San Antonio building & ADU permits

Texas has no statewide zoning or ADU mandate, so accessory-dwelling rules are set city-by-city; a 2025 statewide ADU-by-right bill did not become law. Austin's HOME reforms now allow up to three units on most single-family lots.

Reform is local: Austin's HOME initiative cut minimum lot sizes and allowed more units per lot, while 2025 state laws eased lot-size minimums and commercial-to-residential conversions.

San Antonio permits accessory dwelling units — internal, attached, and detached — by right in many residential zoning districts under its Unified Development Code (Section 35-371). Texas has no statewide ADU mandate, so the city's local rules govern, and a 2022 package of nearly 200 UDC amendments (effective January 1, 2023) was designed in part to make ADUs easier to build.

A detached accessory dwelling is generally limited to 800 square feet or 50 percent of the primary structure's gross floor area, up to a maximum of 1,600 square feet in most single-family districts (and 1,200 square feet in the 'RE' district). One on-site parking space is required only when the ADU exceeds 800 square feet. Unlike many cities, San Antonio retains an owner-occupancy requirement: the owner must live in either the principal home or the ADU as a permanent residence, may not collect rent on the owner-occupied unit, and records an affidavit or covenant confirming residency — a rule the city reaffirmed in its recent amendments to keep ADUs as long-term housing rather than short-term rentals.

A code-compliant ADU requires an accessory dwelling permit and is handled through the building-permit process; the city's Information Bulletin 402 details the district-specific standards.

This is an informational summary — verify current rules with the city's planning/permitting department; not legal advice.

See also: Texas ADU law and what is an ADU?