Garland, TX Environmental Rules: Flood Elevation Requirements (2026)

Under § 31.104(B), once base flood elevation data exists for a site, whether from the FEMA Flood Insurance Study, the floodplain administrator, or a subdivision engineering study, every new residential structure and every substantial improvement to an existing one must have its lowest floor, including any basement, at least two feet above the base flood elevation, a full foot higher than the National Flood Insurance Program's one-foot minimum (§ 31.100(C)(7)). All associated machinery and equipment, including the electrical, heating, ventilation, plumbing, and air-conditioning systems required under § 31.104(A)(4), must clear the base flood elevation by at least one foot.

Nonresidential buildings have an alternative: they can either meet the same two-foot freeboard or be engineered watertight and floodproofed below that level, with a professional engineer's certification kept on file recording the specific floodproofed elevation (§ 31.104(B)(2)). Manufactured homes placed in zones A1-30, AH, or AE must sit on a permanent foundation with the lowest floor two feet above base flood elevation and be anchored against flotation (§ 31.104(B)(4)). Enclosed areas below the elevated lowest floor that can flood must include at least two openings totaling one square inch of net area per square foot of enclosed space, with the bottom of each opening no higher than one foot above grade, so floodwaters can pass through automatically (§ 31.104(B)(3)).

In the AO and AH shallow-flooding zones, structures instead must clear the highest adjacent grade by the FIRM's stated depth number plus one foot, or three feet if no depth is shown (§ 31.104(D)).