The provisions of this chapter do not require any changes or improvements to be made to lawfully existing structures. However, when an improvement is made to any existing structure, the provisions of § 97-32 shall apply.
The following provisions shall apply whenever any improvement is made to an existing structure located within any identified floodplain area:
A. 
No expansion or enlargement of an existing structure shall be allowed within any floodway area that would cause any increase in the elevation of the one-hundred-year flood.
B. 
No expansion or enlargement of an existing structure shall be allowed within any FE area that would, together with all other existing and anticipated development, increase the one-hundred-year-flood elevation more than one foot at any point.
C. 
Any modification, alteration, reconstruction, or improvement, of any kind to an existing structure, to an extent or amount of 50% or more of its market value, shall constitute a substantial improvement and shall be undertaken only in full compliance with the provisions of this chapter.