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

Unincorporated Washington County does not require a building or electrical permit for new construction or an addition to an existing structure¹. That does not clear every permit: a floodplain permit, an OSSF (septic) permit, a driveway culvert permit, a utility-right-of-way permit, and a subdivision application or variance letter can each still apply depending on the project¹. City limits change the answer. Brenham follows the 2021 International Building Code suite and the 2020 National Electrical Code, effective October 1, 2024⁵. Burton adopted the 2015 International Building Code and International Residential Code, although its ordinance deletes city permit and inspection provisions and puts compliance on the builder⁶. Confirm the parcel's jurisdiction before relying on the unincorporated-county permit exemption.

Because the county requires no building permit on unincorporated land, an owner can build their own home without an owner-builder exemption, though state licensing for electrical, plumbing and HVAC work may still apply¹.

Washington County Engineering and Development Services issues driveway (culvert) permits, subdivision applications and utility-right-of-way permits, and its Road and Bridge division maintains county roads and bridges¹. Reach that office at 979-277-6275, 3650 State Highway 36 N, Brenham, TX 77833-3753, or by email at wcrboffice@washingtoncountytx.gov¹. Washington County Environmental Health, a division of the same department, administers floodplain permits and septic (OSSF) permits and can be reached at 979-277-6290, 3650 Highway 36 North, Brenham, Texas 77833^3,8. Both offices share the same Highway 36 North complex in Brenham but handle different permits, so match your project to the right one before you call^1,8. The county's published fee schedule lists a floodplain determination permit at $325.00 for single-family residential use and residential driveway permits at $625.00 for 20 to 30 feet wide and $875.00 for 31 to 40 feet wide⁹.

Unincorporated Washington County has no county zoning ordinance, because Texas law gives zoning authority only to municipalities, not counties, outside a short list of specific, narrowly defined places elsewhere in the state^2,8. The City of Brenham is different: its Planning office handles zoning issues within the city⁷. Burton's building-code ordinance also sets a 750-square-foot minimum heated area for a residence, with smaller proposals subject to City Council consideration⁶. On unincorporated land, the county sets no zoning-based minimum lot size, setback, lot-coverage, building-height or minimum-home-size rule². Subdividing land remains regulated separately: dividing a tract into two or more parts outside an incorporated city requires an approved plat or a variance letter¹.

Washington County Environmental Health administers on-site sewage facility (septic) permitting throughout the county, except in an area already regulated under another order, ordinance or resolution³. Every new, altered, repaired or enlarged system needs a permit before work begins, regardless of acreage; routine maintenance such as tank pumping does not³. All septic construction must pass a county inspection before it is covered, with the inspection scheduled at least 24 hours ahead¹⁰. After installation, systems using secondary treatment or drip irrigation need regular inspections by a valid maintenance company on the permitting authority's schedule; we could not confirm that every conventional system needs periodic inspection¹¹. Only about 5.3% of Washington County soils lack severe limitations for a conventional drain field, so arrange a site evaluation before committing to a house site¹². Floodplain development separately requires county authorization before work begins⁴.

On unincorporated land, RV, tiny-home and manufactured-home occupancy are unrestricted by Washington County zoning because the county has no zoning authority². That zoning answer does not waive wastewater rules. A new, altered, repaired or enlarged septic system requires a permit before work begins regardless of acreage³. Sewage holding tanks must meet state standards and cannot serve a property with more than one dwelling, RV or similar sewage-producing structure; the restriction does not apply to an RV using only its factory-installed integrated wastewater tank³. Washington County's order does not confirm the rules for composting toilets or graywater, so ask Environmental Health before choosing either arrangement⁸. Inside Brenham, city zoning and adopted building codes apply instead of the unincorporated-county answer^5,7.

1. Confirm your parcel's jurisdiction; the county permit exemption applies to unincorporated land, while Brenham and Burton have adopted building codes^1,5,6.
2. Check the flood map and obtain written authorization from Washington County Environmental Health before beginning floodplain development^4,8.
3. Apply through Environmental Health before installing, altering, repairing or enlarging an OSSF, regardless of acreage; schedule its construction inspection at least 24 hours ahead^3,8,10.
4. If the driveway fronts a county-maintained road, obtain a culvert permit from Engineering and Development Services¹.
5. If you are dividing a tract into two or more parts outside a city, submit a plat or variance letter unless the agricultural, ranching, wildlife-management or timber-production exemption applies^1,13.
6. On unincorporated land, no county zoning review sets minimum home size, setbacks, lot coverage or building height².

Washington County averages 43.7 inches of rain a year and has spent roughly 20.5% of years in severe drought, more rain than most of Texas but still worth confirming your water source¹². Only about 5.3% of the county's soils are free of severe limitations for a conventional septic drain field, even though all of the county's land sits at 15% slope or less, so flat ground here does not guarantee an easy septic site¹². Federal land covers only 2.6% of the county, so nearly all of Washington County is private¹². The county's effective property tax rate is about 1.1%, with a median property tax bill of $3,105 a year¹². From the county's center, the nearest city of 100,000 or more is roughly 27 miles away, and Washington County has 61.3 people per square mile¹². If you plan a short-term rental outside city limits, Washington County charges a 7% Hotel Occupancy Tax that includes short-term rentals, collected quarterly¹⁴.