BUILDING AND STRUCTURAL BOARD MATERIAL

PROBLEM TO BE SOLVED: To enable a board material to be used as an external facing for a structure with high durability and water resistance, exposed to the weather and sunshine by forming a coating film layer on the surface of a fiberboard with a medium specific gravity obtained by bonding and molding split wood fibers with a melamine resin. SOLUTION: A fiberboard 10 is obtained by adding a synthetic resin adhesive of a melamine-urea co-condensation resin to wood fibers obtained by filbrillating wood and molding the mixture into a board shape. The coating film layers 20, 20 are formed by sequentially applying an undercoat, an intercoat with a grain pattern and a topcoat on both faces of the fiberboard 10. The composition of the undercoat is an acrylic resin emulsion, while and extender pigments, water, an additive, a colored pigment or the like. The composition of principal ingredients of the intercoat is the acrylic resin emulsion, water, additive, crushed grains of natural stone, colored aggregates or the like. The composition of the topcoat is a modified silicone resin varnish, the additive, a solvent or the like. Thus it is possible to use this building and structural board material as an external facing for a building or a structure exposed to the weather and sunshine on account of the improved durability and water resistance of the board material.