Zoning Glossary

Junior ADU (JADU)

A Junior ADU (JADU) is a California-specific category of secondary dwelling unit created within the existing walls of a single-family residence or an existing accessory structure, limited in size to a compact unit that fits within the existing footprint. JADUs were established in California law to enable low-cost conversion of existing interior spaces — oversized bedrooms, finished garages, basement areas — into secondary housing without requiring new construction. A JADU must have a separate exterior entrance and is permitted to share utility connections with the primary dwelling, which distinguishes it from a full ADU and substantially reduces conversion costs.

ADU

In Practice

Because a JADU is created by converting existing space rather than building something new, it typically costs substantially less to create than a detached or new-construction ADU. JADUs are permitted to have an efficiency kitchen rather than a full kitchen, and they may share a bathroom with the primary dwelling. The JADU framework — including its associated fee waivers and ministerial approval pathway — is a California-only legal concept. Other states may permit functionally similar interior conversions under local ADU rules, but the specific JADU protections and fee structures apply only in California.

Source: ADU vs JADU: What's the Difference and Which Can You Build? · Verified June 1, 2026

Related Terms

Accessory Dwelling UnitDetached ADUAttached ADUGarage Conversion ADUMinisterial Approval

Related Guides

ADU vs JADU: What's the Difference and Which Can You Build?ADU Rules in California: Complete 2026 Guide

Source: PropertyZoned Zoning Guide — ADU vs JADU: What's the Difference and Which Can You Build?. Last verified June 1, 2026.

Last updated: June 1, 2026
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Junior ADU (JADU) — Zoning Term Definition | PropertyZoned