So you want to build an ADU in California? Here’s what you need to know

California homeowners and property developers looking to add housing units to their properties have increased opportunities through Accessory Dwelling Units (ADUs) and Junior Accessory Dwelling Units (JADUs), according to updated state guidance released in January 2025.

These secondary housing structures, commonly known as granny flats, in-law units, or backyard cottages, represent a growing solution to California's housing shortage as cities and counties increasingly adopt ADU-friendly ordinances.

The California Housing and Community Development Department (HCD) has emerged as the state's primary resource for local ADU regulations, supporting municipalities in developing frameworks that encourage these housing additions.

Recent legislative changes have streamlined the regulatory landscape, with Senate Bill 477 renumbering relevant sections of the Government Code to clarify state ADU and JADU requirements as of March 2024.

Property owners considering ADU development can access various funding options, including potential grants and financial incentives designed to offset construction costs.

The state has scheduled a comprehensive webinar for January 30, 2026, to address the latest modifications to ADU law, reflecting the ongoing evolution of these housing policies.

For developers and homeowners, ADUs present an opportunity to increase property value while contributing to California's housing supply, with simplified approval processes making these projects more accessible than traditional development options.