5 county-level rules, plus city-specific rules for 1 city in Williamson County, Tennessee.
Verified from official government sources
Tennessee sets no statewide ADU mandate, so a second or accessory dwelling in unincorporated Williamson County is controlled entirely by the county Zoning Ordinance and your residential district. A building permit and septic approval are required where one is allowed.
Small backyard sheds in unincorporated Williamson County are permit-exempt, but the Building Codes Department requires a permit for larger accessory buildings and for any structure on a permanent foundation. Sheds must meet zoning setbacks and the 20-percent lot-coverage cap.
Williamson County, TN, Zoning Ordinance Sec. 23.04 (Accessory Uses)
Accessory uses shall not cover more than twenty (20) percent of the lot area.
Converting a garage into living space in unincorporated Williamson County is a change of occupancy that requires a building permit. The new room must meet the adopted residential code for egress and for smoke and carbon-monoxide alarms.
A carport is a roofed accessory structure in unincorporated Williamson County, so it needs a building permit from the Building Codes Department and must meet zoning setbacks and the 20-percent accessory-use coverage cap.
A tiny home's status in unincorporated Williamson County turns on its foundation. On a permanent foundation it is a dwelling under the adopted residential code; on wheels it is a titled RV that zoning does not treat as a permanent home.
1 cities in Williamson County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
See every category we cover for Williamson County — parking, noise, fences, fires, animals, pools, and more.
Williamson County Ordinance Hub →