What Is ADU Building? A Complete Guide for San Jose Homeowners
An Accessory Dwelling Unit (ADU) — also known as a granny flat, in-law suite, backyard cottage, or secondary suite — is a self-contained residential unit on the same property as a primary single-family or multi-family home. ADU building refers to the design, permitting, and construction of these secondary units.
Types of ADUs
- Detached ADU: A fully separate structure in the backyard, not connected to the main house.
- Attached ADU: Connected to the main home but with a separate entrance and living facilities.
- Garage Conversion ADU: An existing garage converted into a habitable living space.
- Junior ADU (JADU): Up to 500 sq ft, created within the existing home's footprint.
- Above-Garage ADU: A unit built on top of an existing or new garage structure.
What Makes a Unit an ADU?
To qualify as an ADU under California law, the unit must have: its own entrance, a full kitchen (sink, cooking appliance, refrigerator), a bathroom, and sleeping space. It must also comply with applicable building codes enforced by the City of San Jose.
See Accessory Dwelling Unit on Wikipedia for a detailed definition.
ADU Building in California: State Law Summary
California has been the national leader in ADU reform. Key laws include:
- AB 68 (2020): Eliminated single-family zoning restrictions on ADUs statewide.
- SB 9 (2022): Allows lot splits on single-family parcels, enabling more ADU opportunities.
- AB 2221 (2023): Clarified size limits and exempted small ADUs from impact fees.
The California HCD ADU page maintains current guidance.
Yes. ADUs can be rented to long-term tenants. Short-term rentals (e.g., Airbnb) may be subject to additional local regulations. Check with the City of San Jose Planning Department for current short-term rental rules.
California eliminated owner-occupancy requirements for ADUs through January 1, 2025. However, rules can change — consult with our team or the city's planning department for the most current requirements.
Generally yes, as California eliminated owner-occupancy requirements. Multi-family properties can also add ADUs in some configurations. Contact us for a site-specific assessment.