ADU Rules in San Antonio, Texas

Overview

San Antonio is Texas's second-largest city, with approximately 1.5 million residents in Bexar County. As a home rule charter city, San Antonio has broad authority to regulate land use through its Unified Development Code (UDC). There is no Texas statewide ADU preemption law — local zoning rules fully govern ADU construction.

San Antonio's development environment is shaped by two major factors unique to the city: an enormous military presence (Joint Base San Antonio) and a rich historic preservation tradition centered on the San Antonio Missions and River Walk area.

Zoning Districts and ADU Permissions

San Antonio's Unified Development Code divides the city into residential zoning districts. Accessory dwelling units are permitted in most single-family districts, though the specific standards vary:

• R-20, R-6, R-4 and other single-family residential districts: ADUs (also called secondary units or casitas) are commonly permitted, with specific standards set by the UDC; check the district description for your parcel
• Detached ADUs must be located on the same lot as the primary dwelling
• ADUs may not be subdivided or sold separately from the primary residence
• Owner-occupancy requirements may apply depending on the district
• Short-term rental licensing is a separate requirement from ADU approval

Key Development Standards

Standard development requirements for ADUs under the UDC include:

• Maximum size: Typically 50% of the primary dwelling's gross floor area for attached units; detached ADUs have separate square footage limits by district
• Height: Generally limited to one story or 20–25 ft for detached structures in residential zones
• Setbacks: Rear yard 5 ft minimum; side yard 5 ft minimum for detached ADUs; front yard setback same as primary structure
• Lot coverage: Total impervious cover limits apply; typical single-family lots have 45–55% maximum coverage
• Parking: One additional off-street parking space is typically required for the ADU

JBSA AICUZ: The Critical Military Overlay

Joint Base San Antonio (JBSA) is one of the largest military installation complexes in the United States, comprising Lackland AFB (west side), Randolph AFB (northeast), Kelly Field Annex (southwest), and Camp Bullis (northwest). The combined AICUZ (Aircraft Influence Compatible Use Zone) footprint covers vast portions of San Antonio.

The AICUZ includes:

• Noise Contour Zones (65, 70, 75+ decibel day-night average sound level): New residential construction is increasingly restricted in higher noise zones; 75+ dB zones generally prohibit new residential units
• Accident Potential Zones (APZ I and APZ II): Safety zones extending beyond runways where residential construction is restricted or prohibited
• Clear Zones: Immediately adjacent to runways; no habitable structures permitted

If your property is near Lackland, Randolph, Kelly Field, or Camp Bullis, check with the City of San Antonio Development Services Department before designing any ADU. The JBSA compatibility maps are available through the city and through the base's public affairs office.

Historic Preservation Considerations

San Antonio has significant historic districts including the area surrounding the San Antonio Missions (a UNESCO World Heritage Site), the King William Historic District, and Tobin Hill. Properties in these districts must obtain a Certificate of Appropriateness from the Historic and Design Review Commission (HDRC) before constructing any new structure, including ADUs. Design standards in historic districts are strict and apply to materials, massing, and siting.

Flood Risk

San Antonio is situated on the Balcones Escarpment, making it vulnerable to flash flooding from the Guadalupe, Medina, and San Antonio Rivers. The city has invested heavily in the San Antonio River improvements, but many areas still lie within FEMA Special Flood Hazard Areas. Check FEMA flood maps and obtain a floodplain development permit if required before building an ADU.

Permit Process

1. Verify zoning district and AICUZ overlay at sanantonio.gov/DSD
2. Pre-application meeting with Development Services recommended for complex sites
3. Submit building permit application with site plan and construction drawings
4. Plan review by Development Services (zoning, building, fire)
5. Separate permits for electrical, plumbing, mechanical
6. Required inspections through certificate of occupancy

Contact

• Development Services Department: sanantonio.gov/DSD | 210-207-1111
• JBSA AICUZ Information: jbsa.mil
• Historic and Design Review Commission: sanantonio.gov/HDRC

Disclaimer: ADU regulations in San Antonio, including JBSA AICUZ boundaries, are subject to change. This page provides general guidance only. Always verify current regulations with the City of San Antonio Development Services Department and consult a licensed Texas professional before proceeding.