Click on the link below to access the complete FEMA reference manual for information on the "how to's" used to determine substantial improvement or substantial damage when considering any construction or improvements, to any property in a floodplain, whether considerations are due to flood damage or just planning property improvements.
Substantial Improvement (SI) - means any reconstruction, rehabilitation, addition, or other improvement of a structure, the cost of which equals or exceeds 50 percent of the market value of the structure (or smaller percentage if established by the community) before the "start of construction" of the improvement. This term includes structures that have incurred "substantial damage," regardless of the actual repair work performed.
Substantial Damage (SD) - 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 percent of the market value of the structure before the damage occurred. Work on structures that are determined to be substantially damaged is considered to be substantial improvement, regardless of the actual repair work performed.