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Build an ADU or convert a garage

Always requires permits, and this is the project where zoning approval — not the building permit — is usually the real obstacle.

Permit rules are set locally, so the ZIP decides which state code applies and which office you would be dealing with. We use it to look up the jurisdiction and nothing else.

Why nobody can just tell you

Permitting in the United States is run by thousands of separate authorities, and each one can amend the code it adopts. Any site giving you a confident yes or no for every address in the country is guessing, and you cannot tell which answers are the guesses.

22,662counties and incorporated places that could issue your permit
41%of Americans live where the state code does not settle it
30%of ZIP codes straddle a county line, so even the office is ambiguous

So this does not pretend. Each answer is the typical rule, where it comes from, and the thresholds that would flip it — plus a route to the office that actually decides. How this works.

Permit or Not — do I need a building permit? — Permit or Not