kg cm cm 2 of the impact strength a fiber reinforced cementitious substrate prepared by the sheeting operation using 5 wt of slag wool 4 wt of asbestos 4 wt of pulp and the remainder of portland cement had 125 kg cm 2 of the bending strength and 3 kg cm cm 2 of the impact strength both of the bending strength and the impact strength were remarkably lower than those of the products wherein polypropylene fiber or slag wool was substituted with glass fiber as shown in table 1 when 1 to 10 wt of glass fiber 1 to 10 wt of asbestos 0 to 10 wt of pulp and the remainder of the cementitious material were blended to prepare each slurry and each wet film was formed by the sheeing operation and each green sheet was prepared by taking up the wet film on a making roll the sheeting characteristic was excellent without remakable decrease of the vat level and without remarkable increase of solid content in the discharged water and without falling down of the wet film the resulting glass fiber reinforced cementitious substrates had excellent bending strength and impact strength without peeling off as shown in experiments nos 4 5 12 18 19 22 23 and 24 it is preferable to use mixtures of 2 to 8 wt of glass fiber 2 to 5 wt of asbestos 1 to 7 wt.