ADU
ADU Basics for Homeowners Who Are Not Developers
10 min · Updated 2026-08-01
What an accessory dwelling unit is, why it is not a fancy shed, and the questions that decide whether the project is even legal on your lot.
An accessory dwelling unit is a second dwelling: sleeping, cooking, bathing. That is why it is not a shed with a nicer interior. Expect zoning, building, energy, fire, and utility review. California and several other states have rewritten local ADU rules — they have not deleted the building department.
The questions that kill projects early
Lot coverage, rear-yard depth, owner-occupancy, parking, separate meters, fire access, and whether the unit is a conversion, an addition, or a detached cottage. Run those before you interview a designer. See the ADU project page.
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Requirements vary by jurisdiction and by the specifics of a project. YardPermit publishes educational patterns and labeled estimates — not legal determinations, not construction documents, and not a bid. Verify with your local building department and a licensed contractor before you build.