San Antonio, TX Environmental Rules: Flood Elevation Requirements (2026)

Chapter 35, Subdivision D of San Antonio's Unified Development Code sets the technical floodplain construction standards enforced citywide within all Special Flood Hazard Areas mapped on FEMA's Flood Insurance Rate Map. Section 35-F141, General Standards, requires new construction and substantial improvements to be anchored against flotation and requires electrical, mechanical, and plumbing equipment such as furnaces, water heaters, and pressure tanks to be elevated or floodproofed to a minimum of one foot above the regulatory floodplain elevation, the city's version of FEMA's base flood elevation.

Section 35-F142, Specific Standards, applies that one-foot freeboard to the building itself: a habitable structure undergoing a substantial improvement, or a structurally disconnected lateral addition, must have its finished floor at least one foot above the regulatory floodplain, and a detached accessory dwelling unit built in the floodplain must clear the same one-foot mark. Nonresidential buildings get a choice under Section 35-F142(b): elevate the lowest floor, including any basement, one foot above the regulatory floodplain, or floodproof the structure watertight to that same level and have a registered professional engineer certify the design to the Floodplain Administrator.

Before the city approves a permit for any of these projects, Section 35-F142(a)(1)(G) requires a pre-construction elevation certificate; before final inspection or certificate of occupancy, Section 35-F142(a)(1)(H) requires a matching post-construction elevation certificate, both built on FEMA's National Flood Insurance Program Elevation Certificate form. The Director of Public Works, acting as Floodplain Administrator under Section 35-F121, reviews and approves every floodplain development permit and can deny habitable construction outright where the site has a history of high-water rescues or repetitive flood losses under Section 35-F142(a)(1)(E).