If alterations, repairs, enlargements or additions to a building over any three-year period have a value exceeding 50 percent of the fair market value of the building as determined by the building's assessed valuation or an appraisal prior to commencement of such repairs, alterations, enlargements or additions, under the terms of this subsection, with the exception of buildings destroyed by accidental causes, then the entire building must be renovated to meet applicable building codes, including, but not by way of limitation, all applicable wiring, plumbing, parking, setbacks and construction requirements.