A building permit is a city's record that someone was authorized to do work — a new roof, an addition, electrical, a demolition. Reading the permit history of an address (and its block) is one of the fastest ways to understand a property beyond the listing photos.
What building permits tell you
- What's been done to the house: a recent re-roof, a new furnace, a kitchen gut, or an addition — and when.
- What's happening next door: new construction, demolitions and major renovations nearby, which shape noise, parking and property values.
- Whether work was legal: visible improvements with no matching permit can mean unpermitted work.
How to look up permits for an address
- Find the city's open-data permit portal (most large US cities publish permit issuance), or use a tool that reads it for you.
- Search by the street address or by the block, and set a date range — the last few years is usually enough to see the pattern.
- Read the permit type and description: "alteration," "new construction," "demolition," "electrical," "plumbing," "mechanical."
Agent Neighbor does this step for you in the cities where permits are wired in: it reads the city's permit feed for the block and folds it into the Development score, with each permit dated and linked to the source.
Spotting unpermitted work
This is where permits earn their keep for a buyer. Walk the house with the permit history open:
- A finished basement, a new deck, a converted garage or an added bedroom with no matching permit is worth a direct question.
- Unpermitted work can complicate insurance claims, financing and resale — and it may not meet code.
- It's not automatically a dealbreaker, but it belongs on your inspector's list and in your negotiation.
Reading the pace of a block
A cluster of new-construction and major-renovation permits nearby often signals a neighborhood on the rise — but also years of dust, scaffolding and street closures. A block with almost no permit activity is stable, for better or worse. Either way, it's context the listing won't give you.
Where the data comes from
Building permits are public records. Cities like Philadelphia, Chicago and Austin publish permit issuance as free, keyless open data with coordinates, which is what lets a tool read them by address. Coverage and columns vary by city, so always confirm anything important against the city's own permit record.