ADU Cost in California 2025: Complete Price Breakdown and ROI
With rising home prices and a growing need for flexible living space, Accessory Dwelling Units (ADUs) have become a smart investment for California homeowners. But before breaking ground on a backyard cottage or garage conversion, it’s essential to understand the ADU cost in California in 2025 —and more importantly, whether the return on investment (ROI) is worth it. In this guide, we’ll break down the full cost of building an ADU in California and what kind of financial return you can realistically expect. What Is an ADU? An Accessory Dwelling Unit is a secondary housing unit on a single-family residential lot. These can take the form of a detached backyard cottage , garage conversion , basement apartment , or even an above-garage unit . ADUs are also known as: Granny flats In-law units Secondary units Casitas California law has made building ADUs easier than ever, especially with the 2025 ADU regulations aimed at increasing housing density and affordability....