A legal nonconforming building that has been or may in the future be damaged or destroyed by fire, explosion, or other casualty or act of nature, or public calamity or riot, may be reconstructed to its original density, size, height, design, configuration or condition and the use or occupancy of such building or part thereof which existed at the time of such destruction may be continued provided such legal nonconformities are not increased in density or intensity, and there is no reduction in the amount of off-street parking and landscaping that existed onsite prior to such destruction.