Unincorporated Area Rules
Building Outside City Limits Requires a County Development Permit
Land outside any city's limits in Jefferson County is called unincorporated. You still need county permits to build there, and floodplain rules apply to much of the county.
If you buy land outside the city limits of Beaumont, Port Arthur, Groves, Nederland, Port Neches, or other cities, your land is in unincorporated Jefferson County. The county has its own subdivision and floodplain rules for those areas. You need a development permit before you build.
Flooding is a real risk in Jefferson County. Much of the county is low-lying and near the coast. The county's rules address those risks.
Before you build, contact the Jefferson County engineering department. Get the current subdivision and floodplain requirements from them.
You can also look up your parcel's FEMA flood zone at msc.fema.gov. If your land is in a regulated flood zone, you may need flood insurance or must build at a certain height.
Source to confirm: Jefferson County — Subdivision and Floodplain Regulations