5 county-level rules, plus city-specific rules for 1 city in Galveston County, Texas.
Verified from official government sources
Texas counties cannot zone, so unincorporated Galveston County sets no ADU rule. Inside the City of Galveston, one ADU is allowed per residential lot only if a principal building exists, and it cannot exceed the main home's floor area.
City of Galveston LDR Sec. 2.303
An accessory dwelling unit (ADU) is allowed only on a lot with a principal building. A manufactured home, recreational vehicle, travel trailer, or camper shall not be used as an ADU. An ADU shall be subordinate to the principal structure and shall not exceed the total floor area of the principal building.
The county cannot set shed setbacks. In the City of Galveston, accessory structures must sit 3 feet from side and rear lines (0 to an alley) and 6 feet from any habitable structure. League City requires a permit for sheds over 200 square feet.
City of Galveston LDR Sec. 3.305.A
Accessory structures must meet the following setbacks: 3 feet from the side property lines or in accordance with Article 3 Addendums, whichever is more permissive; 3 feet from the rear property line or 0 feet to an alley or right-of-way; and 6 feet from any habitable structure.
The county cannot zone conversions. In the City of Galveston, an accessory building may not be occupied as living space unless it was constructed and approved for residential use, so a garage-to-living-space conversion needs city permits and inspection.
City of Galveston LDR Sec. 2.401.F
Residential occupancy shall not be permitted in accessory buildings that are not constructed and approved for residential use.
The county cannot zone carports. In the City of Galveston, a detached carport is an accessory structure and must meet the Sec. 3.305 setbacks: 3 feet from side and rear lines (0 to an alley) and 6 feet from any habitable structure.
City of Galveston LDR, Definitions (Accessory Building)
Examples of residential accessory buildings and structures include storage sheds, gazebos, home workshops, children's playhouses, greenhouses or other garden shelters, and detached residential garages and carports.
The county cannot zone tiny homes. In the City of Galveston, a tiny house on wheels counts as an RV or travel trailer and cannot be used as a dwelling or ADU; a permanent-foundation tiny house must meet full residential building code.
City of Galveston LDR Sec. 2.303.A.1
A manufactured home, recreational vehicle, travel trailer, or camper shall not be used as an ADU. An ADU shall be of similar construction materials as the principle building.
1 cities in Galveston County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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