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 § 69-27 shall apply.
The following provisions shall apply whenever any improvement is made to an existing structure located within any identified floodplain area:
A. 
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. Market value shall be determined using one of the following two sources:
(1) 
The fair market building value as found in the assessment records of Adams County, as maintained by the Adams County Tax Services Department.
(2) 
A fair market value for the building or structure as determined by a qualified independent appraiser retained by the property owner.
B. 
Any modification, alteration, reconstruction, or improvement of any kind occurring as a result of "cumulative substantial damage," as defined in this chapter, shall be undertaken only in full compliance with the provisions of this chapter.
C. 
No expansion or enlargement of an existing structure shall be permitted within a Floodway, A Zone, or AE Zone without floodway that would cause any increase in base flood elevation, and such expansion or enlargement shall be undertaken only in full compliance with the provisions of this chapter.