A nonconforming use or structure may not be enlarged, moved or expanded, increased in intensity, nor may a nonconforming use or structure be changed except to a conforming use or structure. Such prohibited activity shall include the expansion of a nonconforming use within a building or other structure to any portion of the floor area that was not occupied by such legal nonconforming use on the effective date of this chapter, or any amendment to this chapter, which causes such use to become nonconforming.