Where sidewalks or curbs have been constructed or repaired without first having obtained a grade and line therefor from the city engineer, or where the same have not been constructed in conformity with the established grade and line or not in conformity with the standard specifications of the city relative to concrete sidewalks and curbs, said sidewalks and curbs shall be rebuilt or repaired at the owner's expense to so conform as provided in this chapter. (1960 Code, Sec. 6-110)