Composite Building Boards with Thermoplastic Coatings and Cementitious Precoated Fibrous Mats

A composite building board comprising:

• a mat including a first portion comprised of a latex based cementitious pre-coating and a polymeric additive, the mat further including a second portion comprised of a series of non-woven, randomly aligned glass fibers, the glass fibers having upper and lower extents, with the upper extents embedded within the pre-coating, a plurality of pores formed within an upper surface of the pre-coating;
• a dense layer of set gypsum penetrating the lower extents of the glass fibers by approximately 90% to 100%, whereby the lower extents of the glass fibers are substantially encased by the dense layer, the dense layer including a polymeric additive;
• a core layer of set gypsum that is bonded to the dense layer, the core layer having a density that is less than the density of the dense layer, the core layer including a polymeric additive that is bonded to the polymeric additive in the dense slurry layer;
• a hot melt thermoplastic coating with a melting point of between 100° F. to 500° F. adhered to the upper surface of the pre-coating, the coating penetrating the pores within the upper surface of the pre-coating to form a mechanical bond between the coating and the mat, the coating bonding to the polymer additive in the pre-coating.