5 county-level rules, plus city-specific rules for 2 cities in Williamson County, Texas.
Verified from official government sources
Texas counties cannot zone, so unincorporated Williamson County sets no ADU size, setback, or occupancy limit. An accessory dwelling with plumbing requires an on-site sewage (OSSF) permit under Health & Safety Code Chapter 366.
Tex. Health & Safety Code §366.051(a)
A person must hold a permit and an approved plan to construct, alter, repair, extend, or operate an on-site sewage disposal system.
Unincorporated Williamson County does not zone or permit storage sheds. No county size, height, or setback rule applies. HOA deed restrictions govern placement, size, and appearance.
Unincorporated Williamson County neither zones nor permits garage conversions. Converting a garage into living space with a bathroom triggers an on-site sewage (OSSF) review under Health & Safety Code Chapter 366.
Tex. Health & Safety Code §366.051(a)
A person must hold a permit and an approved plan to construct, alter, repair, extend, or operate an on-site sewage disposal system.
Unincorporated Williamson County does not zone or permit carports. No county setback, height, or size rule applies. HOA deed restrictions and utility easements govern placement.
A tiny home on wheels is titled as a travel trailer under Texas Transportation Code Section 501.002 and is not used as a permanent dwelling. A tiny home on a foundation with plumbing needs an OSSF septic permit.
Tex. Transp. Code §501.002(30)
is designed primarily for use as temporary living quarters in connection with recreational, camping, travel, or seasonal use; ... is not used as a permanent dwelling
2 cities in Williamson County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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Williamson County Ordinance Hub →