The phenomenon of shrinkage and swelling of fine soils is the cause of several disorders on the structures. Researchers are mainly interested in designing economical foundations that can cope with settlement and swelling movements in these soils. The objective of this study is to study the variation in the permissible stress of fine soils in the locality of Houeyogbe in south-western Benin as a function of moisture content. To accomplish this, we conducted several physical and direct shear tests on fine soil samples collected in the study area, the results of which were used to assess the influence of moisture content. The study of the variation in shear strength of these soils shows that the allowable stress decreases with increasing moisture content. It is therefore imperative to take this parameter into account when dimensioning infrastructures built on these soils.