Clear ADU, SB 9, and Title 24 guidance for California homeowners
California ADU Co. helps homeowners and future homeowners understand accessory dwelling units, California ADU laws, local planning rules, Energy Code requirements, and the practical decisions that shape a project.
Built around official California guidance, plain-English explanations, and practical planning help.
Choose the path that fits your stage
I'm new to ADUs
Start with the basics, common ADU types, and what California law allows.
Learn more🏠I already own a property
Learn what to check first, which rules matter most, and where local review comes in.
Learn more🔍I'm comparing lots
See the main factors that can affect ADU feasibility, layout, and cost.
Learn more⚖️I need law or code help
Get simple guidance on California ADU laws, SB 9, and Title 24 for ADUs.
Learn more📍I want city-specific rules
Find local planning links, rule summaries, and what to verify before moving forward.
Learn moreEverything homeowners should understand before building an ADU
California ADU projects often involve more than one layer of rules. State law matters. Local ordinances matter. Energy code matters. Good planning matters too.
ADU basics
Learn what an ADU is, how it differs from a JADU, and which type may fit your property.
California ADU laws
Understand the statewide ADU framework and what cities can still regulate.
SB 9
See what SB 9 does, when it matters, and how it differs from a standard ADU project.
Title 24 / Energy Code
Understand when energy compliance applies, why the permit application date matters, and which topics usually affect ADU projects.
City rules
Review city pages that separate statewide law from local implementation.
Planning and costs
Get practical guidance on timelines, cost drivers, utility issues, and site constraints.
California-focused information, written for real homeowners
California ADU Co. is built to make complex ADU information easier to understand. The goal is not to overwhelm you with legal language. The goal is to help you understand what matters, what to verify locally, and what questions to ask before you spend time and money on the wrong next step.
Start with the most important guides
Download the California ADU Starter Guide
Get a simple overview of ADU basics, California rules, SB 9, Title 24, and the first questions to ask before planning your project.
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Common questions
What qualifies as an ADU in California?
An ADU (accessory dwelling unit) is a smaller secondary home on the same lot as a primary residence. It includes complete independent living facilities such as a kitchen, bathroom, and sleeping area. California law defines specific rules for ADU size, placement, and use.
What is the difference between an ADU and a JADU?
A JADU (junior accessory dwelling unit) is created within the existing walls of a primary home and is limited to no more than 500 square feet of interior livable space. A full ADU can be detached, attached, or converted from existing space and can be larger than a JADU.
What is SB 9?
SB 9 is a California law that allows certain housing developments of up to two primary units in a single-family zone, certain urban lot splits, or both, when statutory conditions are met. It is not the same as building an ADU, though the two topics are often discussed together.
Do ADUs need Title 24 compliance?
Yes. ADUs in California are subject to the Energy Code (part of Title 24). The permit application date determines which code cycle applies. The 2025 Energy Code applies to permit applications submitted on or after January 1, 2026.
Are city rules the same everywhere?
No. California has a statewide ADU legal framework, but cities and counties still administer permitting and can apply local objective standards where allowed by state law. That means application checklists, fees, timelines, and local requirements can vary significantly.