Nothing contained in this chapter shall require any change in the plans, construction or designated use of a building for which a building permit has heretofore been issued or plans for which are on file with the Construction Official at the time of the passage of this chapter and the permit for the erection of which is used within three months of the passage of this chapter and the construction of which, in either case, shall have been diligently prosecuted within three months of the date of such permit and the ground story framework of which, including the second tier of beams, shall have been completed within a year of the date of such permit, and which entire building shall be completed according to such plans as filed within two years from the date of the passage of this chapter.
Nothing in this chapter shall prevent the restoration of a structure partially destroyed by fire, neglect or otherwise subsequent to the passage of this chapter or prevent the continuance of the use of a building or part thereof existing at the time of such destruction. Nothing in this chapter shall prevent the restoration or removal of a wall or any part of a building declared unsafe by the Construction Official.