The purpose of this study is to manufacture mortars incorporating oyster shells and install them in the form of shaped, shaped butt joints, and flat boards to see what difference there is in the back temperature depending on the joint method and the type of installation. Based on the fact that similar backside temperatures were measured regardless of the presence or absence of a joint It is judged that the joint will not affect the backside temperature if it is constructed closely, In the case of ㄱ shaped, it is believed that the backside temperature higher than the backside temperature of the flat board was measured because heat accumulates on the backside during heating.