Tomball, TX Accessory Structures: ADU Rules (2026)

Tomball's Chapter 30 (Zoning) establishes permitted uses in residential districts. Standard single-family residential districts (R-1, R-2, R-3) typically limit each lot to one principal dwelling unit. Accessory structures such as detached garages, workshops, and storage buildings are permitted, but a separate dwelling unit with independent kitchen and bathroom facilities is generally not allowed as an accessory use. Converting a garage, detached building, or portion of a home into a self-contained living unit with a separate kitchen constitutes creating a second dwelling unit, which requires the lot to be in a zoning district that permits multi-family or duplex use. Property owners seeking to build an ADU may apply for a zoning variance through the Board of Adjustment or request a specific use permit if the zoning ordinance provides for one. Planned developments and planned unit developments may include provisions for ADUs as part of their development agreements. Texas does not have a statewide ADU mandate similar to California or Oregon, so cities retain full control over ADU policy. Some Texas cities have adopted ADU-friendly ordinances, but Tomball has not taken this step. Detached buildings that serve as guest quarters without full kitchen facilities (no stove or oven) may be classified as accessory structures rather than dwelling units and are subject to standard accessory structure setback and size requirements.