Concrete sidewalks shall be not less than four inches in thickness and five feet in width and shall be poured monolithically with concrete having a 28-day compressive strength of not less than two thousand pounds per square inch. The surface shall be floated true by means of a wood float and shall slope toward the curb not less than one-eighth inch or more than one-fourth inch per foot. The surface shall be marked into squares not less than the width of the sidewalk. Expansion joints shall be provided at junction of sidewalk with curbs, buildings or other permanent objects, and shall be placed not further than 50 feet apart in the length of the sidewalk. All sidewalks, whether placed by contractors or private owners, shall be placed as specified by the city engineer and accepted by him upon completion. Rejected sidewalks shall be patched or broken up and replaced as the city engineer may direct. (Ord. 2763 §10, 1958).