Do I need a permit?
Answer a few questions about your project and get a clear read on whether a permit applies, plus a direct link to the office that decides.
What this tool does and does not do. It reasons over general US building-code practice and routes you to your own jurisdiction's official page. It does not know your local exemption thresholds, fee amounts or review times, and it does not invent them. The office with jurisdiction is the only authority on those.
How this tool decides
It checks your project against the categories that trigger a permit essentially everywhere in the United States: structural change, new footprint, electrical or plumbing that moves, mechanical replacement, roofing, change of use, and the specific categories that carry their own permit type such as pools, retaining walls and solar.
What it deliberately does not do is guess your local exemption thresholds. The shed size that triggers a permit, the fence height, the repair value below which a jurisdiction does not care — those numbers are set locally and differ between neighbouring jurisdictions. That is the one part of this question a national tool genuinely cannot answer, so it routes you to the office that can.
The underlying principle
Permitting exists so that someone independent verifies work will not fall down, burn, flood, leak or electrocute anyone, and so a record survives for the next owner. Most edge cases resolve if you ask which of those risks your work changes. Swapping a light fixture on an existing circuit changes none of them. Adding a circuit changes one.
Why guessing wrong is expensive
A work-without-permit penalty is commonly a doubling of the permit fee. Concealed work has to be exposed for inspection at your cost. Insurers can deny claims that trace back to unpermitted work. Appraisers exclude unpermitted square footage. And unpermitted work found during a buyer's inspection is discovered at the worst possible moment, under time pressure, with the buyer holding the leverage.
Our full guide goes through each project category and what happens if work has already been done.