Building permit data: open-data portals, APIs and databases by state

Permit data sources by city

Most permit data in the US is public and free, the hard part is that every jurisdiction publishes it differently. Big cities run modern open-data portals (many on Socrata or ArcGIS) with daily updates and APIs; smaller ones publish CSVs or nothing at all. Here's where the major markets stand.

Building permit APIs: city endpoints and national databases

Individual permits come from each city's own endpoint. Four API families cover almost every portal: Socrata, ArcGIS, CKAN and Carto; the patterns for each are below. National databases sit on top of those feeds, either as counts or as paid aggregation.

National building permit databases

FieldClients reads the city portals directly and matches each permit to the owner or manager and a verified decision-maker; our per-area coverage by record type is on the markets page.

How to find permit data for a city that isn't listed

Most US municipalities publish permits somewhere; the work is knowing what to look for. Four patterns cover almost everything:

• Socrata. If the portal URL looks like data.cityname.gov and pages have an "API" button, it is Socrata. Every dataset has a four-by-four identifier and a JSON endpoint at /resource/<id>.json, with SoQL query parameters for filtering by date and type. The best case: queryable, documented, usually daily.
• ArcGIS. Common for cities that run permits through their GIS department. Look for /arcgis/rest/services/ in the URL. Query with ?where=1=1&outFields=*&f=json, and check returnCountOnly=true first to size the dataset before pulling it.
• CKAN. Used by a handful of larger cities. Endpoints sit under /api/3/action/package_search, and the actual data is usually a linked CSV rather than a live query API.
• Plain files, or nothing. Many mid-size cities post a CSV or an Excel export on a department page, updated monthly at best. Some publish nothing at all and answer public-records requests instead, which is legal but useless for weekly prospecting.

Two things to check before trusting any source: the actual update frequency (a portal can look live and carry data three months stale) and whether the owner field is populated, because a permit with a blank owner is only half a signal.

What permits do, and don't, tell you

A permit is a dated commitment to real work: it names an address, a type of work, a filing date, and usually an applicant. That's a genuine buying signal for the trades and suppliers who serve a project. What a permit doesn't include is the one thing you need to win the work: the decision-maker at the account and a verified way to reach them. Closing that gap, matching the filing to the owner, finding the person who signs, and verifying their contact, is the enrichment step.

DIY vs a daily feed

Everything above is public, and you can pull it yourself: open the portal, filter by type and recency, cross-reference ownership. What that produces is a list, and the list is the smallest part of winning work, even in a single market. Three gaps decide the outcomes:

• Freshness beats coverage. A permit is worth the most the week it's filed and decays from there, so a one-time pull starts rotting the day you make it. The value is in checking every source every day, including the weeks your crews are slammed, which is exactly when a manual process dies.
• One source is half a signal. A permit alone says work is happening. The same address joined to its violations, registrations, and managing-agent history says who's buying, why now, and what the account behind it is worth. Even one market means several sources with different schemas that have to agree on the same building.
• Enrichment quality is where outreach lives or dies. The filing names an applicant or an owner LLC, not the person who signs. Matching the record to the account, finding the decision-maker, and verifying the contact is the skilled step; one email to a name that left two years ago burns the account. Our standard: verified decision-maker email on every reveal, company phone where listed.

That is what the FieldClients feed does for each market: the same public record, checked daily, joined into account stories. Contacts are verified before a reveal returns them.