and up to 1,200 square feet on larger ones. The city's signature offering is its Pre-Approved (Master Plan) ADU program: vendor designs are pre-stamped as code-compliant, and choosing one routes the project through the Permit Center's express service, where a building permit can potentially be issued same-day. Modifying a pre-approved plan removes it from that express track and returns it to standard review.

San Jose also publishes an ADU 'universal checklist' to help homeowners screen a project for the zoning clearances and special permits it may need before applying.

This is an informational summary — verify current rules with the city's planning/permitting department; not legal advice.

See also: California ADU law and what is an ADU?