Patent ID: 7300892

Claim:
A cementitious board for building construction, comprising: a cementitious material layer between two facing layers; the cementitious material layer being formed by solidification of a slurry comprising, cementitious material and water; at least one of the two facing layers comprising, an inner layer having reinforcing fibers, and a porous facing layer having a slurry facing side and an exterior side; a water repellant material on at least the exterior side of the porous facing layer providing the exterior side with water repellency to repel rain and water from the cementitious board, said water repellant material repelling said slurry from penetration through the exterior side of the facing material to prevent slurry contamination on the exterior side of the facing material; the cementitious material layer penetrating the inner layer and the reinforcing fibers; the cementitious material layer being in contact with the slurry facing side of the porous facing layer; a slurry wetting agent on the slurry facing side of the porous facing layer for wetting by the slurry; and pores of the porous facing layer being permeable to evaporated water from the slurry.