San Antonio’s Unified Development Code distinguishes detached accessory dwellings from attached units and sets different lot-line rules. These selected figures are tied to the listed district and form conditions.
Local standards
The selected local standards are summarized in the San Antonio Unified Development Code §35-371 — Accessory Dwellings. In single-family districts other than FR, living area is the greater of 800 square feet or 50% of primary structure GFA, with a 1,600-square-foot ceiling. The FR subsection gives a separate 1,200-square-foot limit. A detached unit must be in the rear yard; one is allowed per lot. Height is limited to 25 feet or two stories.
Confirm the applicable rule
A detached unit generally needs five feet from side and rear lot lines, but may be three feet away if it has no overhang. An attached unit follows the principal structure’s required setbacks under the underlying district. Check the current UDC use matrix, district, height measurement, and parking trigger, especially when an ADDU exceeds 800 square feet. Zoning measurements do not by themselves establish fire separation, building-code compliance, utility capacity, or permit approval. For shared measurement methods, see the setback and separation guide and floor-area guide.
