ABSTRACT
Both gypsum and Portland cement plasters can be applied directly to concrete and masonry surfaces that have sufficient bonding capabilities. The surfaces should be clean (no grease, paint, efflorescence, waterproofing compounds), firm, and sound, and should provide adequate suction for a good bond. When the bonding capabilities are in question it is recommended to use a dash bond coat made of one part cement and two parts of fine sand by volume. The dash coat is applied with a small straw broom and should not be troweled. Another method to improve the bonding on concrete or masonry is to apply a waterproof bonding agent for exterior surface use.
