Brazos County, TX Accessory Structures: ADU Rules (2026)

Under Texas Local Government Code §233.153, a county may adopt building-code standards (referenced to the IRC) for new single-family houses and duplexes in unincorporated areas, but the same statute expressly states that a county may not require prior approval before new residential construction begins, may not adopt or enforce zoning regulations under that subchapter, and may not charge a fee to defray enforcement costs. As a result, Brazos County does not issue residential building permits, does not restrict accessory dwelling unit (ADU) size, height, or owner-occupancy, and does not require ADU registration in unincorporated territory. Inside the City of College Station, ADUs (called Accessory Living Quarters) are permitted accessory uses in most residential zoning districts subject to size limits and parking requirements set in the College Station Unified Development Ordinance. Inside the City of Bryan, ADUs are governed by the Bryan Land Development Ordinance and may require special permits depending on zoning district. Septic systems serving any new ADU on private wastewater outside city limits must be permitted by the Brazos County On-Site Sewage Facility (OSSF) program under 30 TAC Chapter 285, and floodplain development permits are required from Brazos County for any structure in a FEMA Special Flood Hazard Area.