Sidewalks shall be constructed of the best quality of Portland cement concrete and shall be of such composition as may be specified by the city engineer. No sidewalks shall be constructed of boards, planks or wooden materials. No work shall be done on any sidewalk or curb, except with strict compliance with the specifications compiled by the city engineer, and all materials and work shall comply with the specifications furnished by the city engineer. (1960 Compilation § 14-106)