All sidewalks laid after 1953 shall be of uniform width, lines and grade; provided that no sidewalk of less width than five feet shall be constructed except to connect with a four-foot concrete sidewalk previously laid and accepted. In the Pine Acres Subdivision to the city it shall be lawful to construct sidewalks three feet in width. All sidewalks shall be of concrete. Any sidewalk or pavement which does not conform substantially to the grade, or line, or to the materials and workmanship required, is declared to be a nuisance, and the person building the same, or the owner of the adjoining premises, shall remove the same on five days' notice from the City Engineer. In such case, the walk may be summarily removed and reconstructed by the city, and the expense collected from the property owner.
('68 Code, § 6.25)