Development Rules
Building outside city limits in Hays County still requires county permits
If you want to build or develop land in the unincorporated parts of Hays County, you must get approval from the county's Development Services department.
Not all land in Hays County is inside a city. Land outside city limits is called unincorporated. The county requires permits for any construction or development on unincorporated land. That includes clearing land, putting up structures, or splitting lots.
Land inside a city follows that city's rules, not the county's. Some land sits in a city's ETJ — short for extraterritorial jurisdiction. That is the zone just outside city limits where the city may also have a say over development. Before you buy rural land or start a project, check with Hays County Development Services at hayscountytx.gov to find out which rules apply to your parcel.
Source to confirm: Hays County — Development Services