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Data notes
Data sources & limitations
PermitPipe organizes public building-permit filings from Maryland county and city open-data feeds and public permit portals. We do not buy data, scrape behind logins, or guess at numbers. This page explains where each county's data comes from, how fresh it is, what's missing, and what governments simply do not publish.
Where the data comes from
| County | Source | Refresh | Declared value? |
|---|
| Montgomery | dataMontgomery (county open data) | Daily | Yes |
| Baltimore City | Open Baltimore (county GIS) | Daily | Yes |
| Baltimore County | Baltimore County GIS | Daily | Often missing |
| Anne Arundel | County permit portal (Accela) | Daily | No |
| Howard | County permit portal (Accela) | Daily | No |
| Carroll | County permit portal (Accela) | Daily | No |
| Washington | County permit portal (Accela) | Daily | No |
| Frederick | County GIS | Daily | No |
| Prince George's | County open data + planning extract | Currently delayed (see gaps) | Partial |
What "complete" looks like (expected volume)
Each source has an expected monthly volume based on its own recent history. If a county publishes materially less than this, it's a flag for us to investigate before the data reaches you.
| County | Typical filings / month |
|---|
| Anne Arundel | ~3,900 |
| Baltimore City | ~3,000 |
| Howard | ~1,600 |
| Prince George's | ~975 (real flow; currently delayed) |
| Baltimore County | ~700 |
| Carroll | ~640 |
| Montgomery | ~600 |
| Washington | ~500 |
| Frederick | ~40 (one permit category only) |
Known gaps
- Prince George's: the county stopped publishing its full permit feed after March 31, 2026 when it moved to a new permitting system. Roughly 5,500 permits since April 2026 aren't published anywhere public yet; we've filed a records request for a current feed. Until then, PG volume in the app is legacy-only.
- Anne Arundel & Howard: recent flow is complete; deeper history is still being loaded.
- Frederick: the county's public data covers one narrow permit category (~40/month), not all construction activity.
- Not yet covered: Harford, Charles, St. Mary's, Calvert, Cecil, Talbot, Dorchester, Caroline, Garrett, Allegany, Kent, Somerset, Wicomico, Worcester, Queen Anne's. Some publish no machine-readable data at all; others are on the roadmap.
- Bulk filings: counties sometimes issue dozens of permits for one address on one day (e.g., batch approvals). Those are real, distinct permits, and counts will reflect them.
- Data-entry quirks: future-dated typos (e.g., year 9005) and test records appear in raw government data; we filter obviously corrupt dates.
What government does not give us
- Declared job value — missing from Carroll, Washington, Anne Arundel, Howard and Frederick. Where it exists it is applicant-declared, not verified cost.
- Contractor and owner names — only Baltimore County and parts of Baltimore City publish them.
- Status / final-inspection dates — partial or absent for several counties; PG's legacy feed has none.
- Map coordinates — only Baltimore City, Baltimore County and PG publish them.
- Bulk exports or APIs — most counties offer only web search or PDF reports; some cap exports (Howard at 100 rows), and PG's new system is login-gated.
- Real-time updates — publication lag ranges from 1 to 30+ days depending on county; there is no real-time feed anywhere.
How we handle it
- Records are de-duplicated by permit number within each county. The same work can still appear twice if two different government systems publish it under different numbers.
- Every source is polled daily and has an expected-volume baseline plus a live connection check. If a source slows, stops, or errors, it's flagged for investigation before the published data is regenerated.
- Fields are normalized (dates, addresses, trades) but addresses are reproduced as published — unit numbers and formatting vary by county.
- Nothing here is a credit report, title search, or legal record. For official records, use the county source linked on each permit.