This invention relates to a method for creating a lightweight cementatious material for use in building construction. The material can be formed in panels to replace conventional drywall gypsum board. In the disclosed form the product does not include any paper or other components that serve as food for mold and therefore is mold resistant. The material has a composition of Portland cement, foamed glass beads and an acrylic co-polymer. In some forms, sand may be used as a filler and in others, the filler may be polystyrofoam particles and vermiculite.