In the event of loss or damage, when an agreement as to the extent of such loss or damage cannot be arrived at between the board and the officials having charge of the property, the amount of such loss or damage to be paid by the board shall be determined by three appraisers, one to be named by the board, one by the officer, official or trustee having the damaged or destroyed building in charge, and the third by the two so appointed. These appraisers shall file their written report with the board and a duplicate copy with the insured. The cost of the appraisal shall be borne one half by the board and one half by the insured.