This document specifies a method for determining the performance of a preservative, applied to the upper surface of the mortar test specimens, in preventing the growth of dry rot through the treated mortar when exposed to the test fungus. This method is only applicable to masonry fungicides applied as a true solution of the preservative in water or dilute oil in water emulsion. It is not applicable to rods, pastes and other similar preservative types. This method is applicable to preservatives applied to masonry by brushing, spraying and/or injection techniques or mixed into rendering and plastering mortar for masonry.