Easy lot to build on, with one specific watch-item: expansive clay. The site is well outside any FEMA flood zone, the slope is a friendly 3%, no wetlands, no nearby streams. Houston Black clay (and similar Vertisols across DFW) shrinks and swells with moisture changes — it's the reason every Dallas-area home has slab cracks if it isn't built right. Specify a properly designed post-tensioned slab with adequate moisture conditioning, install root barriers near foundation trees, and you'll be fine. Standard infill construction; no surprises beyond the well-known clay issue.
| Layer | Finding | What it means |
|---|---|---|
| FEMA flood zone | Zone X (unshaded) | Outside 500-yr floodplain. No flood insurance required. |
| Wetlands (NWI) | None within 1,000 ft | No mapped wetlands. No USACE concerns expected. |
| Soil (SSURGO) | Houston Black clay | Hydrologic group D. PI 35–55. Highly expansive — foundation must accommodate movement. |
| Slope | 3% | Gentle — easy site grading, normal driveway design. |
| Elevation | 670 ft | Typical North Texas plateau elevation. |
| Streams (NHD) | Nearest 1,800 ft | No riparian setback issues. |
| Land cover | Developed, medium intensity | ~55% impervious neighborhood. Standard suburban storm sewer. |
| Design rainfall | 100-yr / 24-hr: 9.3 in | Typical North Texas. Local code drainage handles this scale. |
Implications: Houston Black is one of the most expansive soils in the U.S. Foundation movement is the single largest construction-defect category in DFW residential. Mitigation that works: post-tensioned (PT) slab properly engineered for the site, pre-construction moisture conditioning of the building pad, perimeter moisture barrier (root barrier + mulched bed), and careful tree placement (large trees within 20 ft of foundation are a known risk).
Don't: use a conventional rebar slab without engineering, plant water-thirsty trees adjacent to the foundation, or allow downspouts to discharge against the foundation. All three are how slab failure happens here.
Implications: Standard suburban infill drainage. Lot will tie into existing public storm sewer. Yard grading should slope away from the foundation at 5% minimum for the first 10 ft (Texas Section 1804 of IRC). No on-site detention typically required for a single-family lot.
| Duration | 2-yr | 10-yr | 25-yr | 100-yr |
|---|---|---|---|---|
| 15-min | 0.78" | 1.18" | 1.42" | 1.79" |
| 1-hr | 1.65" | 2.62" | 3.21" | 4.13" |
| 24-hr | 3.91" | 6.18" | 7.54" | 9.34" |