Soil is a sustainable construction material that has been used traditionally for thousands of years. In general, earth construction specifications are based on common knowledge. Existing recommendations tend to be supported by a limited number of studies and depend on local materials, climatic conditions and historical background. The lack of understanding of compacted soil behavior, in particularly its strength, may have prevented a wider application of earthen construction materials in housing. Understanding of the soil properties and parameters that influence its performance when used in walls and columns is essential for interpretation of experimental data. Recently a number of studies have analyzed rammed earth considering unsaturated soil mechanics, which suggest loss of strength following decrease in suction values, for example provoked by the increase in relative humidity. However, there is a lack of such research pertaining to compressed earth blocks (CEBs). The objective of this study was to verify the influence of clay content, density and suction on the strength of CEBs. Four soil mixes consisting of sand, quartz powder and kaolinitic clay were used. For each soil mix statically compacted samples with densities corresponding to optimum and dry of optimum moisture contents were tested for a range of suctions. Unlike reported in the literature, the results showed loss of strength following increase in suction values, while only small variations were registered for suctions corresponding to a wide range of RH and temperature conditions. The findings can be of use for specifications relating to construction of sustainable housing using CEBs.