In no case shall any contract be let either by the city or by the owner, agent or lessee of any lot or parcel of land for the construction of any sidewalk in the city, except that such contractor before doing any work upon such contract shall execute a bond with sureties to be approved by the Board of Officers, payable to the city, which bond shall be in a penal sum equal to 33% of the amount of the costs of such sidewalk to be constructed by such contractor. The bond shall guarantee the construction, workmanship and materials of the sidewalk for a term of three years from the date of the completion of such walk.
('68 Code, § 6.25)