Nothing in the within section shall be construed so as to prevent the strengthening or restoration to a safe and lawful condition of any part of a building declared to be unsafe or unlawful by the Construction Official, Fire Department or other duly authorized official. Such repairs and maintenance work as required to keep it in sound condition may be made to a nonconforming building or structure, provided that no structural enlargements shall be made. All alterations shall be in accordance with the requirements of the State Uniform Construction Code and the area, bulk and other requirements of the within zoning chapter, or any amendment or supplement thereto, specifically referring to the zone location of the nonconforming premises.