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 before the "start of construction" of the improvement. This term includes structures which have incurred "substantial damage," regardless of the actual repair work performed. The term does not, however, include either:

• Any improvement of a structure to correct existing violations of state or local health, sanitary, or safety code specifications which have been identified by the local code enforcement official and which are the minimum necessary to assure safe living conditions or
• Any alterations of a "historic structure," provided that the alteration will not preclude the structure's continued designation as a "historic structure."

Floodplain management requirements for new construction apply to substantial improvements.

It is essential to check with the City before you make any improvements, additions, extensions, or remodeling to your home particularly if the building is in the floodplain. Almost all repairs and remodeling work requires a permit. Buildings located in the flood plain may need additional permits from FEMA.

For more information please check FEMA website.