Facing material with controlled porosity for construction boards

A water-resistant and fire-resistant cementitious board useful in building construction, comprising:

• a layer of set cementitious material sandwiched between a pair of facing layers, at least a first of said facing layers comprising glass fibers bonded together with a resinous binder composition having a hydrophilic or adhesive affinity towards said cementitious material when wet, said first facing layer having an air permeability rating of no greater than about 300 CFM/ft2, so as to substantially prevent penetration of a slurry precursor of said cementitious material having a viscosity of less than 5,000 cp at 70° F., but permit water vapor from said slurry to pass therethrough.

A facing material for cementitious boards useful in building construction, comprising a light weight, relatively dense layer comprising glass fibers, polymeric fibers, or both, and an areal weight of not more than 300 grams/m2, said light weight, relatively dense layer having a tensile strength which is insufficient to provide enough rigidity to withstand the rigors of a continuous cementitious board manufacturing line by itself;

• said light weight, relatively dense layer substantially preventing penetration of a slurry having a viscosity of less than 5,000 cp at 70° F., but permitting water vapor from said slurry to pass therethrough;
• said light weight, relatively dense layer being bonded to a reinforcing scrim, said reinforcing scrim permitting the use of said facing material in said continuous cementitious board manufacturing line without substantial distortion of same.

A facing material for gypsum boards useful in building construction, comprising:

• a first layer including an oriented fiber-containing layer which is porous to a gypsum slurry;
• a second non-woven layer joined to said first layer, said second non-woven layer being less porous to said gypsum slurry that said first layer, and comprising randomly oriented fibers bonded with a resinous binder applied in excess of about 15% by weight of the fibers, said resinous binder does not inhibit adhesion of said facing material to said gypsum, and does not encourage blocking between adjacent pairs of said boards.