The National Flood Insurance Program and the County Code require that all structures within a designated 100 year flood zone (Flood Zone A, AE or AO) be brought into compliance with current building standards if there is substantial damage to the structure, regardless of the cause, or if substantial improvements are added. They are defined as follows:
- "Substantial damage" means damage of any origin sustained by a structure whereby the cost of restoring the structure to its before damaged condition would equal or exceed 50% of the market value of the structure before the damage occurred.
- "Substantial improvement" means any reconstruction, rehabilitation, addition, or other proposed new development of a structure, the cost of which equals or exceeds 50% of the market value of the structure before the "start of construction" of the improvement. This term includes structures which have incurred "substantial damage", regardless of the actual repair work performed.
Requirements for a structure to be in compliance include: anchoring the structure against movement by floodwaters, the foundation must be resistant to flood forces and be constructed of flood resistant materials, the lowest floor must be flood-proofed (not permitted for residential structures) or elevated so the enclosed space is at least one foot above the level of the 100-year flood, and all utilities must be resistant to flood damage.