(a) Nothing in this part shall be construed to prevent the ordinary maintenance or repair of any exterior architectural feature within the boundaries of an historic property which does not involve a change in the appearance or design thereof; nor to prevent the erection or alteration of any such feature which the building inspector or a similar agent certifies is required by the public safety because of a condition which is unsafe or dangerous due to deterioration; nor to prevent the erection or alteration of any such feature under a permit issued by a building inspector or similar agent prior to designation of such historic property.

(b) If a building within the boundaries of an historic property is to be demolished, no demolition shall occur for ninety days from issuance of a demolition permit if during such time the historic properties commission or the Department of Economic and Community Development is attempting to find a purchaser who will retain or remove such building or who will present some other reasonable alternative to demolition. During such ninety-day period the municipality may abate all real property taxes. At the conclusion of such ninety-day period, the demolition permit shall become effective and the demolition may occur. Nothing in this section shall be construed to mandate that the owner of such property is under any obligation to sell such property or building.