What matters for project planning
Two of these facts drive structural movement on the coast. The high water table means bearing conditions change seasonally rather than staying constant, and the sandy coastal soils that come with it settle and erode rather than shrinking and swelling the way Piedmont clay does — a different mechanism from most national foundation guidance. Current flood mapping matters separately: inside a mapped zone, work extensive relative to the structure's value can engage additional requirements, and in a local historic district exterior drainage work can attract review of its own.
Official sources
Verify the property, not just the city
Citywide Wilmington data doesn't establish anything for one specific lot. Flood-zone status, historic designation, drainage requirements, soil conditions, and existing below-grade construction all need parcel-level confirmation before work begins.
Sources reviewed June 20, 2026. External requirements and maps can change.