Where and when the work contemplated and authorized by such permit shall have been timely commenced, all such work shall be completed within 12 months of the date of issuance of such permit or such permit shall automatically expire by limitation; and in such case and circumstance all further or additional work shall cease and desist unless and until a renewal permit has been applied for and granted by the Building Department. In the event that a renewal permit is approved, then, upon the payment of an additional renewal fee equal to 75% of the original permit fee, such renewal permit shall be issued for, and all work covered by and under such permit shall be completed within, six months of the date of issuance of such renewal permit. In the event that all work is still not completed within such renewal period, then an additional renewal permit must be obtained from the Building Inspector; and in each event of additional renewal, the renewal permit shall be valid for a period of three months from the date of its issuance and shall be subject, in each case, to the payment of an additional renewal fee equal to 50% of the original permit fee. Renewal permits shall be required for any and all periods following the expiration of the original permit and expiration of any subsequent renewals thereof. The duration of the original permit and any subsequent renewals shall not exceed a total period of 24 months. Upon the expiration of said twenty-four-month period, a new application must be made to the Building Department for the issuance of a building permit.