“Demolition” means the destruction, disassembly, dismantling, damage, razing, or tearing down of fifty percent (50%) or more of an existing structure (prior to commencing development) as measured by the finished surface of all exterior wall and roof area above finished grade and associated assembly and components necessary for the structural integrity of such wall and roof area. For the method of determining demolition, see Section 7-308, Measurement of Demolition. The term excludes the sudden or cataclysmic destruction of or damage to a structure due to acts of God, including fire, earthquake, wind, flood, or avalanche.