ABSTRACT: The masonry compressive strength depends on a number of parameters. The unit compressive and tensile strength, the joint compressive strength, the ratio of the radical strain coefficients and also the moduli of elasticity of unit and mortar as well as the bond behaviour can be specified as possible primary influencing parameters. Some of these, however, depend on secondary influencing parameters, such as the suction behaviour of the units and the water retention of the mortars related to the mechanical properties of the joint mortar. In the past, many attempts were made to derive the masonry compressive strength empirically depending on the unit and mortar compressive strength. In doing so, the compressive strength of the mortar hardened in steel formworks was applied, although it is known that it can deviate significantly from the mortar compressive strength in the bed joint. Therefore, it is the aim to develop an engineering model to predict the masonry compressive strength which, in addition to considering the relevant material characteristic values, also includes the hygric interaction between unit and mortar. In the first step, the masonry components were examined and their relevant properties were determined with or without taking into account the contact between mortar and unit. The focus was mainly set on investigating the mortar properties depending on different initial moisture contents of the masonry units and the time. To completely describe the effects of water absorption, the porosity of the mortar samples was additionally determined by means of the water absorption method. Furthermore, the influence of the water suction on the compressive strength of small masonry pillars was examined.