A composite fabric for use in reinforcement, particularly tensile reinforcement, of cementitious boards and similar prefabricated building wall panels. The fabric is constructed as a mesh of continuously coated, high modulus of elasticity strands. The high modulus strands are preferably bundled glass fibers encapsulated by alkali and water resistant thermoplastic material. The composite fabric also has suitable physical characteristics for embedment within the cement matrix of the panels or boards closely adjacent the opposed faces thereof. The fabric provides long-lasting, high strength tensile reinforcement of the panels or boards regardless of their spatial orientation during handling. The reinforcement also enhances the impact resistance of the boards after installation. Included as part of the invention are methods for making the reinforcement, cementitious boards and panels including the reinforcement, and methods for manufacturing such boards and panels.