The flow regime in a concrete foundation (stem wall and slab) resting on an unsaturated soil was analyzed to determine where and how water moves into and through the foundation in response to water pressures (or moisture suctions) acting at the boundaries. Flow nets were constructed using an iterative, finite difference technique. Steady state conditions and isotropic hydraulic conductivities were assumed in the analyses. Various cases were examined including effects of moisture barriers beneath the foundation and different degrees (or rates) of evaporation at foundation boundaries. An increasingly greater proportion of the total, advective water flow through the foundation occurred into and out of the sides of the stem wall as either 1) upward, water flow into the slab was prevented because of the presence of a moisture barrier beneath the slab, or if 2) a higher amount of evaporation occurred at the outside surface of the stem wall/grade beam compared to the upper surface of the slab. In every case water entering the concrete foundation from irrigated soil adjacent the foundation moved upward and into (and in some cases out of) the grade/beam stem wall. In no case did any of this irrigation water enter the slab. These illustrations and finding are significant with regard to the problem of possible sulfate damage to concrete foundations. The sulfates may occur naturally in the native soil or be introduced in the irrigation water or as sulfates added to the soil from agricultural amendments, e.g. gypsum or sulfur. The illustrations are consistent with the nature of minor damages (e.g., surface flaking and spalling) observed in concrete foundations next to irrigated plantings where sulfates are present in the soil or irrigation water.