The board of county commissioners, in case of each improvement ordered by it, shall designate the place of beginning and the direction in which the work must proceed, and shall require the same to be completed mile [1.61 kilometers] by mile [1.61 kilometers] or in parts of miles [kilometers] continuously, as ordered, and no payment may be made except for work so completed. It also may require the supervision of the work by the county surveyor, so far as deemed necessary, and shall require the county surveyor to compute and estimate the amount of completed work and to certify the same to the county auditor at the end of each month, and all the work contracted for must be completed prior to the first day of November next following. The provisions of this section and the orders and directions of the board made in pursuance thereof must constitute a part of the provisions and conditions of every such contract, whether expressed therein or not.