Building permits, zoning and septic rules in Somervell County, Texas

Unincorporated Somervell County appears to have no building department and no building-permit requirement for ordinary construction: the county's own site addresses on-site sewage permitting but nothing broader, and we could not find a county ordinance establishing general building permits, so confirm with the OSSF office or Commissioners Court before you start¹. Texas gives some large counties authority to adopt a fire code covering commercial buildings, public buildings and multifamily dwellings of four or more units in unincorporated areas, but only for a county with a population over 250,000 or adjacent to one — Somervell County's own population, about 9,888, is far below that threshold^8,9. Inside the incorporated City of Glen Rose, a separate building-permit and zoning process applies, run by the city rather than the county¹. If you're placing a factory-built or modular unit rather than site-building, Texas's Industrialized Housing and Buildings program sets statewide construction-code standards for those units wherever you build¹⁰.

There's no county building department to contact, but three offices matter for rural land in Somervell County¹. Septic (OSSF) permits go through the county's On-Site Sewage Facility office in Glen Rose, which also serves as the county's Floodplain Administrator¹. County road and driveway questions for county-maintained roads go to Road & Bridge Maintenance, also based in Glen Rose¹¹. New subdivisions outside Glen Rose need Commissioners Court approval of the plat, with the County Health Unit's Designated Representative — the same OSSF office — reviewing the plat for sanitation before that happens⁴.

Unincorporated Somervell County has no zoning: Texas counties don't have general zoning power, and Somervell County has not adopted a zoning ordinance for its unincorporated area³. Because the county has no zoning authority here, it sets no minimum dwelling size, no setbacks, no lot-coverage limit and no building-height limit for unincorporated land, and it publishes no zoning districts². That's different from the incorporated City of Glen Rose, which does zone within its own limits and regulates uses like manufactured homes district by district¹². Even without zoning, a new subdivision outside Glen Rose still has to meet the county's own lot-size rules: 2 acres net per lot where it will use on-site sewage, or 1 acre net per lot where it will have public water⁴.

Septic systems (OSSFs) in unincorporated Somervell County are permitted by the county itself, acting as the state's authorized agent, through the On-Site Sewage Facility office in Glen Rose^1,4. Almost every OSSF needs a permit before construction, installation, repair or extension, for a new house or a replacement of a failed system alike⁵. Texas does carve out an exemption for larger tracts: a single-family home on at least 10 acres can skip the OSSF permit if a licensed site evaluator confirms no nuisance or groundwater-pollution risk, every part of the system sits at least 100 feet from the property line, effluent stays on your property, and the house is the only dwelling on the tract¹³. Soils here are a mixed bag: about 19.1 percent of Somervell County's soils are free of severe limitations for a conventional septic drain field, so plenty of land will perk, but plan on a site evaluation before you assume yours will⁸.

Water supply has its own permit: all non-exempt wells in Somervell County must get a permit from the Prairielands Groundwater Conservation District, and a new well gets an Operating Permit⁶.

Because unincorporated Somervell County has no zoning ordinance, the county places no zoning-based restriction on living in an RV, a tiny home or a temporary camping setup on your own unincorporated land, and the same is true for adding an accessory dwelling². That's a real answer, not just an absence of information: Texas law simply doesn't give the county zoning power to restrict those uses here². It isn't a blanket exemption from everything else, though. Any habitable structure, an RV included if you're living in it full time, still needs a wastewater system that meets state and county OSSF rules, and a new lot created for that purpose has to meet the county's minimum lot-size chart⁴. This guide could not confirm a county short-term-rental rule, so if you plan to rent the RV or tiny home out rather than live in it yourself, check with the county directly¹.

First, confirm your parcel is outside the City of Glen Rose, since inside city limits you'd need a city building permit and follow city zoning instead of the rules in this guide¹. Second, contact the county's On-Site Sewage Facility office early for your septic permit; almost every OSSF needs one before construction starts, unless your home sits on 10 acres or more and meets Texas's site-evaluation exemption conditions^1,5,13. Third, if you're creating a new lot rather than buying an existing platted one, get Commissioners Court approval of your plat before construction begins; fees run $350 plus $10 per lot for a 1-5 lot subdivision, and the Court has 30 days to act⁴. Fourth, size your lot to the chart: 2 acres net per lot with on-site sewage, or 1 acre net per lot with public water⁴. Fifth, if your driveway will connect to a state highway, submit TxDOT Form 1058 to the local district office and get your permit before any construction on the right of way⁷. Finally, ask the county's Floodplain Administrator — the same OSSF office — whether your land sits in a mapped flood zone before you build¹.

Somervell County is gentle and largely private: 91.4 percent of the county sits at 15 percent slope or less, 40.1 percent is wooded, and none of the county is federal land, so most of what you see on a map is potentially buildable and privately held⁸. Water is a real constraint: the county averages only about 35.8 inches of rain a year and has been in severe drought roughly 29.8 percent of years, so a private well's yield, its Prairielands Groundwater Conservation District permit and any surface-water rights are worth checking before you buy^6,8. At about 9,888 people and 53.1 people per square mile, Somervell is more settled than many rural counties, and the nearest city of 100,000 or more is about 47 miles away⁸. Property taxes run a bit higher than many rural counties, with an effective rate near 1 percent and a median annual bill around $2,452 against a typical home value near $416,622⁸.