Method of forming a reinforcement sheet to reinforce a cementitious board

A method of making a reinforcement sheet for a cementitious board comprising:

• applying a hydrophilic coating material on binder coated glass fibers wherein the non-interlaced glass fibers are accumulated in random or selected orientations and are coated with a binder that adheres the glass fibers together by curing prior to applying the hydrophilic coating material on the binder coated glass fibers, the hydrophilic coating material being mobile in slurry water to dilute and disperse upon contact by surface molecules of the slurry water at a surface of a slurry of a cementitious compound to dilute and disperse, and to wet and spread the slurry on the binder coated glass fibers, and the hydrophilic coating material being volatile to dissipate by evaporation at an elevated temperature at which the cementitious compound is dried for the binder coated glass fibers to be essentially free of the hydrophilic coating material as a source of water and moisture absorption to provide a water vapor porous layer with a hydrophobic surface.