The purpose of this study is to investigate the carbonation resistance of building coating materials applied to the mortar or concrete substrate including their cracked zone. The testing parameters for this experiment were the three crack widths in the substrate including non-crack, and two types of the coating materials. As results, the coating materials have good carbonation resistance against $CO_2$ penetration into mortar substrate even in cracked zone of substrate. Furthermore, the carbonation resistance of coating material was calculated by using their $CO_2$ permeability coefficient and discussed from viewpoint of durability design.