Accessory Dwelling Units (ADUs) in California

California continues to expand its Accessory Dwelling Unit (ADU) program as a key strategy to address the state's ongoing housing shortage.

The California Department of Housing and Community Development (HCD) has updated its ADU Handbook for January 2025, reflecting recent legislative changes and providing updated guidance for homeowners and local jurisdictions interested in developing these secondary housing units.

ADUs, also known as granny flats, in-law units, or backyard cottages, allow property owners to add smaller residential units on their existing lots, effectively increasing housing density without requiring new land development.

Recent legislative activity has brought significant changes to state ADU law, with Senate Bill 477 taking effect in March 2024 and renumbering relevant sections of the Government Code that govern ADU and Junior ADU regulations.

The state is hosting a webinar on January 30, 2026, to educate stakeholders on the latest legal modifications.

Local ADU ordinances have grown exponentially as more cities and counties recognize these units as a viable solution for increasing affordable housing supply.

For California homeowners, ADUs represent an opportunity to generate rental income while contributing to housing availability, while property developers can leverage ADU regulations to maximize the residential potential of existing properties.

The state continues to offer various funding mechanisms, grants, and financial incentives to encourage ADU development across California communities.